Avaya Nortel Communication Server 1000 Reference page 40

Overview
Figure 4: Typical analog line interface unit block diagram
Coder/Decoder circuit
The Coder/Decoder (CODEC) performs Analog to Digital (A/D) and Digital to Analog (D/A)
conversion of the line analog voiceband signal to and from a digital PCM signal. This signal
can be coded and decoded using either the A-Law or the µ-Law companding algorithm.
On some analog line cards, the decoding algorithm depends of the type of CODEC installed
when the board is built. On others, it is an option selected using a software overlay.
Variable gain filters
Audio signals received from the analog phone line are passed through a low-pass A/D
monolithic filter that limits the frequency spread of the input signal to a nominal 200 to 3400
Hz bandwidth. The audio signal is then applied to the input of the CODEC. Audio signals
coming from the CODEC are passed through a low-pass A/D monolithic filter that integrates
the amplitude modulated pulses coming from the CODEC, and then filters and amplifies the
result. On some of the line cards, the gain of these filters can be programmed by the system
controller. This allows the system to make up for line losses according to the loss plan.
40 Circuit Card Reference
Comments? infodev@avaya.com
July 2011