Nortel Networks 553-3001-211 manual Rx Direction, Clocking modes

NTAK10 2.0 Mb DTI card Page 717 of 894

converted from digital to AMI and sent to the carrier. A transformer provides isolation and impedance matching (75 ohms or 120 ohms).

Rx Direction

The AMI data of the carrier is converted to digital and fed to the input selector as well as the output selector for far end loopback. Clock recovery circuitry within the receiving device extracts the 2.0 MHz clock. This clock generates the frame and multiframe count and sends them to the clock controller as a reference.

Clock controller interface

The recovered clock from the external digital facility is provided to the clock controller through the backplane-to-clock controller interface. Depending upon the state of the clock controller (switched on or off), the clock controller interface, in conjunction with software, enables or disables the appropriate reference clock source.

The clock-controller circuitry on NTAK10 is identical to that of the NTAK20. While several DTI/PRI packs can exist in one system, only one clock controller can be activated. All other DTI/PRI clock controllers must be switched off.

IMPORTANT!

Each MG 1000S that has a digital trunk must have a clock controller

clocked to an external reference clock.

Note: Clocking slips can occur between MG 1000S systems that are clocked from different Central Offices (COs), if the COs are not synchronized. The slips can degrade voice quality.

Clocking modes

The clock controller can operate in one of two modes: tracking or non-tracking (also known as free-run).

Circuit Card Description and Installation