Analog subscriber/trunk module with shared ringing source and ring-trip

Abstract

An apparatus and method of organizing line interface modules between analog subscriber lines/trunks and a digital switch with the provision for ringing signals which may be shared by a plurality of lines from a single source is described. The ringing signals are intercoupled to any line or lines and transmitted through a common metallic bus which provides immediate ringing for any line, with a shared ring-trip circuit. A software-controlled and/or programmable signal generator in combination with a novel ring-trip circuit is described wherein ringing cadence is generated by connecting the programmable signal generator to a subscriber line for the proper duration and at any desired frequency, whereby multi-frequency ringing can be accomplished under programmable control. A spare line control function within a cluster of telecommunications line circuits is provided such that any telecommunications line circuit can arbitrarily be designated as a spare line, usable to provide temporary service, for example, to a telephone subscriber having a defective line, thereby permitting scheduled maintenance rather than on-demand maintenance. Immediate ringing is provided to groups of analog telephone lines having shared ringing sources and shared ring-trip circuits in a system architecture compatible with a digital switching system.