Aircraft communications apparatus
Arrangement for improving a telephone system
Audio communication unit
Audio distribution system
Automatic intercom system for buildings
Automatic phone line re-allocation
Building short circuit react system
Call controlling apparatus and method used for an order-wire...
Collective house interphone system and method therefore
Collective housing intercom apparatus
Communication controlling apparatus for a single-line telephone
Communication system for use in a mine
Control device for a lift
Digitally controlled intercommunications system
Door intercom device
Door intercom system
Door security system
Entrance intercom system
Improved page party system
Integrated communications control device for a small office conf