Control signal transmission system of key telephone system

Abstract

Abstract PURPOSE:To make it possible to perform a trunk call and an extension call at the same time, by superposing a control signal on the extension call circuit by the frequency except the audio frequency. CONSTITUTION:When a call signal has come from the trunk lines L1, L2, and call signal is received by the call signal receiver RC in the main telephone set M. TEL, its receiving information is sent to CPU, it is decided by this CPU that a signal has come from the turnk line, and a control signal is generated. This control signal is subject to FS modulation in the inaudible band by the control signal generating circuit FS, and is sent out to the extension call circuits C1, and C2. And as for the FS signal which has been sent out to C1, C2, its waveform is shaped by the waveform shaping circuit WF through the high-pass filter HPF of each telephone set S. TEL and the main telephone set M. TEL, it is input to CPU and is demodulated. And incoming display of the trunk is performed by CPU, and an operator who has been informed of incoming pushes the trunk line switch LK of the telephone set M. TEL or S. TEL.

Inventors

• 👤 Kosuke Hashimoto
• 👤 Hideo Ohashi

Bibliographic Details