Subscriber Loop Carrier refers to equipment providing central office-like telephone interface functionality. The SLC RT is typically located in a remote (from the telephone company central office) area with a high density of telephone service such as a residential neighborhood. Two or four T1 circuits (depending on the configuration) connect the SLC Remote Terminal (RT) back to the Central Office Terminal (COT) in the case of a Universal Subscriber Loop Carrier (USLC). An Integrated Subscriber Loop Carrier (ISLC) has its T-spans terminating directly in time division switching equipment in the telephone exchange. One system serves up to 96 customers. This configuration is more efficient than the alternative of having separate copper pairs between each service termination (house) and the central office. The term comes from the SLC-96 trademark of Western Electric. A Subscriber Loop Carrier Circuit system manufactured by AT&T (now Lucent). SLC-96 has its own version of T1 frame synchronization between it and the CO. This interface is the Bellcore TR-008 or the newer GR-303 interface which are specialized versions of T1 intended to allow transparent transport of analog features such as Caller ID, Call Waiting, etc.
