Circuit for detecting current variations
Circuit for detection of off-hook condition of extension telepho
Circuit for reducing voltage peak in interfacing with a...
Circuit for sensing telephone line conditions
Circuit to detect the hook status and ringing at the CPE end of
Cleaning method for telephone number list and system...
Combined keypad and protective cover
Combined loop current sink, battery detector, and ringing detect
Communication apparatus
Communication between a telephone and a computer system
Communication set with detection of set function and line...
Communication system
Communication terminal device
Communications apparatus
Communications interface providing isolation and ringdown featur
Computer controlled speakerphone for adapting to a communication
Control circuit for voltage controlled attenuator for speakerpho
Coordinating telephones or adjuncts on the same loop
Current mode ring trip detector
Detecting whether a telephone line has been disconnected