Telephone-call prohibit circuit

Details Telephone-call prohibit circuit Telephone-call prohibit circuit

1983-01-04

1984-11-13

Schreyer, Stafford D.

179 18DA, H04M 166

Patent

active

044827873

ABSTRACT:
A circuit for preventing a telephone set from being used without approval, the telephone set including a handset, telephone lines coupled to the handset, a dial pulse signal generator and hookswitches for coupling the telephone lines to the handset and for cooperating with the handset. A circuit is provided for converting the dial pulse signals into a binary code, a prohibit circuit is provided for generating a prohibit signal which prohibits a telephone call when the binary codes corresponding to prohibited dial numbers are input thereto, and an unlock circuit is provided for generating during a predetermined period a control signal which allows a telephone call when the binary codes corresponding to secret dial numbers are input thereto. A transfer switching means is provided for selectively coupling the converting circuit to either the prohibit circuit or to the unlock circuit and for cooperating with the hookswitches. A gate circuit is provided for preventing the passing of the prohibit signal of the prohibit circuit in response to the control signal of the unlock circuit, and a switch is provided for breaking the telephone lines in response to the prohibit signal from the gate circuit. A reset signal is generated to the prohibit circuit when the hookswitches are closed, whereby the prohibit circuit is reset to its initial condition.

REFERENCES:
patent: 4234764 (1980-11-01), Beebe
patent: 4314108 (1982-02-01), Sharuit

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