Identifying circuit for dial-in pulse signal and calling signal of telephone set

Abstract

Abstract PURPOSE:To prevent the malfunction of the facsimile device or the like through identification between the calling signal and the dial-in pulse by monitoring the frequency and the time of the input signal via the timer circuit. CONSTITUTION:The input signals of the dial-in pulse and calling signal are supplied to pulse formation circuit 2 via half-wave rectifier circuit 1. The pulse is delivered with every period of the input signal. With his pulse, the frequency of the input signal is monitored through timer circuit 3, and the continuous transmission time of the input signal is monitored through timer circuit 4 based on the monitor output. As a result, an identification becomes possible between the supplied dial-in pulse of a high or low frequency and the calling signal.

Inventors

• 👤 Kazuhiko Okutsu
• 👤 Norio Kataoka
• 👤 Harumitsu Shimizu
• 👤 Hironari Inagaki
• 👤 Goro Izumi

Bibliographic Details