Tone dial toll restrictor

Details Tone dial toll restrictor Tone dial toll restrictor

1978-06-21

1979-12-04

Brown, Thomas W.

H04M 166

Patent

active

041773586

ABSTRACT:
Logic circuits including electronic switching are provided for admitting or rejecting signals from a dual multi-frequency telephone into a trunk line, or toll line, the initiating control of which is provided from a dial tone signal feeding a detection circuit whereby selective recognition of coded signals permits further processing into the trunk line, there being additional, specific logic circuits for preventing further processing of the coded signals when a "zero" or a "one" numerical digit is recognized as the first signal. If the dial tone signal is not detected, the telephone line connected to a telephone is held at a voltage polarity which prevents dialed signals from the telephone from reaching the telephone line. When a dial tone is detected, the line polarity is reversed, thereby permitting dialed signals to reach the line.

REFERENCES:
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patent: 3931476 (1976-01-01), Matthews
patent: 3940569 (1976-02-01), Schonbrun et al.
patent: 4095056 (1978-06-01), Ewen

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