Nortel Networks 553-3001-211 manual DS-30X loops

Overview Page 33 of 894

DS-30X loops

The line interfaces provided by the line cards connect to conventional 2-wire (tip and ring) line facilities. IPE analog line cards convert the incoming analog voice and signaling information to digital form and route it to the Call Server over DS-30X network loops. Conversely, digital voice and signaling information from the Call Server is sent over DS-30X network loops to the analog line cards where it is converted to analog form and applied to the line facility.

IPE digital line cards receive the data from the digital phone terminal as

512 kHz Time Compressed Multiplexed (TCM) data. The digital line card converts that data to a format compatible with the DS-30X loop and transmits it in the next available timeslot. When a word is received from the DS-30X loop, the digital line card converts it to the TCM format and transmits it to the digital phone terminal over the digital line facility.

A separate dedicated DS-30X network loop is extended between each IPE line/trunk card and the controller cards within an IPE module. A DS-30X network loop is composed of two synchronous serial data buses. One bus transports in the Transmit (Tx) direction towards the line facility and the other in the Receive (Rx) direction towards the CS 1000S, CS 1000M, and Meridian 1.

Each bus has 32 channels for Pulse Code Modulated (PCM) voice data. Each channel consists of a 10-bit word. See Figure 3 on page 34. Eight of the 10 bits are for PCM data, one bit is the call signaling bit, and the last bit is a data valid bit. The eight-bit PCM portion of a channel is called a timeslot. The DS-30X loop is clocked at 2.56 Mbps (one-half the 5.12 MHz clock frequency supplied by the controller card). Thus, the timeslot repetition rate for a single channel is 8 kHz. The controller card also supplies a locally generated 1 kHz frame sync signal for channel synchronization.

Signaling data is transmitted to and from the line cards using the call signaling bit within the 10-bit channel. When the line card detects a condition that the switch needs to know about, it creates a 24-bit signaling word. This word is shifted out on the signaling bit for the associated channel one bit at a time during 24 successive DS-30X frames. Conversely, when the switch sends signaling data to the line card, it is sent as a 24-bit word divided among 24 successive DS-30X frames.

Circuit Card Description and Installation