Avaya 1000 Series, Reference

Page: 66 / 700

some trunk 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 trunk are passed through a low-pass A/D
monolithic filter that limits the frequency spread of the input signal to a nominal 200–3400 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 trunk 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.
Balancing network
Depending on the card type, the balancing network is capable of providing either a 600 ohm
or a 900 ohm (or both) impedance matching network. It also converts the 2-wire transmission
path (tip and ring) to a 4-wire transmission path (Rx/ground and Tx/ground). The balancing
network is a transformer/analog (hybrid) circuit combination.
Signaling circuits
Signaling circuits are relays that place outgoing call signaling onto the trunk. Signal detection
circuits monitor the incoming call signaling.
Control signals
Control signals and logic are provided when the trunk is going to be connected to special
services such as recorded announcement and paging equipment.
Serial Data Interface (SDI) cards
The NT8D41BA QSDI paddle board provides four bidirectional asynchronous serial ports for
the system processor, and the QPC841 QSDI card also provides four. Any device that conforms
to the RS-232-C serial communication standard can be connected to these serial ports.
The electrical interface uses either standard RS-232-C signals or a special high-speed
interface that combines the high-speed differential interface of the RS-422-A standard with the
handshake signals of the RS-232-C standard.
The RS-232-C interface is normally used when data rates are less than 19.2 Kbps, and the
cable length is less than 15.24 m (50 ft). The high-speed interface is used when the signal
rates are greater than 19.2 kbps (up to 64 kbps) and/or when the cable length is greater than
15.24 m (50 ft).
Table 9: Serial data interface cards on page 67 shows compatibility between the three SDI
cards and the various switch options.
Overview
66 Circuit Card Reference July 2011
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