1

TIA-1083-A Differences

Minimal changes for telephones with analog interfaces that were covered by TIA-1083.

Transverse performance requirements that had an effective date 24 months after March 2007 publication of TIA-1083 are now mandatory for compliance with the standard.

Frequency response template now applies to transverse magnetic field as well as to perpendicular magnetic field.

2

TIA-1083-A Differences

Main purpose was to add requirements for wireline products with digital interfaces such as VoIP telephones, softphones running on personal computers, etc.

Goal was identical performance requirements for all telephones.

Since magnetic noise sources are internal to the telephone handset, the same test procedures should apply.

Specifying digital input signal equivalent to analog signal being used for measuring desired magnetic field was the challenge.

3

Analog Test Signalfor Measuring Desired Magnetic Field

Borrowed verbatim from 47 CFR 68.316

-10 dBVoc from 900 ohm source applied directly to telephone

For typical 600 ohm telephone, the voltage divider action results in -18 dBV, or -15.8 dBm across the telephone terminals.

-10 dBVoc

900

600- 18 dBV

4

Digital Test Signal for Measuring Desired Magnetic Field

The analog test signal needs to be translated to an equivalent digital test signal.

Telephones with digital interfaces typically encounter a 9 dB higher signal level applied to their terminals than telephones with analog interfaces.

So TIA-1083-A specifies a -7 dBm signal for measuring the desired magnetic field field produced by a telephone with a digital interface.

-15.8 dBm + 9 dB -7 dBm

5

Why 9 dB Difference?

Transmission Plans and Standards

The Public Switched Telephone Network is all digital from end office to end office with no loss between end offices.

Likewise calls placed via the Internet experience no loss between where they enter the Internet and where they leave it.

Thus, the loudness of a telephone call is determined by the acoustic-to-electrical conversion efficiency at the send end and the electrical-to-acoustic conversion efficiency at the receive end.

However, a 6 dB loss pad used in the receive direction for analog lines at the Digital End Office (DEO) to control echo must be taken into account.

6

Transmission Plans

DEO DEO

Internet

ANA

DIG

IP

ANA

DIG

IP

PSTN

0 dBSLR = 8 RLR = 2

7

Receive Implementations

DEO

6 dBD/AAnalogPhone

DigitalPhone

IPPhone

Analog Loop3 dB Avg

Digital Loop0 dB

IP Connection0 dB

SLR = 8

SLR = 8

RelativeLevel

Ref

+9 dB

+9 dB

8

Future of TIA-1083

Devices with a digital interface that do not support G.711 or L16-256 codecs are likely to require test signals other than sine waves and are under study for inclusion in an addendum or future revision of this standard.

An alternative to the A-weighting function that is claimed to provide better subjective correlation over a wider range of interfering noise types is also under study for possible inclusion in an addendum or future revision of this standard.