Toll restrictor for touch type digit selector

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

1975-03-14

1977-03-15

Claffy, Kathleen H.

179 18DA, H04M 166

Patent

active

040126021

ABSTRACT:
Means and methods are disclosed to prevent dialing of long distance telephone calls from a restricted local substation by counting the number of digits dialed at that station and preventing the sending of further digits once the count attains a predetermined number. Means are also included by which the initial dialing of the digit zero, which might enable one to obtain access to the long distance telephone operator, also results in disabling of the telephone dial. The invention includes a pair of Nand gate latches and an electronic shift register; means responsive to the telephone substation being placed in the off-hook or on-hook condition, respectively, for setting the Nand gate latches in a second or first bi-stable condition, respectively; means responsive to the first Nand gate latch going into the first bi-stable condition for inserting an information bit into the shift register; means responsive to the first shift in the register for setting the first Nand gate to its first condition and means responsive to the information bit being shifted into an eighth position for setting both Nand gate latches into the first condition; and means for disabling transmission when the second Nand gate latch is in the first condition.

REFERENCES:
patent: 3681536 (1972-08-01), Pask et al.
patent: 3727007 (1973-04-01), Catlin
patent: 3757055 (1973-09-01), McCann et al.
patent: 3899640 (1975-08-01), Piacente et al.

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