JPH01167785U - - Google Patents

Description

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part of Fig. 1, Fig. 3 is a conventional circuit diagram, and Fig. 4 is a signal waveform diagram of each part of Fig. 3. . In the figure, PHC ₁ to PHC ₄ are photocouplers, A
-SW is an analog switch, HS is a hook switch.

Claims (1)

[Scope of utility model registration request] The main device consists of a main device and a plurality of telephones, and the main device includes a circuit for generating a low frequency pulse for a ringing signal, a control section that detects an incoming call to each telephone and generates a control signal for the ringing signal, and a circuit that generates a low frequency pulse for a ringing signal. In the button telephone device, the response detection circuit includes a circuit that detects a telephone conversation current flowing through a telephone current supply line due to off-hook of the telephone and detects a response of the telephone.
A button telephone device comprising a switch that defines the timing of detecting the presence or absence of the telephone current, the switch being controlled by the output of a logic circuit that processes the low frequency pulse and the control signal. Response detection circuit.