Call progress tone system
Calling signal controller
Communication system having separate unidirectional information
Communication system with assembly carrier unit
Control and interface apparatus for telephone systems
Control of incoming and outgoing calls in a key system
Controlled power supply for key telephone system
Data transmission system of key telephone system
Data transmission system of key telephone system
Dealing communication system
Digital key telephone system and extension terminal device...
Dual line adapter for telephone answering machine
Electronic patching system for telecommunications devices
Graphical user interface workstation
Information processing and communication apparatus
Key telephone apparatus with [automatic] call...
Key telephone apparatus with automatic call distribution functio
Key telephone apparatus with call distribution function
Key telephone interface
Key telephone system