JPS5775053A - Transmission system for control signal of key telephone set - Google Patents

Abstract

PURPOSE:To obtain a key telephone set using the simple time division multiple signal transmission system adapted for transmission of a medium distance, by displaying the synchronizing signal by the absence of a clock signal and by enlarging the amplitude of a control signal more than that of the clock signal. CONSTITUTION:A clock signal (a) and a synchronizing signal (b) are supplied from a generating circuit 18 to a parallel-serial converting circuit 11 and a down signal transmitting circuit 12, and a control signal (c) subjected to time division multiplexing by the converting circuit 11 is transmitted from the down signal transmitting circuit 12. When receiving a down signal (d), a down signal receiving circuit 16 separates it into a clock signal (f), a control signal (e), and a synchronizing signal (h) and supplies them to a serial-parallel converting circuit 17. The clock signal (f) and the synchronizing signal (h) extracted by the down signal receiving circuit 16 are always supplied to a parallel-serial converting circuit 19 for up signal, and an up control signal is subjected to time division multiplexing to become a control signal (i), and this signal (i) is converted to a unipolar control signal (k) by an up signal receiving circuit 24 and is converted to a parallel signal by a serial-parallel converting circuit 25.