Subscriber loop carrier

An integrated subscriber loop carrier (ISLC) has its T-spans terminating directly in time division switching equipment in the telephone exchange.

This configuration is more efficient than the alternative of having separate copper pairs between each service termination point (the subscriber's location) and the central telephone exchange.

These systems are generally installed in cabinets that have some form of uninterruptible power supply or other backup battery arrangements, standby generators, and sometimes with additional equipment such as remote DSLAMs.

SLCs have been criticized for reducing the reliability of local loops due to their increased reliance on utility power.

However, telephone companies have increasingly been using SLCs, which are notorious for poorly functioning or short-lived battery backup systems, some lasting as little as four hours.