Expansion port for use in a communication system

Abstract

A system for expanding the number of signal ports accommodated by a base communication system having one or more switching circuits for interconnecting a plurality of local signal ports via a multiple line signal bus under control of a central controller. The expansion system is comprised of a plurality of expansion port circuits connected in parallel to the signal bus, for selectively interconnecting one or more respective remote signal ports to predetermined lines of the signal bus under control of the central controller. Each of the expansion port circuits preferably includes a selector/multiplexer circuit for selectively interconnecting the remote signal port with the predetermined line of the signal bus. According to a preferred embodiment of the invention, the communication system is a telephone system, such as a key telephone system or PABX, and the multiple line signal bus is comprised of a set of junctors. The plurality of local and remote signal ports can be, for instance, subscriber sets, outside telephone lines, call announce units, modems, etc. The system is inexpensive and modular such that the cost for expanding the system is incurred on a "pay as you go" basis, and is not made part of the initial expenditure for acquiring the base communication system.

Dependencies are inferred from the claim text.