Nortel Networks 553-3001-211 manual Analog line interface units

Overview Page 35 of 894

A card LAN link bus is common to all of the line/trunk card slots within an IPE module. This bus is arranged in a master/slave configuration where the controller card is the master and all other cards are slaves. The module backplane provides each line/trunk card slot with a unique hardwired slot address. This slot address enables a slave card to respond when addressed by the controller card. The controller card communicates with only one slave at a time.

In normal operation, the controller card continually scans (polls) all of the slave cards connected to the card LAN to monitor their presence and operational status. The slave card sends replies to the controller on the input bus along with its card slot address for identification. In its reply, the slave informs the controller if any change in card status has taken place. The controller can then prompt the slave for specific information. Slaves only respond when prompted by the controller; they do not initiate exchange of control or status data on their own.

When an IPE line card is first plugged into the backplane, it runs a self-test. When the self-test is completed, a properly functioning card responds to the next controller card poll with the self-test status. The controller then queries for card identification and other status information. The controller then downloads all applicable configuration data to the line card, initializes it, and puts it into an operational mode.

Analog line interface units

Once the 8-bit digital voice signal has been received by the analog line card, it must be converted back into an analog signal, filtered, converted from a

4-wire transmission path to a 2-wire transmission path, and driven onto the analog telephone line.

Figure 4 on page 36 shows a typical example of the logic that performs these functions. Each part of the analog line interface unit is discussed in the following section.

Circuit Card Description and Installation