| 摘要 |
PROBLEM TO BE SOLVED: To identify a type of an incoming call without addition of a new circuit or the like by waveform-shaping an analog signal from a line network, measuring number of times when number of times of changing of a pulse signal output after waveform shaping from a high level into a low level and from a low level into a high level within a prescribed time and identifying plural types of an incoming call, based on the number of times. SOLUTION: A ringing current from a network is converted into a pulse train by a photocoupler Ph1 and integrated by an integration circuit consisting of a filter resistor R4 and a filter capacitor C2, and a general phone call signal IR, an incoming call transfer alarm signal TIR or an extension call signal SIR is outputted from a collector of a transistor(TR) 1. A microprocessor 1 monitors an output voltage of the TR 1 up to 2016 mSEC for each 32 mSEC, measures contents of output changes and a time and whether the signal is the general phone call signal IR, the incoming call transfer alarm signal TIR or the extension call signal SIR is discriminated, based on the result of measurement.
|
