TRUNKING CONCEPTS TRUNKING CONCEPTS Introduction This training program covering Trunking Concepts is intended to provide customer technicians the prerequisite knowledge required for the SmartZone and SmartZone OmniLink training programs. Although the main audience intended for this training is Motorola, customer, and dealer/MSS technicians, the first five modules may be appropriate for other audiences such as Motorola/Dealer sales personnel, customer management and administrative personnel, and others with a need to learn Motorola trunking concepts. The remaining modules (6 - 8) are more detailed and technically oriented and may not be appropriate for all audiences. Module Titles Module 1. Introduction to Trunking 1-3 Module 2. How Trunking Works 2-1 Module 3. Trunked Call Types 3-1 Module 4. Trunked System Features 4-1 Module 5. Private Trunked Systems 5-1 Module 6. Trunking Signaling 6-1 Module 7. Type I vs. Type II Trunking 7-1 Module 8. System ID Structure 8-1 Motorola Confidential 1-1 V.1.0
This training program covering Trunking Concepts is intended to provide customer technicians the prerequisite knowledge required for the SmartZone and SmartZone OmniLink training programs. Although the main audience intended for this training is Motorola, customer, and dealer/MSS technicians, the first five modules may be appropriate for other audiences such as Motorola/Dealer sales personnel, customer management and administrative personnel, and others with a need to learn Motorola trunking concepts. The remaining modules (6 - 8) are more detailed and technically oriented and may not be appropriate for all audiences.
Module 1. Introduction to Trunking 1-3
Module 2. How Trunking Works 2-1
Module 3. Trunked Call Types 3-1
Module 4. Trunked System Features 4-1
Module 5. Private Trunked Systems 5-1
Module 6. Trunking Signaling 6-1
Module 7. Type I vs. Type II Trunking 7-1
Module 8. System ID Structure 8-1
Upon completion of this segment of the training, the learner should be able to:
Define trunking. Describe the advantages of trunking. Identify the FCC loading requirements for trunked systems. Explain how users are organized in a trunked system. Identify the components that comprise a basic trunked system. Explain the basic functionality of a trunked system and how a call is processed. Differentiate between message trunking and transmission trunking. Describe trunked system access features. Describe the timeout parameters used in a trunked system.
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Describe the trunked system reliability features. Describe each of the trunked systems types provided by Motorola. Describe the Voice on Control (VOC) operation available in Motorola trunked
systems. Describe the ID structure used in a trunked system.
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Module 1: Introduction to Trunking
Topic 1: Trunking Concepts 1-4This topic introduces the concept of trunked systems and shows how non-trunked and trunked systems compare.
Topic 2: Trunking Features and Advantages 1-8This topic describes important features and advantages of Motorola trunked radio systems.
Activity 1-10In this activity, you will match features and advantages of trunked radio systems with their descriptions.
Topic 3: Channel Loading Criteria 1-11This topic describes FCC requirements for channel loading in two-way radio communication systems.
Module Exercises 1-12This module ends with exercises that test your mastery of module objectives.
The purpose of this module is to provide a definition of trunking and to introduce the learner to the advantages of trunking over other types of two-way communication. This module will also explain the FCC loading requirements for a trunked system.
Define trunking. Describe the advantages of trunking. Identify the FCC loading requirements for trunked systems.
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Topic 1: Trunking Concepts
Trunking is a telephone company concept that refers to the automatic sharing of a small number of communications paths among a large number of telephone subscribers. In two-way radio communications, trunking refers to the automatic and dynamic sharing of a small number of radio channels between a large number of radio users.
A trunking system efficiently distributes message traffic among the available channels and reduces channel waiting time.
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Non-Trunked Communication System
Compare a non-trunked communication system to a group of toll booths on a toll highway. Red cars must use the red both, green cars must use the green booth, and blue cars must use the blue booth.
As long as there are about the same number of cars of each color, the toll booths are used efficiently.
A number of red cars may stack up waiting for the red booth to become available. Even though there are no green or blue cars, the red cars must wait because they can use only the red booth.
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Trunked Communication System
Compare a trunked communication system to the system many airlines use to handle queuing for ticket agents. Any agent can handle a transaction for any user. There is a single queue, and each user is handled by the next available ticket agent.
If there are fewer users than ticket agents, there is no waiting.
If there are more users than ticket agents, a single queue builds up. The single queue gives all users equal access to the available ticket agents.
The effectiveness of trunking is predicated on two fundamental characteristics of user communication:
It is improbable that a large percentage of users will want to make a call at the same time.
Most conversations are relatively short.
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Topic 2: Trunking Features and Advantages
The graphic below lists a number of features and advantages of Motorola trunked radio systems. These features and advantages are described in the following sections.
Faster System Access
Users have faster system access since all repeaters in the system are typically made available to all users. In addition, voice channels are assigned automatically, eliminating the need for the user to monitor and wait for a clear channel
Better Channel Efficiency
All channels are typically shared by all users, resulting in an overall decrease in channel congestion.
Groups of users can be assigned exclusive use of a voice channel for the duration of a conversation. Users in other groups cannot listen to that channel.
Types of Communication
Users can initiate a wide variety of calls including one-to-one, one-to-many, and one-to-all.
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The queuing capabilities of a trunked system provide a more orderly approach to system access. A feature called new user queueing makes it possible for the radio user to set down the microphone and wait for a call back once a busy signal has been received. This relieves the user from having to continually rekey the PTT button in order to gain system access.
Automatic retry eliminates the need for a user who is experiencing bad signalling conditions or interference to continually key and dekey the radio in order to gain system access.
Provision for different levels of priority ensures that critical users have more immediate access to the system. A feature called recent user priority ensures that ongoing communications can be completed on a priority basis over conversations that are just being initiated.
Additional users can be added without necessarily adding additional channels or modifying existing radios.
Continuous Assignment Updating
The continuous assignment updating feature ensures that a radio just coming into service in the middle of a conversation will immediately be assigned to the appropriate voice channel so that the user can be included in that conversation.
User Call Organization
The user call organization feature allows a user to organize the radio system around functional, or operating groups, rather than according to frequencies or channels.
The Failsoft feature ensures continued communications capability in the case of a malfunction of the central controller. System operation reverts to operation in a non-trunked system in which talkgroups are assigned to fixed voice frequencies.
Match each of the following features and advantages of trunking with the statement that best describes it.
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Features and Advantages:
A. User PrivacyB. QueuingC. Automatic RetryD. Priority LevelsE. Continuous Assignment UpdatingF. Fail Soft
B Allows a user to wait for a call back after a busy signal has been received. C Avoids the need to continually key the radio in order to gain system access when experiencing signal problems.F Ensures continued communications capability in the case of a malfunction of the central controller.A Allows different groups of users to be assigned exclusive use of a voice channel for the duration of a conversation.D Provides critical users with more immediate access to the system than non-critical users.E Ensures that a radio just coming into service in the middle of a conversation will immediately be assigned to the appropriate voice channel.
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Topic 3: Channel Loading Criteria
The FCC assigns radio frequency channels to users based on an expectation that those channels will be effectively utilized. The FCC considers a fully-loaded channel to be one that serves 100 users.
When the FCC grants a 5-channel license the system owner has 2 years to accomplish 70% loading. This means that within 2 years, the system owner must be serving at least 350 users with those five channels.
When the FCC grants a 20-channel license the system owner has 5 years to accomplish 70% loading. This means that within five years, the system owner must be serving at least 1,400 users.
The FCC may delete channels if the system owner is not able to accomplish 70% loading in the allotted time.
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In a trunking system, repeaters are used in the following manner:
a. Each user is assigned to a particular repeater.b. Each talkgroup is assigned to a particular repeater.c. All users share a common pool of repeaters. d. Only one repeater is used.
Which of the following trunking features allows a user to be assigned to the correct voice channel no matter when he or she enters a conversation:
a. Automatic retry.b. Continuous assignment updating.c. User privacy.d. Failsoft.
With a 20-channel license, the FCC requires the system owner to accomplish:
a. 70% loading within 5 years.b. 90% loading within 2 years.c. 70% loading within 2 years.d. 50% loading within 3 years.
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Module 2. How Trunking Works
Topic 1: Talkgroups and Announcement Groups 2-3This topic explains how radio users are grouped into collections called talkgroups and announcement groups.
Topic 2: User Organization Example 2-7This topic shows an example of a possible talkgroup and announcement group organization.
Topic 3: Trunking Infrastructure 2-9This topic shows how the equipment that implements a Motorola trunked radio system is organized.
Topic 4: Trunking Calls 2-11This topic introduces the way in which calls are handled in a Motorola trunked radio system.
Topic 5: Basic Call Processing 2-15This topic follows a trunked call from initiation to completion.
Activity 2-24In this activity, you will place basic call processing steps into the sequence in which they are performed.
Topic 6: Busy Call Processing 2-25This topic shows how a call is handled when there are no system resources available to handle it.
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In this activity, you will place busy call processing steps into the sequence in which they are performed.
Topic 7: Message and Transmission Trunking 2-30This topic explains the difference between message trunking and transmission trunking.
Module Exercises 2-35This module ends with exercises that test your mastery of module objectives.
The purpose of this module is to provide a high-level overview of how trunked system users are organized, the components that comprise a basic trunked system, and how a trunked system processes basic talkgroup calls. This module will also describe the difference between transmission and message trunking.
Explain how users are organized in a trunked system. Identify the components that comprise a basic trunked
system. Explain the basic functionality of a trunked system and
how a call is processed. Differentiate between message trunking and
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Topic 1: Talkgroups and Announcement Groups
The concept of talkgroups underlies the way in which users are organized in a trunked communication system.
The basic unit of organization in a trunked communication system is the individual radio user.
Each radio in a trunked communication system has a unique identifier assigned to it called a Unit ID.
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To simplify the diagrams, each radio will be identified with a simpler one-digit Unit ID.
Individual users can be combined into collections called talkgroups. The first collection of two users forms one talkgroup.
The second collection of three users forms a second talkgroup.
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Each talkgroup in a trunked communication system has a unique identifier assigned to it called a Talkgroup ID.
Most calls that take place in a trunked communication system are ordinary talkgroup calls. When a user makes a talkgroup call in a trunked communication system, all radios in that talkgroup hear that call. Other users not in that talkgroup do not hear the call.
A talkgroup is made up of a collection of users who typically need to communicate in order to accomplish their job. The users in a particular talkgroup usually have a common functional responsibility. Typically, the majority of an individual's communications requirements will be to communication with other users in his or her own talkgroup.
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Motorola trunking allows multiple talkgroups to be dynamically merged into larger groups called announcement groups. Announcement groups are sometimes called multigroups.
When a radio user places an announcement group call in a trunked communication system, that call is received by all the radios in all the talkgroups associated with that announcement group. Announcement groups ensures that critical information is received at once, by as many talkgroups as desired, throughout an entire system.
In defining the user organization for the system, not every talkgroup needs to be included in an announcement group.
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Topic 2: User Organization Example
As an example of trunking user organization, assume there are two departments within a Public Works Department: a Highway Department and a Maintenance Department.
Highway and Maintenance Talkgroups
Since it is likely that all the radio users in the Highway Department need to be in communication with one another, they might be grouped into a talkgroup. Call this one Talkgroup A.
It is also likely that all the radio users in the Maintenance Department also need to communicate frequently, they may form another talkgroup. Call this one Talkgroup B.
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Overlapping Supervisor Talkgroup
It is also likely that the supervisors in both the Highway Department and the Maintenance Department will need to communicate frequently. One radio in each talkgroup is used by a supervisor
The supervisors can form a third, overlapping talkgroup. Call this one Talkgroup C. As this example shows, each individual radio user can be assigned to multiple talkgroups. The user selects the particular talkgroup to use for communication by selecting appropriate settings on the radio.
Highway/Maintenance Announcement Group
Should the need arise, talkgroups A and B could be merged into a single announcement group, along with any other desired talkgroups. With such an announcement group, a radio user in the Highway Department can originate a call that is heard by users in both the Highway Department and the Maintenance Department.
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Topic 3: Trunking Infrastructure
The backbone of a Motorola trunked radio system begins with a series of trunked repeaters located at a location chosen to assure optimum coverage. A single-site Motorola trunked system can support up to 28 repeaters. The example shows only five repeaters for simplicity.
Trunked repeaters are capable of handling data traffic as well as voice traffic. In a Motorola trunked system, one repeater always has the duty of transmitting and receiving the data traffic required to monitor and control the operation of the system. The repeater performing this duty is called the control channel. All the other repeaters are designated as voice channels. The first four repeaters in a trunked system are capable of performing control channel duty, with only one of those repeaters at a time actually performing the control channel function.
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A Motorola trunked radio system also uses a central controller that functions like a traffic cop and controls the operation of the trunked repeaters. The central controller is a computer that processes inbound and outbound data traffic, assigns repeaters for voice channel access, and generally monitors and maintains order in the system. All of the repeaters are linked to the central controller via dedicated data cables.
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Assume that the users who will be making use of this trunked radio system are organized into two talkgroups: Talkgroup A and Talkgroup B. The talkgroup may contain a mixture of mobile and portable radios. All of the radios are trunked radios that are frequency synthesized and capable of switching to the frequencies of any of the repeaters in the system. Each radio is capable of transmitting a unique code word that identifies the radio to the central controller and indicates to which talkgroup the radio belongs.
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Topic 4: Trunking Calls
Topics 4, 5, and 6 in this module show how a trunked system controls the call processing sequence throughout all phases of a call, from the system being in the idle state, to processing a request for a call, to assignment of a voice channel for completion of a call.
This example follows a typical call from the moment before access is requested until the conversation is completed. In this example, repeater 1 is operating as the control channel, and the trunking system is in idle state.
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When the system is in Idle Mode, no radio users are talking and all radios are monitoring the control channel. The radio speakers are muted since only data transmissions being received. In Idle Mode, the central controller uses the control channel to periodically send out a data signal called a System Status Word (SSW). The SSW contains system identification information and is transmitted at least every three seconds. The SSW is received by all radios and tells them which channel to monitor as the control channel.
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Central Controller Database
The radios used in a Motorola trunked system are microcomputer controlled. Each radio has information programmed into it that determines its personality and specifies the radio’s Unit ID.
The central controller maintains a database that keeps track of each radio’s Unit ID and the talkgroups with which each radio is currently affiliated.
Assume this radio is first turned on in this trunked communication system.
The radio reads from its memory a list of possible control channels.
The radio then scans these channels looking for a System Status Word. When a radio receives an SSW, it compares the System ID value in the SSW with the System ID information in the radio’s memory.
If the system ID values match, the radio is in the correct trunking system and continues to monitor the channel transmitting the SSW. If the system ID values do not match, the radio continues to scan all the control channels listed in its memory until it receives an SSW that has the proper System ID value.
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If the radio does not receive an SSW with a matching System ID, the radio continues scanning. This may occur because the radio may be out of range of its trunking system. As the radio continues to scan the control channel frequencies, it may eventually come into range of its own system. When that happens, it receives an SSW with a System ID match and then proceeds to operate normally.
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Topic 5: Basic Call Processing
Initiating a Call
The central controller continually monitors the control channel to see if a radio user wants to make a call. All of this is done without the involvement of the radio users.
This topic shows a request for a call. In this example, radio 5 in talkgroup B is initiating a request to make a call in the trunked system.
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Inbound Signal Word
When the radio user presses the PTT button, the radio sends a data signal in the form of an Inbound Signal Word (ISW) to the control channel. The ISW contains the radio’s Unit ID and an indication of the type of call being made. In this example, the call is a talkgroup call. The ISW constitutes a request for allocation of a voice channel for the call.
There is a possibility that the ISW may not get through because of weak signalling conditions or interference. To prevent this, the radio uses a feature called Automatic Retry and continues sending ISWs until the receipt of the ISW is acknowledged by the central controller, up to 16 times randomly within 4 seconds.
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Call Processing Event Sequence
Once the control channel receives an ISW from a radio in the system, the following sequence of events takes place. The entire sequence of events occurs in less than half a second.
Step 1 -- Central Controller Receives Call Request ISW
The control channel forwards the received ISW to the central controller.
The central controller then searches its data base for a Unit ID match.
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The ISW contains the selected talkgroup information. The central controller updates the database to reflect the current talkgroup affiliation.
Step 2 -- Central Controller Transmits OSW
The central controller processes the ISW and assigns one of the idle repeaters to the user’s talkgroup. In this case, Repeater 5 is assigned.
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The central controller the sends an Outbound Signal Word (OSW) over the control channel. The OSW contains the Talkgroup ID and Unit ID of the requesting radio, as well as voice channel assignment information.
Step 3 -- Radios Receive OSW
All radios monitoring the control channel receive the transmitted OSW and examine the Talkgroup ID contained in the OSW.
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Step 4 -- Radios Switch to Voice Channel Frequency
All of those radios assigned to the talkgroup associated with the Talkgroup ID in the OSW switch to the assigned voice channel frequency.
Step 5 -- Central Controller Transmits LSHS Signal
The central controller now sends a Low-Speed Handshake Signal (LSHS), sometimes called a Connect Word, over the voice channel. All radios that have switched to that voice channel receive the LSHS. The LSHS unmutes the receiving radios to allow them to receive the incoming transmission.
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Step 6 -- Initiating Radio Transmits Voice and Connect Tone
The initiating radio transmits voice audio and a sub-audible Connect tone. The Connect tone is used to inform the central controller of voice channel activity.
Step 7 -- Central Controller Continues Transmitting LSHS Signal
The central controller continues to send the LSHS on the assigned voice channel for the duration of the transmission. This is used to keep the receiving radios unsquelched.
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Step 8 -- Disconnect Tone
When the radio user releases the PTT button, the radio transmits a Disconnect tone to the central controller, indicating that the transmission has ended
Step 9 -- Radios Switch Back to Control Channel Frequency
When the call is completed, the radios in the talkgroup switch back to the control channel frequency.
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All the radios continue to receive the SSW from the central controller. The previously assigned voice channel now becomes available for other calls.
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Other Call Processing
While the talkgroup B conversation is in progress, any radio in another talkgroup can also initiate a call and will be assigned an available voice channel in the same manner.
In addition, the central controller continues to transmit OSWs over the control channel. The OSWs contain the voice channel assignments for all active calls. This information is used by any radio that may be turned on, or come into range, after a call is in progress.
When a new radio is first turned on while a call for its talkgroup is in progress, a process called Continuous Assignment Updating is used to find the proper control channel, receive the OSWs being transmitted, and switch to the appropriate voice channel to join its talkgroup.
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Enter numbers to the left of each of the following steps involved in call processing to place the steps into the sequence in which they are performed.
6 All radios in the talkgroup are unsquelched. The initiating radio is unmuted and transmits voice information and a Connect tone.3 All radios monitor the OSW and examine the Talkgroup ID.1 A radio transmits a Call Request ISW, the control channel forwards the ISW to the central controller, and the control channel retrieves an entry for the initiating radio from the talkgroup database.4 All radios in the requesting radio's talkgroup switch to the assigned voice channel.2 The central controller processes the ISW, assigns an idle repeater to the requesting radio user's talkgroup, and sends an OSW to the requesting radio indicating the voice channel to use. 5 The central controller sends an LSHS signal over the assigned voice channel, which all the radios in the talkgroup receive.
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Topic 6: Busy Call Processing
The events described in Topic 5 occur if a voice channel is available at the time a request for access is received by the central controller. This topic describes the events that take place during busy periods when there are no voice channels available.
Assume a user tries to access the system and all repeaters are in use, which indicates there are no available voice channels.
Step 1 -- Central Controller Receives Call Request ISW
The radio requesting a call sends an ISW in the normal manner.
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Step 2 -- Central Controller Finds No Available Voice Channel
The control channel receives the ISW and forwards it to the central controller. The central controller processes the call request and determines that there are no available voice channels.
Step 3 -- Central Controller Transmits Busy OSW
The central controller transmits an OSW to the requesting radio, indicating that the system is busy. This causes the requesting radio to generate a busy tone.
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Step 4 -- Central Controller Queues Call Request
The central controller places a call request entry in a Busy Queue. where it remains until a voice channel becomes available. Additional radio users can also make call requests, and entries for all call requests are placed in the Busy Queue on a first-in-first-out basis.
Step 5 -- Repeater Becomes Available and Call Completes
Now repeater 3 becomes available.
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The central controller next retrieves the call request entry from the queue. The central controller then transmits another OSW containing Voice Channel assignment information. All the radios in the talkgroup receive the OSW and switch to the assigned voice channel. The requesting radio generates another tone notifying the user that a voice channel has become available. The originating radio user then begins the call.
The call is then processed as described in Topic 5.
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Enter numbers to the left of each of the following steps involved in busy call processing to place the steps into the sequence in which they are performed.
2 The control channel receives the ISW and forwards it to the central controller. The central controller processes the call request and determines that there are no available voice channels.3 The central controller transmits an OSW to the requesting radio, indicating that the system is busy, which causes the requesting radio to generate a busy tone.1 A radio transmits a Call Request ISW, the control channel forwards the ISW to the central controller.4 The central controller places a call request entry in a Busy Queue. where it remains until a voice channel becomes available.5 A repeater becomes available. The central controller retrieves the call request entry from the queue and transmits an OSW containing Voice Channel assignment information. Radios in the talkgroup receive the OSW and switch to the assigned voice channel. The initiating radio user begins the call.
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Topic 7: Message and Transmission Trunking
There are two forms of trunking that can be used in a Motorola trunked system:
Message Trunking Transmission Trunking
Motorola trunked systems can be set up for message trunking or transmission trunking depending on the user’s requirements.
In this sequence, assume the central controller is using repeater 3 to handle voice transmission involving radio 1 in talkgroup A.
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During the time that a radio is transmitting, the radio transmits voice information and also transmits a Connect tone to the central controller.
The assigned repeater handles the voice information and transmits a Low-Speed Handshake Signal (LSHS) to the radio.
When the radio user releases the PTT button, the radio transmits a Disconnect tone to the central controller indicating that the transmission has ended.
The most apparent difference between message trunking and transmission trunking is what happens after the user releases the PTT button and the radio transmits the Disconnect tone.
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With Message Trunked calls the central controller gives other users a chance to respond to each transmission that takes place. When a radio user releases the PTT button, the Central Control receives the Disconnect tone and starts a message trunked timer.
The central controller continues handling the voice and transmitting the LSHS signal.
While the drop-out timer is running, the central controller continues to send the LSHS tone. During the drop-out time, if a member of the talkgroup presses the PTT button, the radio will unmute and immediately begins transmit a voice signal along with a Connect tone. Communication then continues on the previously established voice channel.
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Now look at another call example.
The radio user releases the PTT button, and the radio again sends the Disconnect tone.
The central controller now starts the message trunked timer again.
If no calls are made, the drop-out timer eventually expires. When that happens, the central controller stops sending the LSHS tone and transmits a Disconnect signal. The radios in the talkgroup then squelch and revert back to monitoring the control channel OSW.
Message trunking is the preferred mode of communication in most Motorola trunked systems. Message trunking maintains a smooth flow of conversation with few in-terruptions by other system activity.
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The following sequence shows an example of transmission trunking. Again, the radio user starts a transmission by pressing the PTT button.
In a transmission trunked call, when the user releases the PTT button, the central controller again receives the Disconnect tone from the radio.
The central controller immediately stops sending the LSHS and transmits a Disconnect word. When each radio receives the Disconnect word, it automatically squelches and reverts back to monitoring the control channel.
If the user wants to continue the message, or if some other user wants to respond, the channel will be lost, and the channel request and assignment process must be repeated. Therefore, Transmission Trunking is best used for calls where most calls are one-way calls.
Transmission trunking can make the most use of channel air time. However, during system busy periods, conversation continuity may be disrupted because of the immediate disconnect that occurs after each transmission.
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Each individual radio in a Motorola trunking system is uniquely identified by a:
a. Voice channel ID.b. Unit ID.c. Talkgroup ID.d. Announcement group ID.
When all of the highway crews of a Public Works department need to communicate with one another, they are assigned to a(n):
a. Fleet.b. Talkgroup.c. ISW.d. Private conversation.
True or False
Message Trunking uses a message trunked timer to give users a chance to respond after a radio is done transmitting.
__X__ True _____ False
True or False
In an announcement group call, radio users cannot talk back to the dispatcher for clarification or questions.
_____ True __X__ False
Which of the following is the brains of a Motorola trunking system, which manages and controls the entire system:
a. Central Controller.b. Base Station Repeater.c. Centralized Interconnect Terminal.
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d. None of the above.
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Module 3. Trunked Call Types
Topic 1: Talkgroup Calls 3-3This topic discusses talkgroup calls, which provide the primary level of communication in a trunked radio system.
Topic 2: Announcement Group Calls 3-4This topic describes announcement group calls, shows how announcement group calls are initiated and received, and lists announcement group call options.
Topic 3: Private Conversation II Calls 3-7This topic examines private conversation calls and describes the Private Conversation II call feature.
Topic 4: Call Alerts 3-11This topic discusses the call alert feature, which allows the dispatcher to send a paging message to an unattended radio.
Topic 5: Emergency Calls 3-12This topic describes emergency calls that radio users can employ to inform the dispatcher of situations that may need immediate attention.
Topic 6: Telephone Interconnect Calls 3-15This topic examines the telephone interconnect feature that provides radio users with access to the public switched telephone network.
Activity 3-24In this activity, you will match audio tones generated by the radio with their meanings.
Module Exercises 3-25
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This module ends with exercises that test your mastery of module objectives.
The purpose of this module is to describe the types of calls that can be made in a trunked system.
Identify the various types of calls available in a trunked system.
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Topic 1: Talkgroup Calls
The talkgroup is the primary level of communication in a trunked radio system, so the majority of conversations take place within a talkgroup. Therefore, radios assigned to a given talkgroup usually communicate only with other members of the same talkgroup. When a radio user places a talkgroup call, the transmission from that user’s radio is received by all other active radios in the same talkgroup. This provides the effect of a private channel down to the talkgroup level and prevents members of one talkgroup from hearing the talkgroup calls generated by radios in other talkgroups.
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Topic 2: Announcement Group Calls
An announcement group is a collection of talkgroups. To see how an announcement group call works, assume that talkgroups A, and B form an announcement group.
When a user places an announcement group call, the transmission from that user’s radio is heard by all the radios in all the talkgroups in that announcement group. An announcement group call allows a user to transmit a message to all the radios in two or more talkgroups simultaneously.
The advantage of announcement group calls is that critical information is received at once, by as many talkgroups as necessary. In addition, radio users can talk back to the originator of the announcement group call if necessary.
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Initiating an Announcement Group Call
Assume that the radios in talkgroup A are in the middle of a conversation
The dispatcher initiates an announcement group call for this announcement group, which consists of talkgroup A and talkgroup B.
Receiving an Announcement Group Call
Assume all the radios in talkgroups B are idle. All the radios in talkgroups B are immediately switched to the announcement group call channel and will hear the announcement group call.
In addition, those units in talkgroup A that are receiving the talkgroup A transmission are immediately switched to the announcement group call channel. Only the radio in
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talkgroup A that is transmitting at the time of the announcement group call will not be immediately switched to the announcement group call channel.
When that radio dekeys, it will join the announcement group call if it is still in progress.
Announcement Group Call Options
An announcement group call can be set to wait while talkgroups finish any calls in progress, which allows all the radios in the announcement group to hear the call. Alternatively an announcement group call can be set to interrupt existing talkgroup communications, not waiting for other transmitting radio users to stop keying their radios. Those users join the call in progress as soon as they stop pressing their PTT buttons.
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Topic 3: Private Conversation II Calls
The Private Conversation II (PC II) feature allows one radio user to talk to and be heard by only one other radio user. This feature allows a supervisor to discuss confidential matters with a particular member of a talkgroup while the radios of other members of the same talkgroup remain squelched. Radios that do not have the PC II capability installed cannot be involved in a Private Conversation call.
Individual Radios that have the Private Conversation II capability can be set up one of the following ways:
Decode Only. Receive Private Conversation II calls, but not initiate them.
Simple Encode. Initiate a Private Conversation II call to only one other radio.
Multiple Encode. Initiate a Private Conversation call to a programmed list of up to eight other radios.
Unlimited Encode. Initiate a Private Conversation call to any other radio in the system.
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Initiating a Private Conversation Call
To initiate a Private Conversation call, the user presses the Private Conversation button and then selects the radio to receive the private call. The user can do this by selecting from a pre-programmed list of radios or by keying in the Unit ID of the radio using the numeric keypad.
After the user selects the recipient of the private call, the user presses the PTT button. The initiating radio then sends two ISWs over the control channel. The first ISW contains the radio’s own Unit ID.
The second ISW contains the Unit ID of the radio being called.
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The central controller receives the ISWs, recognizes a request for Private Conversation II call, and assigns the two radios to an available voice channel. The receiving radio generates a special alert tone to notify the user of the receipt of a Private Conversation call.
Answering a Private Conversation Call
To answer the Private Conversation call, the user of the receiving radio presses the Private Conversation button.
The two radios can then converse, and no other radio in the trunked system is allowed to monitor the assigned voice channel.
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If the receiving radio has a visual display, the user can view the Unit ID of the calling party before responding to the call.
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Topic 4: Call Alerts
A dispatcher or supervisor might call a particular radio user and find that the user does not answer the call. This typically means that the radio is temporarily unattended. The dispatcher or supervisor, or other authorized user, can send a paging message, called a Call Alert message, to the unattended radio. When the unattended radio receives the Call Alert message, it automatically sends an acknowledge signal back to the originating user. The radio then activates a Call Alert indicator in the radio to alert the radio user that there is a Call Alert message waiting. The Call Alert indicators in the receiving radio may be audible or visual, depending on the capabilities of the radio. The Call Alert indicators remain active until the radio user returns to the radio and acknowledges the page. As part of the Call Alert message the radio also displays the Unit ID of the radio that originated the Call Alert message. Call Alert signaling is accomplished over the control channel and do not affect voice channel usage.
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Topic 5: Emergency Calls
Radio users can use Emergency Call capability to inform dispatchers of life-threatening situations. The transmission of the Emergency Call Alarm signal takes precedence over any other signalling activity in process in the system. Depending on how the system is configured, the Emergency Call Alarm message automatically repeats a predetermined number of times or repeats until the dispatcher acknowledges it.
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Initiating an Emergency Call
The user sends an Emergency Alarm by pressing the Emergency button on the radio.
The user can then initiate an emergency call by pressing the PTT button.
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When the user presses the Emergency button, the radio immediately transmits an Emergency Call Alarm signal over the control channel.
After the user presses the PTT button after pressing the Emergency button, the radio automatically goes into an Emergency Call mode. If all voice channels are occupied, the emergency call may be placed at the top of the Busy Queue. Alternatively the system may be set up to use a feature called Ruthless Preemption to terminate an active call and to immediately assign the emergency call to that voice channel.
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Receiving an Emergency Alarm
The dispatcher is immediately notified of the receipt of an Emergency Alarm by an audible alert tone and a visual display of the Unit ID of the emergency caller's radio.
Since the Emergency Alarm signal is sent over the control channel, the dispatcher is notified of the emergency immediately without the emergency caller having to wait for an available voice channel.
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Topic 6: Telephone Interconnect Calls
The Telephone Interconnect feature allows individual radio users to make or receive telephone calls using the radio. This feature also allows a supervisors to dispatch an entire talkgroup using an ordinary telephone. Since this feature allows an individual user to tie up one of the available voice channels, the system is normally set up to limit the number and length of telephone interconnect calls that are allowed.
In order to use the telephone interconnect option, the central controller must contain a Telephone Interconnect terminal. This device connects the telephone lines to the base station equipment.
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Types of Telephone Interconnect Calls
Three types of telephone interconnect calls can be made:
Radio to Landline Phone
To call a landline phone from a radio, a radio user presses the Telephone Interconnect button.
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The radio sends an ISW to the central controller, indicating a request for a Telephone Interconnect call. In this example, assume that only repeaters 2 and 3 have been configured to support Telephone Interconnect calls.
When the central controller receives the request, it searches for an available interconnect channel. If one is available, it is assigned to the requesting radio.
The radio user then hears a dial-tone.
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If all of the interconnect channels are active, the radio use hears a busy-tone. The central controller then queues the Telephone Interconnect call request until an interconnect channel becomes available.
When a channel becomes available, the requesting radio is assigned that voice channel, and the user hears a dial-tone.
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The user then enters the desired phone number on the keypad. The telephone call then goes through normally.
If the user is using a simplex radio, both parties must be aware that while the radio is keyed, the radio user cannot hear the land line user. To remind users of this, the telephone user hears a soft beep tone each time the radio user releases the PTT button. This indicates that the radio user can now hear the land line user.
Terminating a Telephone Interconnect Call
A telephone interconnect call can be terminated in one of three ways:
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The central controller maintains a variable timeout timer to control the duration of Telephone Interconnect calls. Fifteen seconds before the timeout expires, both parties hear a Timeout Alert tone.
The central controller terminates the Telephone Interconnect call 15 seconds after generating the Timeout Alert tone. If a radio is transmitting 15 seconds before the timer expires, the timer temporarily stops, the system is-sues the Timeout Alert after the radio is de-keyed, and the timer restarts to allow 15 seconds before the central controller disconnects the call.
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Landline Phone to Radio
To call a radio from a landline phone, a telephone user dials a phone number to connect to the radio system. If all Telephone Interconnect channels are occupied, the caller hears a busy tone. The caller must then hang up and try again later.
If a Telephone Interconnect channel is available, the Telephone Interconnect terminal accepts the call, and the telephone caller hears a Talk tone. The caller now dials an access code to indicate the radio to be connected to.
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If the receiving radio is involved in another call or radio conversation, the central controller sends a fast-ringing signal to the telephone caller.
The central controller then begins signaling the radio on the control channel. The central controller continues signaling for 20 seconds or until the central controller receives an Acknowledge tone from the radio, indicating that the radio is now free to receive the phone call.
When the radio becomes available, both the caller and the radio user hear a telephone-type ringing tone.
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The radio user answers the call by pressing the Telephone Interconnect button.
The radio then sends an ISW to the central controller. The central controller assigns a Telephone Interconnect channel to the radio, and the telephone conversation can take place.
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Landline Phone to Talkgroup
To call all the radios in a talkgroup from a landline phone, a telephone user dials a telephone number to connect to the radio system. As with a call to a single radio, if an interconnect channel is available, a tone signals the caller to enter the appropriate code for the talkgroup. The central controller then dispatches the call like any other talkgroup call by assigning a voice channel to the target talkgroup. The telephone caller’s transmission is then heard by all active radios in the talkgroup.
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Match radio tones with their meanings.
Private Conversation Alert. Generated by the radio to alert the user of a Private Conversation Call.
Call Alert. Generated by the radio when the radio receives a Call Alert message from the dispatcher.
Dial Tone. Generated by the radio when the radio user initiates a telephone interconnect call, and a telephone interconnect channel is available to handle the call.
Busy. Generated by the radio when the radio user initiates a telephone interconnect call, and no telephone interconnect channel is available to handle the call.
Timeout Alert. Generated by the radio when a telephone interconnect call is in progress and there ate 15 seconds remaining before the central controller times out and automatically terminates the call.
Phone Ring. Generated on a telephone interconnect call when a telephone use calls a radio user. Both the telephone user and the radio user hears this tone.
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Match each of the following call types with the call description that best describes it.
A The transmission from a user’s radio is heard by all the radios in two or more talkgroups.B Takes precedence over any other signalling activity in process in the system.C Permits one radio user to talk to and be heard by only one other radio user.D Used to send a paging message to an unattended radio.E The transmission from a user’s radio is received by all other active radios in the same talkgroup.F Allows radio user to make or receive telephone calls using the radio.
True or False
A radio equipped with the Private Conversation II feature can engage in a private conversation with any other radio.
_____ True __X__ False
True or False
A telephone interconnect device is required at the central site in order to handle phone calls.
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__X__ True _____ False
Which of the following ensures that critical information is received at once by as many talk groups as desired, throughout the entire system:
a. Call Alert.b. Telephone Interconnect.c. Announcement Group.d. Private Conversation II.
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Module 4. Trunked System Features
Topic 1: Trunking System Access Features 4-2This topic describes some important Motorola trunking system features relating to providing access to the trunking system.
Activity 4-4In this activity, you will match system access features with descriptions of their functions.
Topic 2: Trunking System Reliability Features 4-5This topic describes some important Motorola trunking system features relating to reliability.
Activity 4-8In this activity, you will match reliability features with descriptions of their functions.
Module Exercises 4-9This module ends with exercises that test your mastery of module objectives.
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The purpose of this module is to provide an overview of the access features available in a trunked system, how those features work, and their associated benefits. Where appropriate, the tones generated by the radio to indicate specific access conditions will be demonstrated (for example, busy tone or out of range tone). This modules covers the various system time-out parameters and how they impact system operation. It also provides an overview of the reliability features available in a trunked system, how those features work, and their associated benefits.
Describe trunked system access features. Describe the trunked system reliability features.
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Topic 1: Trunking System Access Features
The graphic below lists trunking system access features. These features are described in the following sections
The Busy tone is generated when the PTT button is pressed at a time when all voice channels are occupied.
Busy Queue/Call Back
When all voice channels are in use, call requests are put in a waiting queue and are served on a first-in-first-out (FIFO) basis. When a compatible channel becomes free, the central controller selects the oldest entry in the waiting queue and sends the associated radio a Call Back signal, consisting of a short series of beeps.
Out of Range/Out of Service
If a System Status Word (SSW) cannot be detected by the radio, this is an indication that either the radio is out of range or the trunking central controller is out of service. When the radio detects this condition, the radio generates an Out of Range tone (a continuous Busy tone) whenever the radio user presses the PTT button.
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Talk Permit (optional)
The optional Talk Permit feature causes the radio to generate a brief series of tones, identical to the Call Back tones. This provides the user with an explicit indication that the user may successfully transmit on the voice channel.
When a radio user presses the PTT button, the radio automatically sends channel requests ISWs until the request is acknowledged by the central controller or until 4 seconds (16 tries) have elapsed. This feature makes it unnecessary for the user to continually press the PTT button while trying to gain access to the trunked system. Radios transmit channel request ISWs using random timing to reduce contention on the control channel.
Recent User Priority
The term recent user refers to a talkgroup that was previously using a voice channel and then stopped transmitting on it. For 10 seconds after a talkgroup transmission ends, the recent user talkgroup has priority over other system users.
In a trunked communication system, busy periods may occur in which all repeaters in the system are occupied with voice traffic. In order to provide immediate access to the most critical services during busy periods, radios support eight levels of user priority in controlling access to system services.
Priority level 1 is reserved for Emergency Calls. The usage of priority levels 2 through 8 are determined by the System Manager. In the event the system is busy, calls are processed on a priority basis, beginning with level 1 (emergency calls) and proceeding down through priority levels 2 through 8 as voice channels become available.
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Match each of the following trunking system access features with the statement that best describes it.
Trunking System Access Features:
A. Busy Queue/Call BackB. Out of Range/Out of ServiceC. Talk Permit (optional)D. Automatic RetryE. Recent User Priority
E Provides a user who was using the voice channel with priority over new users.B Generates a busy tone when the user presses the PTT button and the radio is out of its service area or when the central controller is out of service.C Generates a series of tones when the radio user presses the PTT button and there is a voice channel available.A Permits call requests to be served on a first-in-first-out (FIFO) basis when no voice channels are available.D When the radio user presses the PTT button, the radio automatically sends channel requests ISWs until the request is acknowledged by the central controller or until a time interval has elapsed.
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Topic 2: Trunking System Reliability Features
The graphic below lists trunking system reliability features. These features are described in the following sections.
Channels are assigned as needed so users are not dependent on any given channel for communications. The failure of individual repeaters, thus making one or more channels unavailable, would not be apparent to radio users in most trunked systems.
Control Channel Switching
If the control channel fails, the trunking central controller is programmed to assign another repeater to perform the duties of the control channel. Up to four stations in a Motorola trunked system are eligible for assignment as the control channel.
The trunking central controller is programmed to detect any loss or reduction in output of individual transmitters. When the transmitter output power falls below a predetermined level, the channel is automatically made unavailable for assignment.
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Misdirected Radio Protection
This feature ensures user privacy from other users in the system. All radios in the system receive a voice channel grant and channel assignment. It is up to the radio to decide if it should be involved in the call. In the event a radio decodes a grant incorrectly and moves to the assigned voice channel, its receiver would not unmute unless it decoded another data packet which contained information particular to its own assigned talkgroup.
Continuous Assignment Updating
Once an announcement group call or talkgroup call is assigned to a voice channel, the control channel continues to transmit channel assignment information for as long as the call is using the voice channel. A radio just coming into service will receive this signal and will be sent to the appropriate voice channel to join the rest of its talkgroup. The central controller transmits channel assignment information serially on the control channel.
To ensure continued communications in the event of a major failure, the trunked system is designed to go into Failsoft mode. Major failures that will place the system into Failsoft mode are:
Failure of the central controller. Failure of all four control channels. Failure of all voice channels.
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A system will be in Failsoft mode within .3 seconds after a failure is detected. When in Failsoft mode, radios operate as they would on a conventional repeater system.
A sub-audible data word is continuously sent out by the system repeaters to let the radios know that the system is operating in Failsoft mode. Radio users are made aware that the system is in Failsoft by the automatic sounding of a low-level Alert tone every 10 seconds.
The voice channel that the radios in a particular talkgroup use for communication while the system is in Failsoft mode is programmed into the radios. Depending on how many talkgroups there are on the system and how Failsoft is set up, some talkgroup privacy may be lost.
In most cases, Failsoft channels are assigned by system. Radios with multiple system capability will have a Failsoft channel programmed for each system. The system administrator can optionally set up Failsoft by talkgroup. Each radio would then have an appropriate Failsoft channel programmed for every talkgroup with which it is associated. When the radio user changes talkgroups while in the Failsoft mode, the radio automatically switches voice channels.
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Match each of the following trunking system reliability features with the statement that best describes it.
System Reliability Features:
A. Control Channel SwitchingB. Transmitter ShutdownC. Misdirected Radio ProtectionD. Continuous Assignment Updating
D The control channel continues to transmit channel assignment information for as long as the call is using the voice channel.A Assign another repeater to perform the duties of the control channel.B When a transmitter output power falls below a predetermined level, the channel is automatically made unavailable for assignment. C Allows a radio to decide if it should be involved in the call.
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Which of the following conditions indicates that the radio is out of range of the central controller site:
a. The radio generates a Call Alert tone.b. The radio cannot detect the System Status Word (SSW) transmitted by the central controller.c. The radio does not get a response to the Call Request ISW that it transmits.d. None of the above.
The central controller function in a Motorola trunked system is performed by:
a. A special repeater that performs control channel functions only.b. Any repeater at the site of the central controller.c. One of up to four repeaters designated as eligible for assignment as the control channel. d. The dispatcher.
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Module 5. Private Trunked Systems
Topic 1: Motorola Trunking Systems 5-3This topic categorizes Motorola trunking systems as either single-site trunking systems or wide area trunking systems.
Topic 2: SMARTNET Systems 5-5This topic introduces the features and capabilities of Motorola SMARTNET trunking systems.
Topic 3: SmartWorks Systems 5-6This topic introduces the features and capabilities of Motorola SmartWorks trunking systems.
Topic 4: StartSite Systems 5-7This topic introduces the features and capabilities of Motorola StartSite trunking systems.
Topic 5: Simulcast Systems 5-10This topic introduces the features and capabilities of Motorola Simulcast trunking systems.
Topic 6: Receiver Voting Systems 5-12This topic introduces the features and capabilities of Motorola Receiver Voting trunking systems.
Topic 7: SmartZone Systems 5-13This topic introduces the features and capabilities of Motorola SmartZone trunking systems.
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Topic 8: SmartZone OmniLink Systems 5-15This topic introduces the features and capabilities of Motorola SmartZone OmniLink trunking systems.
Topic 9: Dimetra Systems 5-17This topic introduces the features and capabilities of Motorola Dimetra trunking systems.
Activity 5-19In this activity, you will match Motorola trunking systems with descriptions of their characteristics.
Module Exercises 5-20This module ends with exercises that test your mastery of module objectives.
The purpose of this module is to provide an overview of the types of trunked systems available from Motorola. Users will be able to click on a specific feature from a feature list to see a more detailed description/definition of that feature.
Describe each of the trunked systems types provided by Motorola.
Describe the Voice on Control (VOC) operation available in SmartZone systems.
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Topic 1: Motorola Trunking Systems
Single-Site Trunking Systems
Motorola's trunked systems can be divided into two groups; single-site systems, and wide area coverage systems.
Single-site trunked systems include:
SMARTNET SmartWorks StartSite
Wide Area Trunking Systems
Motorola offers the following types of trunked wide area system configurations. These are:
The first topics in this module describe the Motorola trunking systems that support a single site. After that, additional topics describe Motorola wide area trunking systems.
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Topic 2: SMARTNET Systems
SMARTNET is Motorola's most feature packed single-site trunking system. SMARTNET is designed to provide flexible talkgroup partitioning for those customers who may need to expand talkgroup sizes. SMARTNET supports up to 28 channels.
SMARTNET has the following capabilities:
Flexible talkgroup partitioning allows customers to expand talkgroup sizes
48,000 Unit IDs 4,000 talkgroups
Up to 28 channels Up to 8 priority levels Automatic Unit ID Reduced access time (250 ms for single-site systems) Priority Scan Private Conversation Call Alert Emergency Call/Alarm CentraCom Consoles
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Topic 3: SmartWorks Systems
SmartWorks is a single-site trunking system that can support up to seven channels.
SmartWorks has the following capabilities:
Designed for small system users Expandable to supports from 3 to 7 channels 700 radios or less
Provides Single Site Coverage Based on SMARTNET II technology Can support Type I, Type II, or hybrid operation Has many trunking advanced features Less costly than full featured trunking systems Telephone Interconnect Console Interface for Control Center Dispatching Supports SECURENET encryption subsystems at 800
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Topic 4: StartSite Systems
StartSite supports from one to five voice channels and is an economical, entry-level trunking system geared to single-site users. As with any Motorola trunked system, the central controller plays a key role in controlling the operation of the trunking system.
All StartSite systems include the following standard trunking features:
Fast Failsoft Base Station Identification Both Major and Minor Local Alarm Functions Channel Activity Reporting System Manager Terminal Access
The system manager can enter a command to switch the central controller between dynamic control channel mode and active control channel mode. The following control channel features are available only when the central controller is operating in the active control channel mode of operation.
Radio Inhibit Dynamic Regrouping Continuous Assignment Updating Busy Queuing and Callback Recent User Priority Talkgroup, Announcement Group, and System Calls
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Priority Level Control Private Call and Call Alert Unit Registration and Talkgroup Affiliation
StartSite Control Channel Features
Two StartSite central controller configurations are available:
Continuous Control Channel Selectable Control Channel
Continuous Control Channel
With the continuous control channel configuration of the StartSite central controller, the central controller operates in the same mode as the central controller in other Motorola trunked systems. With a continuous control channel, one of the repeaters always functions as the control channel. While a repeater is performing the duties of the control channel, it cannot be used for voice communications.
Selectable Control Channel
The selectable control channel configuration of StartSite central controller offers two switchable modes of operation:
Active control channel mode Dynamic control channel mode
Active Control Channel Mode
When the selectable control channel is operating in active control channel mode, the central controller operates in the same manner as a central controller operating with a continuous control channel. In this mode, one of the repeaters is chosen to perform the duties of the control channel, and that repeater is not available for use as a voice channel.
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Dynamic Control Channel Mode
When the central controller is operating in dynamic control channel mode, the system can use all the repeaters to support voice channels without dedicating one of the repeaters for full-time use as the control channel. This results in more subscriber air time and full use of all channels for voice communications, an important benefit in a smaller system supporting one three or five channels.
When the dynamic control channel is assigned to support voice communication, the following occurs:
All existing calls remain active. Any new call requests are considered out of range. No control channel processing can occur.
When any existing call on an dynamic control channel ends, the dynamic control channel becomes available for use as a control channel in less than one second.
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Topic 5: Simulcast Systems
A Simulcast system supports the simultaneous transmission of identical carrier signals from multiple, geographically separated transmitter sites. A single-site trunked system is centralized in structure, with all of the repeaters installed at a single site. However, a Simulcast system allows the repeaters to be located at different sites. Up to eleven sites can be accommodated in a Simulcast system. This provides a much larger coverage area.
In a Simulcast system, when a radio user presses the PTT button, the radio signal is received by the control channel, and the voice signal is then retransmitted by repeaters at each of the other sites simultaneously.
One site, which contains a central controller, is designated as the prime site. It is here that all the channel designation decisions are made. The other sites are called remote sites and contain a remote controller instead of a central controller. The remote sites are extensions of the prime site, and follow orders from it.
With a Simulcast system, each site must contain identical repeater configurations. The remote sites must also be linked to the prime site to coordinate audio and data transfers.
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In simulcast systems there are overlap areas between the sites where the same audio information from two or more transmitters on the same frequency may be received by a radio. For good audio performance it is imperative that the transmitters be exactly in-phase with each other. Otherwise, noise or distortion may be experienced.
Simulcast is very effective in expanding the transmission of a trunked radio system, and provides fill-in where buildings or mountains may cause shadow coverage.
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Topic 6: Receiver Voting Systems
Receiver voting is an alternative which extends the talk-in capabilities of a system. It involves placing additional receiver sites in areas around the associated transmitter site, where talk-back coverage is weak.
Through the use of voting comparators, the best received audio signal is voted and passed on through the audio network for transmission. Receiver voting systems are the recommended wide area alternative in frequency congested areas where talk-in capability needs to be expanded.
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Topic 7: SmartZone Systems
SmartZone is a high capacity, integrated wide area coverage radio/data system. Although SmartZone is primarily for use with trunking technology, it can also integrate conventional sites and systems. Larger geographic areas can be covered with a SmartZone system. A single zone of a SmartZone system can have up to 48 subsystems.
Because SmartZone can incorporate frequency efficient simulcast subsystems, and frequency re-use systems, frequency availability can be accommodated for every segment of a user's operations.
SmartZone's multiple subsystem design also uses a variable number of repeaters at each of the sites to handle different traffic loading requirements. A low traffic area has fewer repeaters than an area with a high volume of traffic.
SmartZone systems are available in the following subsystems:
Standalone sites with 6809 controllers Standalone sites with IntelliRepeaters Receiver Voting with 6809 controllers Simulcast with 6809 controllers
SmartZone channels can be configured for digital (ASTRO) and/or analog operation. Each channel is programmable for digital only, mixed analog and digital, or analog only operation.
A SmartZone system configuration is comprised of a Master Site and Remote Sites. Remote sites can be considered as building blocks to the SmartZone system's functionality. They are very similar to standard SMARTNET II systems, however they are modified to behave and be an integral part of the SmartZone network.
SmartZone Voice On Control
Voice on Control is used at a low density SmartZone site which contains four or less repeaters. Sites with a 6809 central controller cannot support this feature. A repeater
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site with Voice On Control (VOC) software allows the control channel to be temporarily used for voice communication. This helps increase capacity when all voice channels at the site are in use.
When a radio requests a channel and all voice channels are in use, a channel grant is sent out on the control channel along with a code telling other radios that a control channel is unavailable. If another radio requests a channel, it receives a busy tone. When the repeater designated as the control channel is no longer needed for voice traffic, it returns to service as the control channel.
For proper operation, radios and other equipment must be equipped with Voice on Control software. Voice on Control operation is best applied for low traffic, fill-in coverage for remote locations which only require the basic trunking features and wide area coverage with other sites.
The following are capabilities available with Voice on Control operation:
Talkgroup calls Emergency calls Interconnect calls subject to limitations noted below Secure calls subject to limitations noted below Enhanced Private calls (not available at 800 MHz) Internal queuing of requests by VOC equipped radios Subscriber access control with 10 priority levels Dynamic Regrouping when the control channel is
available Selective Radio Inhibit when the control channel is
available Call alerts when the control channel is available
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Topic 8: SmartZone OmniLink Systems
SmartZone OmniLink is a software-based, very wide area radio communications network based upon the interconnection of multiple SmartZone systems. A SmartZone OmniLink system operates with virtually transparent boundaries, creating homogeneous system operation over very large geographical areas. SmartZone OmniLink carries over the majority of SmartZone features, while providing additional features and enhancements specific to the needs of a very wide area radio network.
SmartZone OmniLink supports the interconnection of up to four SmartZone systems with 32 Zone Controller ports per zone for a total of 128 ports for a system. Each SmartZone OmniLink zone also contains an Embassy Audio switch, offering a substantial expansion of the audio switch capacity due to multiple audio switches in the system.
SmartZone OmniLink supports the same system addressing as SmartZone:
A maximum of 48,000 unique individual IDs A maximum of 4,000 unique talkgroup IDs A maximum of 2,000 unique talkgroup Ids with Priority
Site IDs need to be unique within a zone, but not between zones. The SmartZone OmniLink Zone (system) IDs must be unique.
SmartZone OmniLink is Project 25 Common Air Interface (CAI) compliant and supports the following modulation modes:
Clear Analog ASTRO digital (IMBE vocoding only, does not support
VSELP) Mixed mode Analog/ASTRO Encrypted ASTRO digital or 12 Kb SECURENET (12 KB
SECURENET and ASTRO digital are not supported on the same system)
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SmartZone OmniLink is Frequency Band independent and allows intermixing the following frequency bands at the Zone level:
900 MHz 800 MHz UHF band VHF band
SmartZone OmniLink supports the following types of call across all zones:
Talkgroup Calls Announcement Group Calls Telephone Interconnect Calls
Landline to radio — Find unit anywhere Radio to landline
Emergency Call and Alarm Call Alert
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Topic 9: Dimetra Systems
This overview is intended to give the reader a basic understanding of Motorola’s TETRA compliant radio system, Dimetra™ (DIgital Motorola European Trunked Radio).
The Trans European Trunked RAdio (TETRA) standard is a common European standard for advanced digital trunked radio networks. The standardization work is carried out by the European Telecommunications Standards Institute (ETSI).
The Motorola Dimetra system family is a highly sophisticated range of digital radio equipment that delivers the full benefits of the TETRA standard designed to meet the needs of users of both private mobile radio networks (PMR) and public access mobile radio (PAMR) systems.
The development of the Dimetra system was based on Motorola’s experience in technologically proven systems such as SmartZone and iDEN. This addition to Motorola’s portfolio of radio systems includes a comprehensive product line-up including base stations, switches, operations management control, portables, mobiles, and consoles. All of these have the ability to be simply and easily reprogrammed whenever there is a system enhancement, or to meet future requirements as the new technology evolves.
Dimetra provides one Master Site and multiple Remote Sites, known as a Dimetra Zone.
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The figure illustrates a Dimetra system with one Master Site and a number of Remote Sites, i.e. one Zone, also known as Switching and Management Infrastructure (SwMI).
The Master site implements the following main functions:
System Management. HP Unix work station based network containing System Databases and providing intuitive Graphical User Inter-face (GUI) for configuring the system and the radio subscribers.
Group Switch Controller. Provides very fast call control for group communication in a wide-area network. The Group Switch Controller also controls private calls, interconnect calls and circuit data calls as well as providing mobility information for other communication types such as Short Data Service.
Group Switch. High speed digital switch, which is specifically designed for wide-area systems with console dispatchers. Among the functions of the Group Switch are the capability to route any bit pat-tern to one or multiple destinations, which is a unique requirement in wide area group communication systems.
Dispatch Consoles. Highly advanced dispatch system which provides fixed dispatch capabilities to both the Dimetra trunked system as well as conventional PMR radio systems including the ability to connect calls between these systems. The dispatcher may also connect calls to a telephone system.
Telephone Gateway. Computer Telephony based Telephone Gateway providing easy adaptation of current and new analogue and digital line interfaces.
Transcoder. Converts audio streams between TETRA ACELP compressed voice and 64 Kbps PCM voice. Pulse Code Modulation voice is used for the Dispatch Consoles and the Telephone Gateway.
Site Link Multiplexer. Provides efficient usage of site link capacity, i.e. routing all relevant data such as ACELP voice, TETRA data, Call Control and Site Management via one link.
The Remote Sites, also known as Enhanced Base Transceiver System (EBTS) contain the following main functions:
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Base Radio (BR). Each BR provides one TETRA carrier, i.e. four TETRA time slots. The BR is optionally equipped with three receivers for diversity reception which increases the coverage area and reception quality.
Site Controller: Controls up to 7 BRs and provides the interface to the Master Site. In case of site link failure the site controller provides local trunking capabilities for continued communication within the site coverage area.
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Match Motorola trunking systems with descriptions of their characteristics.
Motorola Trunking Systems:
A. SMARTNETB. SmartWorksC. SimulcastD. SmartZoneE. SmartZone OmniLink
Trunking System Descriptions:
D Multiple-site trunking system that uses a variable number of repeaters at each site, can contain up to 48 subsystems, and comprises a Master Site and one or more Remote Sites.B Single-site trunking system, available in both 800 and 900 MHz versions. that supports up to seven channels. C Multiple-site trunking system that supports the simultaneous transmission of identical carrier signals from multiple, geographically separated transmitter sites.A Single site trunking system that provides flexible talkgroup partitioning, unrestricted roaming capability, and supports up to 28 channels.E Multiple-site trunking system that uses software techniques to provide radio coverage over a very large geographical area that may be divided into multiple zones.
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Which of the following single-site trunking systems is Motorola's most powerful, supporting up to 28 voice channels:
a. SmartWorksb. SMARTNETc. StartSited. SmartZone
Which of the following wide-area trunking systems supports a single zone that can have up to 48 subsystems:
a. SmartZone OmniLinkb. Receiver Votingc. SmartZoned. Simulcast
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Module 6. Trunking Signaling
Topic 1: Signaling Sequence 6-3This topic illustrates the sequence in which signaling takes place within a Motorola trunking system during call processing.
Activity 6-15In this activity, you will place descriptions of signals into the sequence in which the signals flow during normal call processing.
Topic 2: Failsoft Signaling 6-16This topic describes the signaling that takes place within a Motorola trunking system when failures in the central controller occur.
Topic 3: System Timeouts 6-17This topic examines the various system timeout parameters that control the operation of various aspects of the trunking system.
Module Exercises 6-18This module ends with exercises that test your mastery of module objectives.
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The purpose of this module is to provide technicians with a detailed explanation of signaling words and tones and how they are used in a Motorola trunking system. This knowledge is important when troubleshooting system access problems in a trunked system.
Describe the various types of signaling used in a trunked system and how signaling words and tones are used in processing a call.
Describe the timeout parameters used in a trunked system.
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Topic 1: Signaling Sequence
This topic describes the inbound and outbound signals used by the central controller in a trunked system to manage the system resources and control access to the system. The following pages show how signals flow through a Motorola trunking system during the processing of a call.
Step 1 — System Status Word/System ID OSW
System Status Word/Word Frame
The System Status Word (SSW) is transmitted by the central controller through the control channel. The SSW is received by all the radios listening to the control channel and is transmitted in a format called a Word Frame.
The Word Frame carrying the SSW occupies a 23.3 ms time frame and is sent continuously at 3600 baud. It is transmitted only when the system is idle and is used to synchronize the subscribers to the control channel. The Word Frame tells the radio that this is a Motorola system. The Word Frame is used for bit synchronization only and provides no useful information to the user.
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System ID OSW
The System ID OSW is inserted serially after an SSW at least once every three seconds and contains system identification and control channel information.
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Step 2 — Inbound Signal Word (ISW)
When a radio user presses the PTT button is pressed, the radio sends an Inbound Signal Word (ISW), sometimes called a Channel Request, to the central controller via the control channel.
The radio sends the ISW to the central controller at 3600 baud in 23.3 ms word frames and is transmitted in synchronization with the central controller's SSW. ISW transmission is synchronized to the central controller's SSW.
The information bits in the ISW contains the Unit ID, call type, and other parameters. If the radio is already affiliated with the central controller, the radio transmits a Single Word ISW containing 78 bits sent at 3600 bps (21.67 ms) with 21 information bits and 57 error correction bits.
If the radio is not yet affiliated with the central controller, it transmits a Dual Word ISW.
The format of the dual word ISW is as follows:
1. First words2. First word.
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Unit ID Type of call, group or individual. Code word indicating the presence of the second word.
3. Second word Talkgroup ID. Call type description: Private Call, Call Alert, etc.
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Step 3 — Channel Grant/Busy OSW
In step 3, the central controller transmits the Channel Grant or Busy OSW.
The Channel Grant OSW contains announcement group, talkgroup, Unit ID, and voice channel assignment or status information.
The channel grant signal contains 84 bits sent at 3600 baud (23.3 milliseconds) with 27 information bits, 8 sync bits, and 49 error correction bits. The 27 information bits consist of 16 address bits, one call-type bit, and 10 status or channel bits. If the channel is in the 0 - 759 block, then the status bits contain the channel number, but if the channel is in the 760 - 1024 block, then the status word is sent in hexadecimal code.
This OSW is used to send the voice channel assignments. It consists of two consecutive words sent four times in succession. Each word contains 84 bits and is sent at 3600 bps (23.3 ms). The information bits are split into 27 information bits, 8 synchronization bits, and 49 error correction bits.
If a channel is not available (the entire system is busy) the initiating radio displays a busy light and/or produces a Busy tone.
The Channel Busy OSW has the same format as the Channel Grant except that the information causes the radios to generate a busy tone to indicate to the radio user that all repeaters are busy.
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Step 4 — Low Speed Hand Shake (LSHS)
The central controller transmits a Low Speed Handshake (LSHS) signal, also called a Connect Word. The LSHS unmutes received audio and holds receiving radios on the assigned voice channel. The LSHS is sent through the voice channel at 150 Baud. The signal consists of the first 11 bits of the talkgroup identification. If a radios does not receive or decode the LSHS, it returns to the control channel.
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When the microphone is unmuted and voice transmission begins, the radio transmits a Connect tone, which causes the central controller to keep the channel connected. The Connect tone is a sub audible tone sent by the radio on the voice channel along with voice information. The central controller checks its presence to verify that the radio is still using the voice channel. If the tone is not there, the central controller takes control of the repeater and makes it available for reassignment as a voice channel. The default frequency for the Connect Tone is 105.88 Hz. Other Connect tone frequencies are sometimes used.
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Step 5 — Disconnect Tone
In Step 5, the initiating user stops talking and releases the PTT button.
When the PTT button is released the radio does not dekey. Instead, it sends 200 milliseconds of Disconnect tone. The Disconnect tone is used to notify the central controller that the user has finished a transmission. The Disconnect tone is a 163.64 Hz. signal that is transmitted over the voice channel for 200 milliseconds. In message trunking, the central controller detects the Disconnect tone and begins a message timeout timer (max. 6 seconds, factory default set for 1 second).
If the talkgroup is programmed for Message Trunking, the central controller starts a timer at that point. If it detects no PTT from any of the radios in that talkgroup, within the allotted time, it takes control of the voice channel and makes it available to other users.
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Once a radio transmits the Disconnect Tone, the radio switches to receive mode and unmutes after detecting the LSHS.
If any talkgroup member decides to respond to the message prior to the expiration of the message timer, the conversation will continue with the new radio providing the Connect Tone.
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Step 6 — Call Continuation
In step 6, the receiving radio transmits.
Assuming that message trunking is in operation, once a radio has sent an end of transmission signal, any radio in the same talkgroup can respond to the original transmitting radio by pressing PTT and talking. When the radio user presses the PTT button, the radio sends a Connect tone, together with voice information.
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Step 6 — Call Continuation
The central controller detects the Connect tone, resets the message timeout timer, and transmits an LSHS signal so the conversation can continue.
Step 7 — Disconnect Tone
Step 7 begins when the radio user releases the PTT button
When the PTT button is released, the radio does not dekey. Instead, it sends 200 milliseconds of Disconnect tone.
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In message trunking, the central controller detects the Disconnect tone, transmits the LSHS signal via the voice channel, and begins a new message timeout timer, as before.
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Step 8 — Disconnect Word
In Step 8, the final step in this sequence, the central controller transmits.
If the central controller does not receive a Connect word before the message timeout timer expires, the central controller transmits a 125 ms. Disconnect word at 300 baud via the voice channel. When a radio receives the Disconnect word, the radio mutes and returns to control channel. The central controller then makes the voice channel available for reassignment.
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Enter numbers to the left of each of the following signaling steps to place the signals into the sequence in which they flow during normal call processing.
2 When a radio user presses the PTT button, the radio sends an Inbound Signal Word (ISW), or Channel Request, to the central controller via the control channel.3 The central controller transmits a Channel Grant OSW over the control channel.1 The central controller uses the control channel to transmit the System Status Word signal with System ID OSW signals inserted at least once every three seconds.5 When the PTT button is released the radio a Disconnect tone to notify the central controller that the user has finished a transmission. The radio then switches to receive mode and unmutes after detecting the LSHS.4 The central controller transmits a Low Speed Handshake (LSHS) signal to unmute received audio and to hold receiving radios on the assigned voice channel. The radio then transmits a Connect tone, which causes the central controller to keep the channel connected.
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Topic 2: Failsoft Signaling
During normal system operation, the central controller supplies the base station's Failsoft circuit with a Transmit Data (TDATA) signal. The TDATA signal consists of an OSW, followed by an LSHS signal, followed by a Disconnect Word signal. The TDATA signal keeps the base stations in the trunking mode. If TDATA transmission stops because of failure of the central controller, the base stations revert to the failsoft mode.
The base station unmutes and transmits a Failsoft data word.
Radios respond to the Failsoft data word and unmute, allowing service to continue via community repeater type operation.
The base station sends out a 900 Hz tone for 280 milliseconds every 10 seconds to alert the radio user that the system is in Failsoft mode.
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Topic 3: System Timeouts
The central controller maintains a set of system timeout parameters. The system manager can change these system parameters to control the operation of the system.
Major system timeout parameters are listed in the graphic below. These parameters are described in the following sections.
Carrier Timeout Period
This determines the time period for which an assigned voice channel remains unmuted and active, receiving only carrier and no handshake Connect Tone. The time can be activated after a Disconnect tone is detected by the central controller.
Fade Timeout Period
This determines the time period for which an assigned voice channel remains active after the disappearance of the Connect tone and carrier. After the timer expires, the channel is unassigned. The timer is activated after the central controller fails to detect the Disconnect tone after loss of the low speed Connect Tone.
Message Trunk Timeout Period
This determines the time period for which a voice channel remains active after receiving a Disconnect tone from a radio. After the timeout the channel is unassigned.
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Carrier Malfunction Timeout Period
This determines how long an interfering signal must be present on an unassigned channel before it is removed from system use. An entry of 254 seconds disables the time out.
The System Status Word is transmitted by:
a. The initiating radio.b. The receiving radio.c. The repeater for the active voice channel.d. The central controller.
The Disconnect tone is transmitted by:
a. The initiating radio.b. The receiving radio.c. The repeater for the active voice channel.d. The central controller.
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Module 7. Type I vs. Type II Trunking
Topic 1: Type I Trunking 7-2This topic introduces Type I trunking systems that group radios by fleet and subfleet.
Topic 2: Type II Trunking 7-3This topic introduces Type II trunking systems that group radios by talkgroup and announcement group.
Topic 3: Hybrid (Type IIi) Trunking 7-4This topic introduces Motorola trunking systems that can handle both Type I and Type II addressing.
Module Exercises 7-5This module ends with exercises that test your mastery of module objectives.
Trunking system features rely on the unique digital addresses assigned to every radio in the system. With the development of Motorola trunked systems, two addressing schemes, or protocols, have evolved: Type I and Type II.
The purpose of this module is to provide technicians with an explanation of the two types of addressing signaling words, how those signaling words are structured, when they are used, and how Type I and Type II radios can operate in the same system.
Differentiate between Type I and Type II trunking.
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Topic 1: Type I Trunking
Motorola's first trunking systems, introduced in 1977, used a protocol for assigning digital addresses to radios. This original protocol, which later became known as Type I, divides the system into groups called fleets. Each fleet is further divided into smaller groups called subfleets.
With Type I addressing, each radio is assigned a unique digital address that identifies it as a member of a particular fleet. Using this address, the radio can make group calls in any of the subfleets affiliated with its assigned fleet.
Each radio is assigned to a fleet and has a unique ID within that fleet. To address a particular radio, the central controller must indicate the radio's fleet number and unique ID within the fleet. Together, a fleet number and ID give a radio a unique digital address within the system.
Fleets and subfleets are the two levels of groups in Type I systems. The maximum number of subfleets and radio IDs a fleet can contain is fixed, though the maximum varies between trunking systems.
For Type I radios, subfleet calls are more common than fleetwide calls. A subfleet call is heard only by radios in the same subfleet. A fleetwide call is heard by all radios in the fleet.
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Topic 2: Type II Trunking
Beginning in 1987, to add more features such as capacity for more radio and group IDs, Motorola developed a new trunking protocol, called Type II. Type II trunking is the standard protocol on Motorola trunking systems.
With Type II trunking, a radio's Unit ID does not identify any particular group, so Unit IDs and group IDs can be assigned independently. With Type II trunking, any number of radios can be assigned to a group, whereas Type I trunking limits the number of radios that can be in any particular fleet.
In Type II systems, the two main levels of groups are talkgroups and announcement groups, also called multigroups. Announcement groups are comparable to fleets, and talkgroups are similar to subfleets. Announcement groups are groupings of talkgroups, just as fleets may be considered groupings of subfleets.
For Type II radios, talkgroup calls are more common than announcement group calls. A talkgroup call is heard only by radios in the talkgroup. An announcement group call is heard by all radios monitoring talkgroups within the announcement group.
With Type II systems there are no restrictions on talkgroup and individual ID combinations up to a limit of 48,000 total Unit ID values and 4,000 total talkgroups per system.
Older trunked systems support Type I signalling only. Newer trunked systems support both Type I and Type II signalling.
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Topic 3: Hybrid (Type IIi) Trunking
Several Motorola trunking systems incorporate both types of trunking signalling (Type I and Type II). These are referred to as Hybrid or Type IIi systems. Radio units with Type I and Type II capabilities are often referred to as twin type radios.
This means that a customer with an older trunking system, who may want to upgrade to a newer system at a later date, can use twin type radios in a system and not have to worry about obsolescence when upgrading at a later date.
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Which of the following identifies fleet and subfleet directly in Unit ID values:
a. Only Type I trunking.b. Only Type II trunking.c. Type I and Type IIi trunking.d. Type II and Type IIi trunking.
Which of the following allows for a maximum of 48,000 Unit IDs and 4,000 talkgroups:
a. Only Type I trunking.b. Only Type II trunking.c. Type I and Type IIi trunking.d. Type II and Type IIi trunking.
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Module 8. System ID Structure
Topic 1: System IDs 8-2This topic summarizes the types of system IDs important in Motorola trunked systems.
Topic 2: Unit IDs 8-3This topic examines the structure of the individual Unit IDs that make up the unique digital addresses assigned to the radios in a Motorola trunking system.
Topic 3: Talkgroup IDs 8-4This topic looks at the structure of the talkgroup IDs that uniquely identify each talkgroup in a trunking system.
Topic 4: Announcement Group IDs 8-5This topic discusses the structure of the announcement group IDs that uniquely identify each announcement group in a trunking system.
Topic 5: Radio Programming 8-6This topic describes the way in which a radio's talkgroup affiliation is established.
Module Exercises 8-7This module ends with exercises that test your mastery of module objectives.
The purpose of this module is to provide technicians with an explanation of the two types of signaling words, how those words are structured, when they are used, and how Type I and Type II radios can operate in the same system.
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Describe the ID structure used in a Motorola trunking system.
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Topic 1: System IDs
There are three types of system IDs important in trunking systems:
Individual Unit IDs Talkgroup IDs Announcement Group IDs
In most trunking systems, only 16,000 individual Unit IDs and 1,000 talkgroup IDs are available unless the extended (128 Mb) memory board option has been added to the central controller. Assuming the boards are purchased, the maximum number of Unit IDs increase to 48,000, and the maximum number of talkgroups increases to 4,094.
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Topic 2: Unit IDs
Each radio has only one Unit ID per system. This makes it easier to locate radios for private calls such as call alert, private conversation, and telephone interconnect.
A unique 4 digit hex number is assigned to each user on a system. The ID which is normally used is the equivalent decimal value of the hex number with the number 7 added as a prefix. The following example shows how to find the equivalent decimal Unit ID for a hex Unit ID (Example: 4B6A):
The decimal equivalent of 4B6A hex is 4*163
+11*162+6*16 +10=19306 (A and B are equivalent to 10 and 11 in the hex number system, respectively.)
Adding the prefix number (7), the decimal Unit ID is 719306.
The user has only one Unit ID per system. This makes it easier to locate individuals for private type calls, such as call alert, private conversation, and interconnect. The decimal conversion of this ID is the land to mobile ID for interconnect calls. There are up to 64,000 Unit ID's on a system of which 48,000 Unit IDs can be used.
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Topic 3: Talkgroup IDs
A talkgroup ID is a 3 digit (hex) number that represents a group of users on the system.
Any number of units can be assigned to a talkgroup. The number of talkgroups the radio may be
programmed to operate in depends on the number of trunked modes available in the radio.
The radio's programming defines the talkgroups it may operate in.
A unique 3 digit (hex) number represents a group of users on a system. The ID which is normally used is the equivalent decimal value of the hex number with the number 80 added as a prefix. The following example shows how to find the decimal Talkgroup ID for hex Talkgroup ID 8A7:
The decimal equivalent of 8A7 hex is 8*162 +10*16 +7=2215
Adding the prefix number (80), the decimal Talkgroup ID is 802215
Any number of units can be assigned to a talkgroup. The number of talkgroups the radio may be programmed to operate in depends on the number of trunked modes available.
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Topic 4: Announcement Group IDs
A unique 3 digit (hex) number represents a set of talkgroups on a system. The ID which is normally used is the equivalent decimal value of the hex number with the number 80 added as a prefix. The group may contain any number of talkgroups. The organizational needs of the customers will determine what talkgroups are affiliated with an announcement group. This information will be programmed into the system manager terminal and radios to determine which groups they will operate in.
The central controller has no preprogrammed records of announcement group to talkgroup affiliation. This data must be entered manually into the central controller using the system manager's terminal for proper call processing to take place.
An announcement ID is a unique 3 digit (hex) number that represents a collection of talkgroups in a system.
The group may contain any number of talkgroups. The organizational needs of the customers will determine what talkgroups are affiliated with an announcement group. This information will be programmed into the radios to determine which groups they will operate in.
This data must be entered manually into the central controller using the system managers terminal for proper call processing to take place.
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Topic 5: Radio Programming
The central controller does not determine the talkgroup the unit may operate in, this is done in the programming of the radio. The radio informs the central controller of the current talkgroup it is operating in using a procedure called affiliation. The Affiliation procedure can be performed by two methods, depending on how the radio was programmed to Affiliate:
Push-to-talk (PTT): The user chooses a different talkgroup on the radio. When the radio is keyed it transmits a dual-word ISW. The first word contains the Individual Unit ID and call type, the second word contains the updated talkgroup ID.
Automatic: The user changes the talkgroup selector position. A few seconds after the change, the radio automatically transmits an ISW to update the central controller of the new talkgroup ID. This gives a faster access time. The radio will use PTT affiliation if the user presses the PTT button prior to the timeout set to transmit the new affiliation information.
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A Unit ID value consists of:
a. A three-digit decimal value.b. A three-digit hexadecimal value.c. A six-digit decimal value.d. A six-digit hexadecimal value.
Which of the following uniquely identifies an individual radio in a Motorola trunking system:
a. Unit ID value.b. Unit ID value and talkgroup ID value.c. Unit ID value, talkgroup ID value, and announcement group ID value.d. None of the above.