Ringing signal display circuit for 2-wire telephone line - uses angularly offset sensor wires around outside of telephone line with evaluation of obtd. signal differences

摘要

The circuit has a capacitive sensor galvanically sepd. from the line wires coupled to an evaluation and amplification circuit (M,OP,F) for detection and indication of the ringing signal. The sensor comprises four capacitive sensor wires (d1-d4), surrounding a section of the line, supplying respective signals to the evaluation and amplification circuit (M,OP,F), indicating the ringing signal in dependence on the detected signal differences. The sensor wires are pref. arranged in rotational symmetry to one another around the outside of the telephone line and are offset from one another by 90 degrees. ADVANTAGE - Reliable detection of ringing signal for activating optical display etc..