A TELEPHONE SYSTEM AND ADAPTER THEREFOR

摘要

A telephone adapter (21), comprising an outlet (32) for coupling to a telephone outlet socket having a d.c. voltage across a telephone line connected to a pair of terminals thereof, an inlet (34) for coupling to a telephone extension unit (20), and a switch connected between the outlet (32) and the inlet (34) and operable between a first position in which the telephone extension unit (20) is directly connected to the telephone outlet socket (33) and a second position in which the extension coupling means is a.c. coupled to the line coupling means so as to block said d.c. voltage when the adapter (21) is connected to the telephone outlet socket. The invention also contemplates a system comprising several adapters each connecting respective telephone extension units to a common telephone line, whereby a respective control unit operating in accordance with suitable logic permits connection of one extension unit to the telephone line (11) or, alternatively, to another internal extension unit. Such a system operates as a PABX exchange without requiring a line interface where the telephone line (11) connects to the extension units.