The SLC 96 subscriber loop carrier system: Integration with the 5ESS switching system

A new 5ESS™ switching system peripheral unit provides an efficient integrated interface to Remote Terminals (RTs) of the SLC® 96 digital subscriber loop carrier system. This unit has been named the Digital Carrier Line Unit (DCLU). Each DCLU serves up to six remote terminals [576 Plain Old Telephone Service (POTS) lines]. Each Tl line from an RT terminates on a Digital Facility Interface (DFI) circuit pack, which is the microcomputer-controlled circuit pack used in the 5ESS switching system to interface to Tl lines. The DCLU consists of up to thirty of these DFIs. For purposes of control, the DFIs are separated into two service groups of fifteen DFIs each. There is one control multiplexer circuit pack for each service group. Also there are two data multiplexer circuit packs that are shared by all thirty DFIs. The design of the DFI is described in this paper. The software structure of the 5ESS switching system is explained in general terms and then the software that had to be expanded to support integrated SLC 96 carrier systems is outlined. The paper concludes by describing the topology and traffic-handling capability of the two-stage switching network formed by the DCLU and the remote terminals that are connected to it. The first SLC 96 carrier system integrated into a 5ESS switch went into service on April 14,1984, in Spotsylvania, Virginia.