Call signal detecting device

Caller identification interface using line reversal detection

Circuit and method for automatically cutting off a speech path a

Circuit and method for detecting telephone line status and telep

Circuit arrangement for a telephone station with earth connectio

Circuit arrangement for a telephone station with ground connecti

Circuit arrangement for echo suppression

Circuit arrangement for the connection of line circuits of a dig

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