Toll restrictor for touch type digit selector

Details Toll restrictor for touch type digit selector Toll restrictor for touch type digit selector

1975-03-27

1976-12-28

Claffy, Kathleen H.

179 18DA, H04M 166

Patent

active

040003809

ABSTRACT:
Improved means are disclosed to prevent a restricted local telephone substation or set from dialing long distance telephone calls by counting the number of digits dialed at the station and preventing the sending of additional digits once the count attains a predetermined number. An electronic counter and a Nand gate latch circuit are arranged in a novel manner in which responsive to the local station going off-hook the Nand gate latch is set into a second condition and the counter is enabled to receive and count pulses from the substation. Means coupled to an output of the counter reset the Nand gate latch to its first condition should the count exceed the predetermined number. Additional means are included in combination by which the dialing of the digit zero as the first digit of a called number also results in resetting the latch.

REFERENCES:
patent: 3681536 (1972-08-01), Pask et al.
patent: 3727007 (1973-04-01), Catlin
patent: 3757055 (1973-09-01), McCann et al.

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