Analog multibutton telephone keysets
Analog telephone circuit for digital telephone system
Answer supervision over pulse code modulated carrier system and
Apparatus and method for automatically reconfiguring telephone n
Apparatus and method for cost effective caller...
Apparatus and method for detecting telephone line status
Apparatus and method for providing music-on-hold service in...
Apparatus and method for transmitting-receiving CID in a PBX
Apparatus for controlling key telephone station set in key telep
Automated access facilities for use with key telephone systems
Automated access facilities for use with key telephone systems
Automatic redial in a key telephone system having different line