Overhead Lines &Telephony

INDEXOVERHEAD LINES & TELEPHONY

SERIAL NUMBER

TOPICPAGE

NUMBER

1 EVOLUTION OF TELECOM 2 to10

2ERECTION OF SUBSCRIBER LOOP FROM DP POINT TO SUBSCRIBER PREMISES 11 to 21

3PROTECTIVE ARRANGEMENTS & TERMINATION OF EXCHANGE LINE AT SUBSCRIBER PREMISES 22 to 26

4 TELEPHONE INSTRUMENTS 27 to 48

RTTC, NAGPUR Page 1 of 50

CHAPTER 1

EVOLUTION OF TELECOM

First stepsThe telephone was discovered almost by accident. What people thought they were looking for was a way to make the telegraph work faster and more profitably - by sending distinct musical notes or tones simultaneously along the wires with a separate message sent on each frequency.

But they soon realized it could also include the human voice - a speaking telegraph. And if you could talk down a wire, wouldn't that be an entirely new and better way of communicating?

The individual parts of the telephone were discovered and developed by different people at different times.

Someone needed to take all those connections and draw them together into one working instrument. In the end that someone was Alexander Graham Bell - but he only just won the race.

Reis's telephone (1860) : the diaphragm manWho really invented the telephone? There are quite a few candidates, and the leading one is a German science teacher called Philipp Reis.Reis began work on the telephone in 1860, inspired by an 1854 paper by a French investigator named Bourseul, who suggested:'Speak against one diaphragm and let each vibration 'make or break' the electric contact. The electric pulsations thereby produced will set the other diaphragm working, and [it then reproduces] the transmitted sound.'His idea was a little shaky. To send sound, the transmitter diaphragm shouldn't completely make or break an electrical contact but instead should vary the current of electricity flowing. His transmitter was a make-and-break device but Reis's receiver (earpiece) used a vibrating rod (a knitting needle in fact) that was magnetized to varying degrees by an electric coil.Reis was let down by his apparatus - it could reproduce continuous musical notes well but produced indistinct speech. His telephone was shown in demonstrations all over Europe, including one in Scotland while Alexander Graham Bell was there, visiting his father.

Gray's telephone (1876)

Elisha Gray knew that all too well. On February 14, 1876, the day that Alexander Graham Bell applied for a patent for his version of the telephone, Elisha Gray applied for a caveat - a document indicating that he intended to file his own patent claim within three months.


http://www.connected-earth.com/Galleries/Pioneersandpersonalities/G/Gray/index.htm

http://www.connected-earth.com/Galleries/Pioneersandpersonalities/R/Reis/index.htm

But Gray was a few hours too late - Bell had already filed an actual patent application - and the courts later ruled that this took precedence. Even so, Gray's claim has its merits - Bell first transmitted the sound of a human voice over a wire, using a liquid transmitter of the microphone type previously developed by Gray and unlike any described in Bell's previous patent applications. He also used an electromagnetic metal-diaphragm receiver of the kind built and used publicly by Gray several months earlier.

The first telephonic sound (1875) : that elusive twangOne summer afternoon, as Bell was working in his workshop in Boston, he heard an almost inaudible twanging sound from his prototype telephone - a sort of crude harmonica with a clock-spring reed, a magnet and a wire. This was connected to a similar device in another room where his assistant Thomas Watson was working. Watson had snapped the reed on one of the instruments and from the other device Bell had heard exactly the same sound. It was the first time in the history of the world that a complex sound had been carried along a wire, and reproduced perfectly at the other end.

The first telephone call (1876) : "Mr. Watson, come here, I want you"

After hearing their telephone first transmit a sound in June 1875, Bell and Watson spent the next 40 weeks making their telephone actually speak. Finally, on March 10, 1876, Watson heard Bell's voice distinctly in the receiver saying: "Mr Watson, come here, I want you."Watson, who was in another room, dropped the receiver and rushed with wild joy across the hall to tell the glad tidings to Bell. "I can hear you!" he shouted breathlessly. "I can hear the WORDS."America's telegraph companies saw right away that Bell's telephone posed a powerful threat to their businesses and they tried to fight back. The Western Union company called on Thomas Alva Edison to develop an alternative to Bell's invention. The American Speaking Telephone Company in New York (a Western Union subsidiary) then went head-to-head with The Bell Telephone Company of Boston. Within months, Bell sued Western Union for infringement of his patents. Western Union argued that it was Elisha Gray who had invented the telephone - but lost the court battle and had to hand over Edison's telephone rights and withdraw from the telephone business.The Bell company absorbed the American Speaking Telephone Company and re-emerged as the American Bell Telephone Company in April 1880.

The first telephones arrive in Britain (1877) : 'greatest by far of all the marvels'

Sir William Thomson (later Lord Kelvin) exhibited Bell's primitive telephone before the British Association for the Advancement of Science assembly at Glasgow in September 1876, describing it as "the greatest by far of all the marvels of the electric telegraph".The first pair of practical telephones seen in Great Britain arrived in July 1877, brought here by William Preece, Chief


Electrician of the Post Office. A few months later, Bell's 'perfected' type of telephone was exhibited at another meeting of the British Association in Plymouth.

Bell forms his company (1877) : but sales are slow ...Within a year of making the first telephone call, Bell and his financial backers - Thomas Sanders and Gardiner G Hubbard - had formed the Bell Telephone Company in the United States. Unsurprisingly, early demand for the telephone was not great and prior to forming their company Bell and his partners had struggled in their attempts to promote the new invention. At one point they even offered to sell the Bell patents to the Western Union Telegraph Company - Elisha Gray's employers - for $100,000. The offer was spurned - a decision the Western Union was soon to regret bitterly.

First British long distance calls (1878) : a royal introductionAlexander Graham Bell demonstrated his telephone to Queen Victoria on January 14, 1878, at Osborne House on the Isle of Wight. During the demonstration Bell made calls to London, Cowes and Southampton. These were the first publicly witnessed long-distance calls in the UK.

Bell's British company is founded (1878) : from south to north

Less than six months after making his first British demonstrations, the UK rights to the Bell patents had been taken up by a new British company, The Telephone Company (Bell's Patents) Ltd. One of the first telephone lines to be erected was from London's Hay's Wharf, south of the Thames, to Hay's Wharf Office on the north bank.

CHRNOLOGI


CAL EeeeEeeeeeeeEeeeVOLUTION

Eeeee

Eeeevolution of telecomEVOLUTEEEEEEEEEEEEION IMPORTANT EVENTS IN HISTORY OF TELECOMMUNICATION

November 1850 The first Experimental Electric Telegraph Line was started between Calcutta and Diamond Harbour.

October 1851 The Line completed and opened for East India Company’s traffic.April 1852 Dr. O’Shaughnessy’s report on successful working of the

experimental Line landed before the Bengal Govt. November 1953 Construction started of 4,000 miles of telegraph lines connecting

Calcutta and Peshawar in the north via Agra and Bombay through Sindwa Ghats, Bombay and Madras in the South as well as Ootacamund and Bangalore.

October 1854 The first Telegraph Act enacted.February 1855 Electric telegraph opened to public traffic.

1858 First Indo-Ceylon cable laidJanuary 1865 First Indo-European telegraph communication effected.

1867 A new cable laid between India and Ceylon. 1871 International Telegraph Conference at Berne and Rome. 1873 Duplex Telegraphy introduced in India between Bombay and


EVOLUTION OF TELECOM IN INDIA

Calcutta 1873 Indigenous manufacture of cables for river crossing by Telegraph

Workshops, Alipore.

August 1875 The first Private Telephone line supplied by the Telegraph department.

August 1877 Indian Telegraph Department erected telegraph line betweenSrinagar and Gilgit on behalf of the Maharaja of Kashmir.

1878 For the first time (except the first year) the receipt of the IndianTelegraph Department exceeded the expenses, netting a surplusOf Rs. 182,128.

November 1881 Licences granted to Private Companies to operate TelephoneSystems at Madras, Bombay, Rangoon, Calcutta.

January 1882 Opening of telephone exchange at Bombay.October 1885 Upper Burma Campaign – I.T.D. helps in providing communi-

cations for swift advance. Introduction of Quadruplex telegraphy and copper wire for transmission.

1886 Copper wire for transmission between Bombay and Madrasinstead of iron wire.

1905 Control of Telegraph Department transferred from P.W.D. to Commerce and Industry Department, except for matters connected with Buildings and Electricity.

1906 Baudot system introduced between Calcutta and Bombay, and Calcutta and Rangoon.

August 1907 Central Battery working of telephones was first introduced in Kanpur.

December 1907 Women signalers employed for the first time. 1908 Wheatstone working between London and Calcutta, Madras and

Rangoon.

1909 Wireless Telegraph Traffic was maintained with ships at-sea from Calcutta stations at Diamond Island, Table Island, etc.

April 1910 Birth of Technical Branch as a separate organization for dealing with the technical matters under Electrical Engineer-in- Chief.

December 1910 Telegraph Department awarded a gold medal in the United Provinces Exhibition held at Allahabad.

1910-11 Introduction of Circle Scheme in the department and decentralization.


1912-14 Amalgamation of Postal and Telegraph Department under a single Director-General. Reversion of control of P&T again to P.W.D.

1913-14 First automatic exchange at Simla with a capacity of 700 lines with 400 actual connections.

April 1919 Lady operators employed in Simla Exchange. 1920 Madras-Port Blair route for Wireless Telegraph opened.

August 1921 National Cash Registers introduced in Calcutta C.T.O. for the

first time. 1922 Department erected a line for Tibetan Government from Gyantse to

Lhassa.

1923 Long distance dialing (90 miles) introduced between Lahore and Lyallpur.

1923 First Trunk Telephone Circuit in Burma established between Rangoon and Pegu.

1924 Floods and cyclone interrupted Telegraph Traffic throughout India.

1925-26 Conversion of Delhi Manual system to Auto System. Deluxe telegrams for greeting messages with foreign countries introduced.

23rd July 1927 Radio-Telegraph started working between U.K. and India. The beam station at Kirkee and Dhond opened by Lord Irwin and greetings exchanged with the King of England.

May 1933 Radio-Telephone communications between England and India opened by India Radio and Cable Communication Co. Special Trunk Exchange was installed at Kirkee.

December 1936 Indo-Burma Radio-Telephone service started functioning between Madras and Rangoon.

1936-37 Use of Trunk Lines for broadcasting programmes introduced.

1937 Burma and Aden Telegraph Systems, which were a part of Indian Telegraph System, separated.

1937 Deluxe Telegram with foreign countries introduced.

1938-39 Construction of short wave and medium wave wireless telegraph receivers in a number of stations and direction finding stations at Gaya and Allahabad.

1942 Bombay Australian wireless Telegraphic service inaugurated.February 1942 Bombay-China Wireless Service inaugurated. Training center at

Calcutta transferred to Jabalpur. 1943 The Jabalpur Telegraph Workshop started.


1942-47 Telecommunication Development Scheme came into operation.A Telecommunication Development Board was set up.

August 1944 Bombay-New York Wirless Telegraph Service was commissioned into service.

1947 India was represented at the important Atlantic City InternationalRadio Conference.

1947 Direct Telephone link to Kashmir and Assam.1st June 1949 Introduction of Hindi telegram in Devanagari script.

1949 Wireless Station commenced functioning at Srinagar. 1949-50 State Merger Scheme; the P&T gradually took over the respective

State P&T Systems.

January 1950 India-Afghanistan Wireless Telegraph Service inaugurated. Radio-Telephone Service between India and Nepal inaugurated.

October 1950 The Wireless Telephone Service between Indonesia and India opened.

March 1951 The First Asian Games held at Delhi was conveyed by a direct Radio telephoto service between India and Japan. Innovation of Radio-Telephoto Service.

December 1951 Launching of S.S. Jalapushpa of Scindia Steam Navigation Company at Vizagapatam by Shri N.V. Gadgil from Bombay through telegraph circuits.Wireless Telegraph link to Thailand.

June 1951 Wireless Telegraph link to Moscow.July 1951 Wireless Telegraph and Telephone link to Egypt.

First Toll Cable : Delhi-Ghaziabad.

September 1951 Wireless Telegraph and Telephone link to Iceland.Mar/Aug 1952 Wireless Telephone link to Iran/Japan. 1953 12 channel carrier systems introduced. 1953 First Automatic Exchange in Calcutta. Telex Service in Bombay.

First 12-Channel Carrier Systems. Introduction of Frequency Modulation. Mechanisation of Telephone Revenue Accounting.

July 1959 First Coaxial route between Delhi-Agra commissioned.November 1960 First subscriber trunk dialing route commissioned between Kanpur

and LucknowDecember 1965 First microwave route between Calcutta-Asansol openedFebruary 1967 First crossbar-local exchange commissioned at Mambalam – Madras.

December 1967 First crossbar trunk automatic exchange out into service at Madras


March 1975 First PCM system between city and Andheri telephone exchanges commissioned in Mumbai.‘Advanced Level Telecom Training Centre’ commenced training activities from Delhi to be eventually shifted to its own campus in Ghaziabad.

1976 Installation of SPC gateway telex exchange and introduction of International Subscriber dialed telex service.First Digital Microwave System introduced in Calcutta Junction network

1979 First optic fibre system for local junction commissioned at Pune.

1980 First satellite earth station for domestic communications established at Secunderabad (U.P.)

1982 First SPC electronic digital telex exchange commissioned at Bombay.

1983 First SPC analogue electronic trunk automatic exchange commissioned at Bombay.

1984 ‘Centre for Development of Telematics (C-DOT) was established as a society for development of digital switching system.

1985 First Mobile Telephone Service introduced at Delhi.First Radio Paging introduced in Delhi.

1986 ‘Mahanagar Telephone Nigam Limited’ and‘Videsh Sanchar Nigam Limited’ were established.

1987 First digital coaxial 140 Mb/s between Ahmedabad and Rajkot commissioned.

1988 International gateway packet switch system commissioned at Bombay.

1991 I-Net exchange commissioned.Inmarsat coastal earth station at ARVI to provide maritime communication.Voice Mail Service (VMS) introduced in Delhi.

1994

Announcement of National Telecom Policy.Cellular telephone service started in Calcutta and Delhi.Internet service provided by VSNL.ISDN service started commercially.

1998 New ISP Policy was announced.

1999 New Telecom Policy .DOT is separated into two organs- DTS and DTO.


2000 Telecom disputes, settlement and Appellate Tribunal was established.National Long Distance Service opened for private competition. Bharat Sanchar Nigam Limited is born.

2002 VSNL came under private management. International Long Distance Service opened for private competition.Internet telephony was started.

2005 BSNL launched Broadband services


CHAPTER - II

ERECTION OF SUBSCRIBER LOOP FROM DP POINT TO SUBSCRIBER PREMISES

1.0 Drop wire and its installation

1.1 Description: ( Drop wire)

The drop wire normally used in communication is of two hard drawn cadmium copper conductors 1.25 mm or 0.91 mm diameter laid parallel side by side and covered with black PVC of hard grade insulation extruded over them in one operation. A ridge is provided between the two conductors so that

Figure : 1

they can be separated into two fully insulated conductors without any injury to the insulation of the individual conductors. A fin on one side of the insulation moulding of the cable facilitates identification of conductors. A cross section of the wire is given in Figure : 1

This drop wire has high tensile strength, adequate conductivity and good electrical insulation with excellent mechanical resistance for outer protective covering.

1.2 The drop wire can be used in the following typical situations subject to the limitations imposed by transmission considerations and economics of installation. Direct connection from cable terminal to the subscriber premises. The loop leading into the subscribers premises in continuation of an aerial line. In congested areas to lighten the load on loaded alignments and to reduce the incidence of failure and faults due to contacts.


IDENTIFICATION FIN

AB

C

D

At power crossings where it is not possible or convenient to provide the usual guarding arrangements in full.

1.3 Advantages of drop wire

Self-supporting drop wire provides reliable service under extreme climatic conditions and has a fairly long life.

The use of self supporting drop wire in place of bare GI wire for subscribers telephone loops has several advantages, some of which are detailed below: Eliminates the necessity for careful regulation of the dip to avoid contacts; Eliminates fault liability due to contact with twigs and foliage, Makes for a neat installation in the subscribers compound or premises, The method of fixing is simple. A suspension wire is not required for supporting the

cable. Any alteration in the position of the lead-in can usually be made easily, The use of protective devices at the subscriber’s premises can be dispensed with, provided bare overhead wires are completely eliminated.

1.4 Specification:

Standard diameter of bare 1.25 mm conductor. Standard external dimensions 3.3x5.8 mm of finished drop wire. Standard wt. of bare conductor 11.27 kg/km. Standard wt. of drop wire cable 40 kg/km. Maximum loop resistance for standard- 36.62 ohms per Km. at 20o centigrade. Minimum breaking load of bare conductor - 85 kg. of standard diameter. Minimum breaking load of drop wire cable - 170 kg.

The drop wire manufactured by M/s Hindustan Cables Ltd. Rupnarainpur will however, have the following electrical and mechanical properties:-

Standard diameter of conductor - 0.91 mm Standard external dimension of - 2.69 x 5.64 mm. finished drop wire Standards wt. of bare conductor - 5.97 kg/km. Standard wt. of drop wire cables - 28 kg/km. Maximum loop resistance for standard - 66.64 ohms diameter per km. at 20 o

centigrade Minimum breaking load of drop wire cable - 86 kg.

The finished cable supplied by M/s Hindustan cables Ltd. will normally be in lengths of 500 metres or its multiples.

1.5 Installation :

(a) Hardware Accessories :-


The hardware accessories required for erecting the drop wire have been standardized and are indicated in TRC Specification No. 52-123/84-TRC/85. These accessories substitute the accessories indicated in ITD Specification No. S/WZ-101. This provisional Engineering instruction is supplement to E.1 line and cables -3020.

The following accessories are required to erect drop wire.

1.6. Drop wire distribution clamp (Figure: 2)

The Distribution clamp is intended for suspending the self-supporting drop wires (0.91mm dia) at distribution points and intermediate points on poles. The clamp is made of stabilised reinforced plastic material capable of withstanding continuous exposure to all types of weather conditions encountered by overhead telephone lines in the country.

1.7 Support clamp with U- Back (Figure: 3,4)

The support clamp is intended for supporting the Distribution clamp. The support clamp is first fixed on the channel iron ( C.I.) bracket with U- Back. Distribution clamp is attached to the support clamp hook by means of any of the three holes provided in the distribution clamp as per requirement. More than one support clamp may be fitted on the channel iron bracket. Suggested spacing between two support clamps on a bracket is 20 cms. One support clamp is able to support two distribution clamps and thus two-drop wires. The support clamp assembly is made of hot dip galvanised steel or hooks welded to iron strip.

1.8. How to use Support clamp and distribution clamps at

(i) Terminal point,(ii) At intermediate points.

At Terminal Point:-

The support clamp is first fitted on to the channel iron bracket. The drop wire is next taken round the grooves of the Distribution clamp. At terminal point, the drop wire to be terminated is brought straight at the middle hole neck of the Distribution clamp from the lower side (Figure: 5). It is turned back around the neck, wrapped around the back hole neck and brought to the lower side of the front hole neck through the gap between the middle hole and the front hole. The back hole of the Distribution clamp is attached to the hook of support clamp.

For small angle, the position of the hole in the Distribution clamp is changed according to convenience. At terminals any of the side holes of the Distribution clamp is utilized. The position of the Distribution clamp is shown in Figures 6 and 7, if the drop wire is to run along the left direction along the alignment. If the drop wire is to be run to the right direction, the arrangement will be like Figure : 8. At heavy angles and intermediate angle termination post, two different support clamps and distribution clamps are to be used. In both the cases, the drop wire is fixed to the drop wire clamps as for termination but the drop wire is not required to be cut. In normal G.I.


wire lines, wires are terminated and jumpered, in case of drop wire, the wire need not be cut for termination

1.9. At intermediate point:-

Where the line length is more than one span, the drop wire has to be supported at the intermediate poles; some support clamps and Distribution clamps are used for the purpose. Support clamp is first fitted on to the channel iron bracket in the manner similar to the method used at the terminal point. The drop wire is then run through the Distribution clamp as shown in Figure: 9. The drop wire is taken around the upper side of the middle hole neck and lower side of the back and front holes necks as shown in Figure: 10. The Distribution clamp is next fitted on one of the hooks of the support clamp by using its middle hole as shown in Figure: 11.

1.10 Precaution: -

In order to prevent the Distribution clamp from falling off the hook because of high velocity wind vibrations etc, a wire taken through the bottom hole of the support clamp should be tied to the open end of the hook as shown in Figure: 12.

Drop wire should never be taken among the Electrical Service leads. It is observed in many occasions that the drop wire is run along with bunches of electrical service leads even in to the subs offices. This gives lot of chance for direct contact with the power leads where ever the insulation has failed. So it should be made a point not to run the drop wire near to the electrical leads.

1.11 Joints: -

Normally the drop wire should run without any joint right from the D.P. to the window (where the subscriber office is having conduit wiring) and up to the Rosette in all other cases. The joint should be avoided as far as possible. The provision of drop wire from DP to Sub office is shown in Figure: 13.

1.12 Joint between two-drop wire cable:-

a) Wherever it is necessary to join two drop wires, it should be done at a point of fixture. The wires from both the directions should be terminated at two distribution clamps. The loose ends should be connected by twist joints with minimum of 10 close twists and then soldered. The joints should be staggered and lapped individually by adhesive PVC insulation tape. The lapping should extend about 12 mm on both sides of the joint.

b) Joint between bare line wire and drop wire:- Cadmium Copper wire should be used for binding and then soldered.


FIGURE : 2 DISTRIBUTION CLAMP.


FIGURE : 4. SUPPORT CLAMP.


FIGURE :. 3 U.BACK


FIXING OF DROP WIRE IN LINE FIGURE : 10


FIGURE :. 9

FIGURE :. 8


FIGURE :. 12

FIGURE :. 11

FIGURE :. 13


FIGURE : 14

1.13 Guidance for Protective device.

a) If the drop wire is taken from an overhead alignment it should be terminated in a protective device at the subscriber’s premises if the conditions require such protection.

b) If the drop wire is taken from a D.P. and if no bare over head wire is involved the connection can be taken straight to the subscriber’s rosette.

1.14 DIP :-

The following table gives the dip that should be allowed:-

Span Size of conductor of drop wire Dip

70 meters 1.25 mm 120cm



35 meters 0.91mm 60cm

considering the large dip that is required when span length is increased, normally span for 1.25 mm drop wire should be limited to 50 M and for 0.91 mm to 35M. The dip can be regulated approximately by means of bamboo with marker wire as usual.

Figure: 14 shows the complete wiring from D.P. to subs office by drop wire installation of new telephone connection.


CHAPTER III

PROTECTIVE ARRANGEMENTS & TERMINATION OF EXCHANGE LINE AT SUBSCRIBER PREMISES

LINE JACK UNIT : (RJ – 11)

1.0 SCOPE: -

This topic covers the generic requirement of materials, dimensions, mechanical and electrical performance for Line Jack Unit suitable for connecting subscribers telephone instruments and any other voice/non-voice terminal (both Passive and Electronic) to telecommunication systems,(Any Telephone exchange) in Indian Telecom Network. The requirements are specified to ensure reliable electrical contact and mechanical compatibility between Plug and Jack. The plug and Jack shall be 6 way as shown in the diagram enclosed. The number of pins shall be 2.

2.0 GENERAL: -

The LJU comprises of a jack, which has the following general requirements: -

2.1 Jack: The jack is a single moulded device carrying metallic contacts designed for engagement with corresponding plug pins and having provision for direct termination of the exchange lines or wires from another jack. The jack on which the exchange lines are directly terminated shall be called the Line Jack Unit (LJU) and that used for parallel telephone connection in the subscriber’s premises as extension line jack unit.

2.1.1 A self closing spring loaded shutter shall be provided to shield the line jack when the Plug is removed. This shutter shall be flush mounted on the front face of the Jack.

2.2 Plug: A device carrying metallic contacts in the form of pins or fingers intended for engagement with corresponding jack contacts for the purpose of connecting telephone or other devices to jack.

3.0 FACILITIES: -

The Line Jack Unit shall have provision for direct termination of Exchange line. The plug connected to the line cord of the telephone instrument when inserted into the jack shall extend the exchange line to the telephone instrument.

4.0 TECHNICAL REQUIREMENTS

4.1 Components:

4.1.1 The Jack shall consist of: -

(i) The necessary profiles etc. as to match the plug.

(ii) A lock & release latch enabling user to connect or disconnect equipment at will.


4.1.2 The line jack Unit shall comprise of printed circuit board of FR –3 or better grade. PCB shall be firmly mounted on the front cover with screws. Electrical continuity between jack contacts and exchange line termination shall be through PCB tracks only. No external wiring is permitted.

The following components shall be mounted on PCB:

a. A condenser of 2.2 mf in series with 20k. Ohms ½ Watt Resister.b. A gas discharge tube as per clause 4.1.3. c. Screw in type connectors with an eye to accept thick conductor drop wire (0.5mm to 1.2mm).d. A Jack to connect the telephone instrument.e. A back cover to mount the LJU on the wall.

4.1.3 The modular type jack shall have provisions for incorporating a GD Tube, 20k-Ohm Resistance in series with 2.2 mf Capacitor. The provision of GD Tube is preferred. However in all lightning prone areas ( Hilly / Coastal areas) the line jack unit shall be equipped with GD tube. The PCB track from line terminals to GD tube (as shown in figure 3) shall be wide enough to sustain the current flowing during life test on GD tube.

4.2 Electrical Parameters: 4.2.1 The insulation resistance between any combinations of terminals and ground shall be

minimum of 100 Mega Ohms at 250 Volts DC.

4.2.2 The contact resistance shall not exceed 0.1 Ohms with interface jack and plug in their normal mated condition.

4.2.3 Dielectric strength of the line jack measured between any two terminals during one minute test shall not be less than 1000volt R.M.S. The leakage current shall not exceed 100 Micro Ampere during this test.

4.3 Termination of Exchange Line:

4.3.1 The Line Jack Unit shall have provision for terminating and extending exchange line on Terminals a & b.

4.3.2 Assignment of contact numbering for the Plug & Jack are given in Fig. 1 & 2 . Circuit diagram is as per Fig. 3.

4.3.3 Provision shall be made for Four Wire Terminations in Two Terminal Blocks.

The Terminals to be used for the exchange line shall be designated as

Terminals a, b. The remaining Two Terminals shall be interconnected to these

terminals through PCB Tracks to provide for a parallel connection.

5.0 Material for connection:

The termination arrangement of line wires in Line Jack shall be screw-in type. The brass screws used for this purpose shall be conforming to the relevant I.S.


specification (for electrical use). The finish shall be nickel plated and it shall be corrosion proof. It must withstand salt spray test.

5.1 Workmanship and Finish:

The workmanship and the finish shall be of high order free from any tool marks wave formation and roughness. The covers shall be with glossy finish. Screws shall fit correctly without any play and shall not have damaged heads. The holes and threads shall be accurate, straight and free from burrs. The mounting screws fixing the front plate with cover shall be protected by antislip feature.

The contact springs for the reception of the pins of the plug shall be so shaped and smooth at the point of entry as to provide easy access for the pins. They shall be such as to ensure non-resistive electrical contact with appropriate pins over a long period under normal service conditions.

5.2 Markings:-

5.2.1 The front cover of the jack, having the PCB and the Jack, shall have the manufacturers identity mark embossed at suitable place along with the markings for batch number and the year of production etc.

5.2.2. Terminal blocks:

Markings of the tag number or designation shall be done so as to be legible and long lasting.

5.2.3 PCB:

Printed circuit boards shall carry the markings on the components as well as on the PCB's with component values clearly indicated. The line wire termination shall also be indicated on the PCB.

5.2.4 Mounting Holes shall be clearly embossed.

5.2.5 Inlet exchange wires of break through holes shall be easily identifiable.

6.0 Physical Environment :

LJU shall be capable of working under tropical conditions prevailing in various parts of India. Atmospheric dust, industrial fumes, coal dust. etc. are likely to be present in the atmosphere at many places and these should not have any adverse effect on the LJU. It shall be capable of working in the temperature range of –10o C to 550 C with relative humidity ranging from 10 to 95 %.

6.1 Insulation:

The insulation of the jack and plug contribute to overall insulation of subscriber's telephone fittings and shall not be less than 50 M ohms when measured after keeping the samples for 6 hours in a chamber maintained at 95% RH and 27 ± 5 degree C. The


insulation shall be measured with 250 Volts megger of suitable range. The value of insulation at room temperature shall not be less than 100 M ohms.

6.2 Life Tests

6.2.1 The spring loaded shutter shall be able to sustain a life test for 2000 operations.

6.2.2 Effectiveness of the contact

The voltage drop between individual jack contact and a corresponding plug pin after 1000 insertions of plug in the jack shall not exceed 10 mV at 100 mA. ( This is a sample test to be conducted manually ).



04

06

05

a1

a

b

b1

10

20

30

20 KOHMS

2.2 MICROFARADS

JACK

TERMINAL BLOCK

FIGURE –3 CIRCUIT DIAGRAM OF LINE JACK UNIT

CHAPTER IV

TELEPHONE INSTRUMENTS

GENERAL FEATURES OF ELECTRONICPUSH BUTTON TELEPHONE

INTRODUCTION

The EPBT instruments are being manufactured in India with foreign know-how from (1) M/s

Face ITT, Italy, (2) M/s Ericsson Sweden, M/s Siemens, West Germany (See Appendix I). It is also

being indigenously developed and produced by M/s I.T.T. There are two versions of EPBT, viz.

1. Decadic - Can be used in Conventional or Electronic Telephone

Exchange

2. D.T.M.F. - Used in Electronic Exchange.

The basic difference between a Rotary Dialler and EPBT is in the components used. In the

EPBT normally use the IC each for dialling, speech and alert functions.

ITT TypeEricsson Type

Siemens Type Face Type

1. Alert or Ringer Cct (Piezo Buzzer)

Siemens JCS124A

TexasTCM 1506

ICLs 1240 PSB 6520

2. Dial Cct.a. Decadic

b. DTMF

-SCL 2560G

-

-PhillipinesOM 1032P

RIFA PDB3535

-SCL 2560

S 2559E

S 2560G

TCM 5089

3. Speech Cct.

IC PBL3726/6

PBL 3726/6 TEA 1060 TEA 1060

4. Special Features

Linear MicroPhone

Electro-magnetic Microphone

Piezo- Electric Transducers(no moving part)

Moving coil type Transducer for Trans. and Receiver. They are interchangeable

SPECIFICATION OF THE TELEPHONE INSTRUMENT

The important parameters of the specification for the push button Telephone Instrument

prescribed by the Indian Telecom are as follows :


Send Reference Equivalent :

(SRE) for 0 line = + db

SRE for limiting line = + 10.5 db including line (3.5+7.0 line)

Receive Reference Equivalent (RRE) for 0 Line

= -1db

RRE for limiting line = +2.5 db (-4.5 + 7.0 line)

Side Tone Ref. Equivalent (STRE) = +8 to +22 db

Noise = Less than –65 db mp

Echo return loss = Greater than 16 db

Stability balance = Greater than 12 db (at 300 to 3400 Hz)

Insulation= Maximum 5 Megohms at 250 V DC for 5 seconds.

Subscriber loop resistance = Minimum 1000 ohms.

Distortion = Less than 5%.

Level Control = Maximum permissible current 60 mA.

Overall Reference= Not louder than +2 db at 0 Line and not quieter line +3 db on limiting line.

SRE for 0 lineSRE for limiting lineSRE for 0 line

= +6 + 2.5 = +3.5 to 8.5 db.= +1 + 2.5 = -1.5 to +3.5 db.= -3 + 2.5 = 5.5 to -0.5 db.

RRE for limiting lineDRESide toneRef. equivalent (STRE)

= -8 + 2.5 = 10.5 to –5.5= 20 db (including line loss)= more than 10 db

Noise :

(a) Send direction = Less than –65 db mp.

(b) Receiver Direction Insulation Di-electric test

= Less than 40 db.= Minimum 50 megaohm at 250V DC= 240V at 50 Hz for 30 sec.


Radio Frequency Interference (RF-I)

= The instrument should be projected against RFI

Subscriber loop resistance Cross talk Insertion loss

= 1300 ohms maximum= Better than 70 db= Less than 1 db between main and

extension

Maximum DC Loop Resistance Distortion(a) Total(b) Odd harmonics

= Less than 1800 ohms including telephone set

= Less than 3%= Less than 2%

Side Tone Distortion Level control(a) Send direction(b) Receive direction

= Less than 10%

= Less than 3V and less than 3 db= Less than 120 db peak at 120 UPA

pressure

Protection against over voltage and reversal of the limbs of the line

= To be provided.

Advantages of EPBT

Push Button Telephone meets the following requirements for a standard telephone.

(1) It has an attractive appearance and performance.

(2) It has a form and shape in keeping with modern home and office decors.

(3) It has better speech fidelity with electronic transmission circuit and linear microphone.

(4) No wear and tear due to absence of mechanical moving parts.

(5) Electronic tone ringer using piezoelectric disc provides excellent sound generation and makes it

possible to select various sound levels.

(6) Decadic pulsing circuit offers the last number redial facility. The last dialed number is stored

automatically when the handset is replaced and can be redialed any number of times until a

new number is dialed.

(7) DTMF telephones are normally supplied for use with modern stored program controlled

switching systems such as E-10B, Fetex, C-Dot etc.

(8) Human fatigue introduced during repeated dialing on conventional rotary dial telephone is

avoided.


(9) Transmission of erratic pulses and there by landing on the wrong number due to wear on

metallic/plastic moving parts involved in conventional dials are eliminated.

(10) Longer life is ensured due to electronic circuitry.

(11) Dialing can be faster by pressing digit buttons one after the other instead of waiting for each

digit pulses to go on the line.

(12) A light emitting diode indication shows the outputting of digits to the exchange while dialing

and makes the establishment of calls more lively and pleasant.

(13) With little practice, the number can be dialed without actually looking towards key pad, just as

in case of typewriting. This is particularly of great help to blind persons.

Basic Functions of a Telephone

Telephone is a terminal instrument in the speech transmitting and receiving system. Basic

functions of a telephone as terminal instruments are :

1. Dialing function

It should be capable of establishing access to any other telephone within the same

interconnected network.

2. Alert or Ringing function

It should be able to alert the user while the other telephone has successfully accessed it.

3. Speech function

After establishing proper contact between two telephones, it should be possible to carry out

two-way conversation between individuals using the telephone.

The above three essential features are accomplished in a conventional telephone as explained

below :

Speech Function

It consist of Transmitter and Receiver. The Transmitter is a carbon granule microphone and

the receiver is of electromagnetic type (Polarised). The transmitter converts speech signals into


electrical signals for transmission on the line to the distant end where the receiver converts back

these received electrical signals into audible sound information.

Dial Function

Rotary dial is used. The digits dialed are signalled to the exchange by line current

interruptions. The number of Line current interruptions (make and break pulses) correspond with the

digit dialed. In a rotary dial line current breaks occur by means of a switch S1 while the dialer

rewinds (i.e. impulsing contact). To avoid loud clicks in the earpiece, it is necessary to mute the

speech parts of the telephone set. This is done by switch S2 (DONSPRING) that shorts the speech

path during dialing. Impulse spring S1 and spring S2 are operated by the dial.

Calling Functions (Alert)

The ringer used is an electromechanical bell, which is driven by an A.C. Supply of 75V at 17

Hz. A capacity in series with the bell blocks D.C. The ringing voltage is applied to the telephone set

only when the telephone set is on hook.

Fig. 1

Schematic of a Conventional Set

General Principle of Working of Electronic Pushbutton Telephone

In a truly Electronic Push Button Telephone, electronic circuits accomplish all the three

essential functions mentioned above by three different integrated circuits.


SPEECH DIALING ALERT

EAR PIECE

BELL

MIC

Dialing Functions

Two universal methods are used to perform dialing functions in Electronic Push Button

Telephones. These are called Decadic or Pulse dialing and DTMF (Dual Tone Multi Frequency) or

Tone dialing. In case of rotary dialers, it is possible to employ only decadic dialing because of the

basic construction of the dialler itself. A rotary dialler cannot be used for DTMF dialing. Principle of

Decadic dialing is same in Rotary and EPBT.

Principle of Decadic Dialing

Decadic dialing uses the current interruptions to signal the digits dialed to the exchange. The

number of line current interruptions corresponds with the digit dialed. For example, when a number

6 is dialed, there will be 6 interruption of breaks in the line current. When a number 0 is dialed there

will be 10 interruptions in line current. A number 261 dialed with produce a waveform shown in

Fig.2.

Fig. 2Waveform

In a rotary dialer line current breaks occur by means of a switch while the dialer rewinds. In

case of Electronic Push Button Telephones, this is performed by a transistor switch, which breaks the

line corresponding to the number pressed on the keypad.

The interruption rate or the dialing rate is generally 10 Hz.

Principle of DTMF Dialing

This system of dialing was introduced in 1970. In this system digits are transmitted as two

tones simultaneously. This explains the name Dual Tone Multi Frequency. These tone frequencies lie

within the audible range so as to facilitate transmission over the normal 2 wire pair. The tone

frequencies are selected to avoid harmonic interference from speech signals. There are eight


frequencies defined in the DTMF system, four in the low frequency group and four in the high

frequency group. These frequencies and their allocation are shown in Fig.3.

A valid digit is defined as one tone out of the low frequency group together with one tone out

of the high frequency group. For example, when a number '6' is dialed, two tones corresponding to

1477 Hz and 770 Hz are transmitted on the line.

These tones are decoded at the exchange and treated as number '6'.

Fig. 3

D.T.M.F. Frequency Allocation

The advantage of DTMF dialing is mainly the speed of dialing. Time taken to dial any digit is

constant and it is possible to dial typically 7 digits/sec. However, time taken for Decadic dialing

varies with the digits dialed (for dialing '0' maximum time is required). On an average, it is possible

to dial typically 0.8 digits/sec. Thus, DTMF is almost 10 times faster.

The other advantages of the tone dialing:

Use of solid-state Electronic components: consequently minimum wear and tear increased

life.

More compatible with electronic exchanges.

Can be used for end-to-end signaling after the call is established.

The power to dialer circuit has to be derived from TIP RING ONLY. The supply is derived

after polarity protection and protection against voltage transients. The power consumed by the dialer


HIGH FREQ Gr

gRgRGrFREQ. GP

circuit has to be minimized so that a major power is delivered to the speech circuit for its better

operations.

Hence, generally CMOS Integrated circuits are adopted for dialer.

Dialer circuit can be connected to the speech circuit in two modes, i.e. in parallel mode and in

series mode. In most of the circuits, the parallel mode is adopted because of better feed voltages to

both the circuitry.

The supply voltage to the dialler has to be highly regulated. Proper care has to be taken to

extend the supply during dialing when power cannot be derived from the exchange battery.

The dialer IC provides all the control signals required for generating the dial pulses and mute

signal.

During dialing, due to the break and make of the DC loop unwanted clicks are heard in the

receiver. By properly muting the speech circuit, this annoyance is eliminated (comparable with DON

springs in the conventional rotary dial instrument). The muting switch forms part of the dialer I.C.

Fig. 4 (A) Decadic (B) DTMF

Ringing Function

An electronic ringer is basically an OSCILLATOR circuit being activated by the incoming

ring signal, i.e. alternating current of 75V rms and 25 Hz. The output of the oscillator is fed to a

transducer for conversion from electrical to acoustical signal. With the latest technology available, it

is possible to design an electronic ringer with an s signal output, which sounds pleasing, and

sufficiently high sound level output.


Generally, a piezo electric transducer is used as an Electronic ringer. It is otherwise known as

a tone caller.

Piezoelectric Transducers

The basic element in piezoelectric transducer is a piezoelectric diaphragm. This is made up of

a thin layer of piezo material like BATIO. These materials generate a voltage when they are

mechanically deformed. This process can also be inverted, applying a voltage to the material, which

will deform it. This effect is called piezoelectric effect. Let us see how this effect can be used for

generation of sound.

Fig. 5Piezoelectric Transducers

When a voltage is applied to the opposing electrodes, a mechanical distortion occurred by

piezoelectric effect. For disk shaped element this mechanical distortion appears as a force along the

diameter, since the metal plate attached to the element does not expand or contract, the expanded

piezoelectric element forces the diaphragm to bend in the direction shown in Fig.5 (a). Conversely,

when voltage is applied in the opposite direction the element contracts and the diaphragm bend in the

opposite direction [Fig.5 (b)]. Therefore, an alternating voltage is applied alternatively to generate a

sound wave [Fig.5(c)]. The above effect is used in making piezoelectric ringer, piezo microphone

and earpiece.


Electrically the piezo element behaves like a capacitor having capacitance of the order of few

tens of nanofarads. The resonance frequency for a piezo element varies according to the method of

supporting a piezoelectric diaphragm (Fig.6).

Fig. 6

The piezo element is usually attached to a cavity to get a bigger sound. Fig.7 shows an

example in which a piezoelectric diaphragm is attached to the cavity by a support.

Fig. 7


piezoelectric diaphragm

The cavity would have its own resonance frequency. By careful design of the cavity, it is

possible to have two different resonance frequencies, one for the diaphragm and the other for the

cavity. By carefully adjusting these frequencies, it is possible to give a certain bandwidth to the

frequency characteristic of a sound. This is the principle used in the making of piezoelectric

transducers as microphone and earpiece. In these cases a specially designed bounding for

microphone and earpiece is very important to avoid peak in frequency characteristic. In case of

ringer, this is not very important because it is operated in the resonance region.

Since a piezoelectric transducer offers a capacitive load, the amplifiers used to drive

piezoelectric transducers must be carefully designed to avoid instability caused by phase error.

Tone Ringers

Tone Ringers are of two types:

(1) Single Tone Ringer

(2) Multi Tone Ringer

Single Tone Ringer

Single tone ringer has a fixed frequency self-resonating oscillator which is turned ON and

OFF by alternate half cycles of the AC ringing voltage. The circuit requires a regulated voltages

source and the polarity protection block diagram as shown in Fig.8.

Fig. 8Block Schematic of a Single Tone Ringer

Such a Ringer generally produces a very high frequency of the order of 2 to 3 KHz and hence

has certain disadvantages.

(i) Because of high frequency adopted, as people get older their hearing sensitivity at

these frequencies is reduced.


(ii) The ability of people to locate the source of a sound at high frequencies is poor.

The disadvantages of a single tone ringer are overcome in a multi tone ringer.

Multi Tone Ringer

Multitone Ringers are electronically more complex than a single tone ringer. The design of

such a tone ringer is possible because of the development of integrated circuits. As the name

indicates the output of a multitone ringer is produced by switching between two or more frequencies

at a rate determined by the tone ringer circuitry. Block diagram of Multitone ringer is shown in Fig.9.

Fig. 9Block Schematic of a Multi Tone Ringer

The AC ringing voltage is rectified and a DC power supply is derived for the rest of the

circuitry. Protector provided for any short duration over voltages and surge voltages.

Since the input voltage to the circuit vary over a wide range depending on how far the

telephone is from the exchange voltage, regulation is needed so that the voltage applied to the tone

generation circuit is independent of loop length. It also depends on the number of telephones

connected to the same line.

Anti Timer Circuits

Anti tinkle circuits must distinguish between the AC ringing signal and the signal generated

during dial pulsing from the telephone.

One type of anti tinkle circuitry suppresses the spiked dial pulses going to the ringer using

frequency selective circuitry and threshold detection.

Simplest scheme for generating a two tone ringing signal is as shown in the block diagram. It

consists of two oscillators, one to operate at a low frequency of about 10 Hz is the switching

frequency generator of 1000 to 1500 Hz is called the Two tone frequency generator.


Tone

The output frequency of the tone frequency generator is controlled by the switching

frequency. The output of the tone frequency generator is switched over two frequencies depending

on the frequency of the switching generator.

A good impedance of the ringer output circuit is essential to produce maximum power output

from the small input signal power available. A double-ended output stage will help provide an

increased output.

Advantage of Tone Ringers

(1) Possible to obtain pleasant and alerting sound.

(2) Electronic ringers have controllable pitch and level. This helps in identifying ringing of different telephones.

(3) Volume control or the loudness control can be provided.

(4) Components used for electronic ringers are much smaller in size and lighter in weight compared to the conventional bells.

(5) Electronic ringers are more reliable.

(6) Tone ringers output is more detectable by people even with impaired hearing and noisy environment.

(7) Tone ringers can be designed with high input impedance. Hence, it does not load the exchange.

(8) Due to the use of electronic circuitry, it is cost-effective.

(9) The directional variation of sound output is minimized.

Speech Function

In an electronic telephone, the speech circuit is to perform the following functions:

(1) 2 Wire to 4 Wire conversion of the transmission signal (Hybrid function).

(2) Send and receive signal amplification.

(3) To provide correct amount of side tone.

(4) To match an average line impedance.

(5) To provide a path for DC loop current.

(6) Interfacing the transducers.

The equivalent circuit of the telephone system, the exchange line and telephone set replaces

with the equivalent circuits as shown in the Fig.10.


Fig. 10

The basic circuit consists of a balanced wheatstone bridge, the characteristic impedance of

the telephone line ZL forming one arm of the bridge. Two of the bridge arms contain the pure

resistances Z1 and Z2 of the hybrid. Finally, the fourth bridge arm is the balancing impedance ZB

which is an RC network. The bridge balance is obtained when

ZL/ZB = Z1/Z2

This balance is designed for an optimum value of the sidetone attenuation and different

lengths of the telephone line.

The microphone amplifier is converted to one side of the bridge while the receiving amplifier

is connected to the other side. Note that the transmitter now feeds the signal to a transmission

amplifier marked with the symbol AT and the receiver is driven by a receiver amplifier marked with

the symbol AR.

It is useful to understand the equivalent circuit of the telephone set under varying conditions

of send and receive. The "send" equivalent circuit of the telephone is represented by the transmitter

being the source of 'emf' feeding a Series-parallel resistive network. Note that the voltage drop across

the receiver is minimised to that the sidetone is under control.


Fig. 11

This receive equivalent circuit of the telephone is represented by the source of emf in series

with the load feeding a series parallel network. Note that the actual voltage drop across the receiving

device is large enough to drive the device.

The transmitter amplifier provides the required gain and impedance match for the

type of microphone that is used. The output stage is a current generator amplifier driven by

the gain control stage.

The receiver amplifier block diagram is shown in Fig.12. It consists of an input stage of

operational amplifier, a gain control stage and an output stage of PUSH PULL configuration to drive

a low impedance receivers. The gain control stage is a variable gain operational amplifier. Signal

from the line current sensing circuit controls the gain.

Line Balancing

The entire telephone set speech network including the handset, the amplifiers and the hybrid

is shown in Fig.13.


Fig. 12

ZL ZBZ2Z1

Fig. 13

In the overall operation several factors like amplifier gain, hybrid decoupling, the impedance

balancing etc. affect the transfer of energy between the telephone line, microphone and receiver. The

hybrid imbalance affects the sidetone which may result in 'howling'.

The electrical signal imbalancing depends on the hybrid network and the balancing

impedance.

Different makes of Electronic Push Button Telephone employ different types of microphones

and receiver for the speech function, and comparative idea of the different transducers used by the

different manufacturers is given elsewhere in the handout.

Polarity Guard

A telephone set must function properly independent of the polarity of the line voltage applied

to it. This is no problem for carbon microphone types with a rotary dial since there are no polarity

sensitive components in such telephone sets. It becomes a problem when electronic components are

introduced into a telephone set. Transistors and integrated circuits cannot operate if the supply

polarity is reversed and can even be damaged by a reversal. A diode bridge is, therefore, always

connected between the telephone line and the electronic circuits in the telephone set. The circuit

diagram of such a bridge is given in Fig.14.

FIG 14: Circuit Diagram of Polarity Guard


HYBRID DECOUPLING

NETWORK

TO TELEPHONE LINE

LINE BALANCING

Notice that this bridge has no rectifier function; the telephone line already has a direct current supply. A drawback of this polarity guard is the extra voltage drop of two forward diode voltages (1.4V with typical in 4004 type diodes).

Current Limitation : Another important feature of Electronic Push Button Telephones is the necessity for limiting the circuit current within 50 to 60 ma (as per the manufacturers specification) for the proper functioning of the different electronic components.


MOBILE HANDSETSFour New CDMA Handsets from NokiaNokia has launched four new CDMA handsets.Nokia 1255 phone:The value-priced Nokia 1255 phone packs an extra-large feature set into an extra-small package. The 80-gram phone offers productivity tools such as a two-way handsfree speakerphone, voice recorder and a calendar with an alarm clock. Other fun features include two built-in games, 20 ringtones and a selection of user-selectable screen savers. In recognition of the need to stay in touch while minimizing downtime, the Nokia 1225 phone delivers up to four hours of talk time and up to 10 days of standby time. A partial list of additional features includes:

250 contact phonebook Text messaging Stopwatch and countdown timer Internal vibrating alert Easy-to-use Nokia user interface

Nokia 2355 phone:Following the Nokia tradition of delivering high-impact products to all market segments, the new Nokia 2355 phone delivers an ultra-compact, color screen 78-gram fold-style phone to the entry-level market. The 128 x 128 pixel 65K color screen, built-in FM radio and integrated flashlight allow the Nokia 2355 phone to deliver a unique set of features to owners, while the ability to download BREW 1.2 or Java MIDP 1.0 content, such as ringtones, games and screensavers, offers value-added services that meet the needs of both consumers and operators. Other selected features of the Nokia 2355 phone include:

Text and multimedia messaging Integrated speakerphone WAP 2.0 compliant browser 16-chord polyphonic ringtones Calendar with alarm clock

Nokia 2855 phoneFeaturing a bold color palette including metallic-finish indigo or cabernet, the Nokia 2855 phone is Nokia's most affordable Bluetooth technology enabled CDMA handset. The large 128 x 160 pixel 262K color main display is perfect for viewing MMS messages and enjoying the customizable themes that make the Nokia 2855 phone unique for each owner. For maximum productivity on the go, the Nokia 2855 phone features an extensive phonebook with room for up to 500 entries - each allowing for 5 phone numbers, e-mail address, web address and a notes field per entry. Additional features of the Nokia 2855 phone include:

Integrated handsfree speakerphone Voice memo recorder and voice dialing


High-fidelity MP3/AAC ringtone support

Nokia 6165 phoneThe Nokia 6165 phone shares the strong feature set of the Nokia 2855 phone, and builds upon it by adding a full one-megapixel camera with flash and built-in infrared technology to provide support for all major types of connectivity - Bluetooth, USB cable, and infrared. Support for location-based services allow the Nokia 6165 phone to take advantage of mobile applications that take advantage of positioning information for accessing information on nearby points of interest, directions and more. Other unique features of the Nokia 6165 phone include:

Support for capturing, sending and viewing video Classic design with bright chrome accents Streaming video


1255

2355

2355


2855

6165

Nokia 6600 Camera Phone Nokia 6600 Triband GSM Cellular Mobile Phone Product Description:Network: GSM 900 / GSM 1800 / GSM 1900Dimensions: 109 x 58 x 24 mm, 113ccWeight: 122 gType: TFT, 65k color graphicSize: 176 x 208 pixels5-way joystick navigationSelectable themesRingtones: In shared memoryVibration: In phoneLanguages: Major Europe and Asia-PacificPolyphonic ringtonesPhoto phonebookBuild-in handsfreeMMS

User groups


Numbers in phone: In shared memory6 MB shared memoryMMC card slot, 32 Mb card includedSMS: Send/ReceiveClock: YesAlarm: YesData: GPRSInfrared port: YesGames: Yes, downloadableDigital camera (640x480)Video captureBluetoothJavaSeries 60 UISymbian OS 7.0sWAP 2.0POP3/SMTP email clientxHTML browserT9Voice commandVoice memo

QUESTION BANK


CHAPTER II

1. The conductor material of drop wire used in the department is made up of ………………………….

2. The purpose of ridge provided between the two conductors of drop wire is for ……………….3. The purpose of fin provided on one side of the insulation moulding of the drop wire cable is for

……………………………..4. Provision of protective devices at the subs. premises if the drop wire is taken from the DP is

…………..5. The two standard diameter of bare drop wire conductor are ………………..

and…………………….

CHAPTER :III

1) What is the purpose of LJU?2) What is the main requirement of LJU ?3) What are the two purposes , which the jack will serve?4) Mention the parts that a LJU consist?5) What is a Jack?6) What is a plug?7) What are the facilities of a LJU?8) What is the purpose of 2.2mf condenser on the LJU PCB circuit?9) What is the Life Test for the spring loaded shutter of the LJU ?

CHAPTER IV

1. What are the two versions of EPBT?

2. What is the permitted range of side tone reference equivalent?

3. Noise level in the send direction is _____________

4. ___________ dialed no. is stored automatically when the handset is replaced.

5. DTMF stands for ___________________

6. In decadic dialing when ‘0’ is dialed, there will be _____ interruptions in the line current.

7. In __________ dialing, digits are transmitted as the combination of two tones.

8. In DTMF _____ number of frequencies are defined.

9. What is Piezo-Electric effect?

10. What are the two types of tone ringers?


ANSWERS

CHAPTER – II

1. Hard drawn cadmium copper. 2. separating the drop wire into two fully insulated conductors without injury to the insulation 3. identification of conductors. 4. not essential. 5. 1.25mm and 0.91 mm.

CHAPTER – III

1. To connect the subs. instrument (voice or non voice terminal) to the telephone exchange.2. i). reliable electrical contact and ii) mechanical compatibility between plug and jack.3. i) LJU- jack on which the exchange line directly terminates.

ii)extension LJU-the jack used for parallel telephone connection in the subs. premises.4. a jack with a self-closing spring loaded shutter and a plug.5. It is a single moulded device where the direct exchange line gets terminated and gets connected

to pins of a plug of an instrument.6. It is device carrying metallic contact in the form of pins for the purpose of connecting a

telephone to jack.7. i) direct exchange line termination and (ii) to extend the exchange line to instrument through a

plug.8. For extending a condenser click for test form the exchange even when the telephone is removed

from the jack. The spring-loaded shutter should sustain to life test of 2000 operations.

CHAPTER IV

1) Decadic and DTMF2) 8 – 22dB3) Less than -65dBmp4) Last5) Dual Tone Multi Frequency6) 107) DTMF8) 89) When a voltage is applied to the opposite electrodes a mechanical distortion takes place.10) Single Tone, Multi Tone.


Documents

Overhead Lines &Telephony