Channel test unit
Circuit for activating back-up lines
Communication channel switching arrangement
Communication network signalling system link monitor and test un
Communication system and a method, to detect a power exposure of
Device for sequentially altering a communication line for remote
Dial line monitor and control unit
Digital bypass for telephone system
Electric circuit connector with auto-termination
Equipment for sending digitally pre-stored voice announcements t
Fail safe voice system for integrated services for digital netwo
Method and apparatus for performing impedance measurements on a
Method for inspecting transmission channels in a...
Power feeding system using two-wire subscriber lines
Protection and recovery of telephone line interface circuits
Remote unit monitoring system
Remotely actuated switch and protection circuit
Remotely connectable maintenance termination unit
Subscriber terminal circuit for connecting an analog subscriber
Termination unit with maintenance facility