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

TIA-1083-A 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.

Analog Test Signal for Measurement of Desired Magnetic Field Borrowed verbatim from 47 CFR dBVoc from 900 ohm source applied directly to telephone For typical 600 ohm telephone, the voltage divider action results in -18 dBV, or dBm across the telephone terminals.

Translation to Digital Test Signal for Measurement of Desired Magnetic Field 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 dBm + 9 dB  -7 dBm.

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 receive direction for analog lines at the Digital End Office (DEO) to control echo must be taken into account.

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