ABSTRACT: GR-666 replaces TR-TSY-000666, Issue 1, but contains NO TECHNICAL CHANGES from that original document. It has been issued strictly to conform with the new Telcordia Technologies document format and GR process, and carries a new issue number and date.

A Pair Gain System (PGS) is used to reduce the quantity of outside plant facilities needed to serve telephone subscribers in a local Stored Program Control Switching System (SPCS) by multiplexing and/or concentrating N lines into a smaller number of wire pairs, optical fibers, or radio channels. The PGS is generally used as the equivalent of a metallic feeder plant; therefore, no regauging of metallic facilities from a remote terminal to the customer is normally permitted. This GR describes the interface between an SPCS and universal PGS's. It contains the Telcordia view of generic requirements for that topic.

GR-666, GR-672, GR-674, GR-675, GR-677, GR-679, GR-690, GR-691, GR-692, GR-693, GR-695, GR-697, and GR-698, replaced TR-TSY-000530.