Toll call denial circuit

Claim 2

Call denial equipment for blocking automatic completion of toll calls being placed over a telephone line to a central office comprising means for generating a pulse in response to each dial pulse and on-hook signal for a call on said line, means for counting said pulses from said generating means, means activated at the end of dial pulsing of the first digit for checking the pulse count of said counting means, said checking means generating a call denied signal upon said counting means having counted a predetermined number of pulses, means responding to said call denied signal to block completion of said call, means enabled responsive to said checking means having checked the pulse count of said counting means for subsequently conditioning said generating means to respond only to the onhook signal for said call, and means responsive to the pulse from said generating means in response to the on-hook signal for clearing said counting means, the clearing of said counting means causing said checking means to disable said conditioning means.

Claim 3

The invention in accordance with claim 1 wherein said conditioning means comprises filter means connected to the input of said pulse generating means, and means responsive to said checking means having checked the pulse count of said counting means for changing the time characteristic of said filter means to thereby block the application of subsequently received dial pulses from said generating means.

Claim 4

The invention in accordance with claim 2 further comprising means activated by said generating means for determining the end of dial pulsing of the first digit, said determining means activating said checking means at the end of pulsing of the first digit for thereupon checking the pulsE count of said counting means.

Claim 5

In an automatic telephone system having a central office containing a switching machine equipped to allow toll calls only when a specified digit prefixes a called station number, a dial private branch exchange associated with said office, and a central office line for extending outgoing calls from said exchange to said office, a call denial circuit connected to said line for blocking toll calls thereon comprising means for detecting dial pulsing and on-hook supervisory signals on said line, means responsive to said detecting means for generating a pulse in response to each dial pulse and on-hook supervisory signal on said line, means for counting pulses from said generating means, means responsive to pulses from said generating means for determining the end of dial pulsing of the first digit dialed over said line for the call, means activated by said determining means at the end of pulsing of the first digit for checking the pulse count of said counting means, said checking means generating a denied call signal upon said counting means having counted a predetermined number of pulses, and said checking means generating an allowed call signal upon said counting means having counted other than said predetermined number of pulses, means for blocking dial pulses detected by said detecting means from said generating means, means responsive to said call signals for connecting said blocking means to said generating means, and means controlled by a pulse from said generating means in response to the on-hook signal for clearing said counting means, said checking means causing a termination of the generation of said call signals in response to the clearing of said counting means, and said connecting means being responsive to said signal termination for disconnecting said blocking means from said generating means.

Claim 6

In an automatic telephone system having a central office containing a switching machine equipped to allow toll calls only when a specified digit prefixes a called station number, a dial private branch exchange associated with said office, and a central office line for extending outgoing calls from said exchange to said office, a call denial circuit connected to said line for blocking toll calls thereon comprising means for detecting dial pulsing and on-hook supervisory signals on said line, means responsive to said detecting means for generating a pulse in response to each dial pulse and on-hook supervisory signal on said line, means for counting pulses from said generating means, means responsive to pulses from said generating means for determining the end of dial pulsing of the first digit dialed over said line for the call, means activated by said determining means at the end of pulsing of the first digit for checking the pulse count of said counting means, said checking means generating a denied call signal upon said counting means having counted a predetermined number of pulses, and said checking means generating an allowed call signal upon said counting means having counted other than said predetermined number of pulses, means for blocking dial pulses detected by said detecting means from said generating means, means responsive to said call signals for connecting said blocking means to said generating means, and means controlled by a pulse from said generating means in response to the on-hook signal for clearing said counting means, said checking means causing a termination of the generation of said call signals in response to the clearing of said counting means, and said connecting means being responsive to said signal termination for disconnecting said blocking means from said generating means.

Claim 7

The invention in accordance with claim 4 wherein said blocking means comprises a resistor-capacitor filter connected to said pulse generating means.

Claim 8

The invention in accordance with claim 5 wherein said determining means comprises a one-shot multivibrator connected to said generating means, said multivibrator being triggered by pulses from said generating means in response to dial pulsing to generate an elongated pulse ending after completion of all dial pulsing of the first digit, said checking means being activated by the end of said elongated pulse, and said multivibrator being responsive to the pulse generated by said generating means for the on-hook signal to generate a second pulse for controlling said clearing means to clear said counting means.

Claim 9

The invention in accordance with claim 6 wherein said clearing means comprises a flip-flop connected to said multivibrator, said flip-flop being placed in a prescribed state by said second pulse, and an output signal generated by said flip-flop in said prescribed state for clearing said counting means.

Claim 10

A toll denial circuit connected to a telephone line and comprising dial pulse counting means, pulse generating means for driving said counting means in response to dial pulses and on-hook transitions on the telephone line, a filter circuit connected to the input of said pulse generating means, said filter circuit including a resistor and a first capacitor defining a first timing interval to prevent spurious pulses on the telephone line from triggering said pulse generating means while allowing dial pulses on said line to trigger said pulse generating means, means responsive to the end of the first dialed digit for checking the count of said counting means, and means responsive to said checking means for connecting a second capacitor in parallel with said first capacitor whereby said filter circuit defines a second timing interval to prevent subsequent dial pulses from triggering said pulse generating means while allowing an on-hook condition of said line to trigger said pulse generating means.

Claim 11

A toll denial circuit connected to a telephone line and comprising dial pulse counting means, pulse generating means for driving said counting means in response to dial pulses and on-hook transitions on the telephone line, a filter circuit connected to the input of said pulse generating means, said filter circuit including a resistor and a first capacitor defining a first timing interval to prevent spurious pulses on the telephone line from triggering said pulse generating means while allowing dial pulses on said line to trigger said pulse generating means, means responsive to the end of the first dialed digit for checking the count of said counting means, and means responsive to said checking means for connecting a second capacitor in parallel with said first capacitor whereby said filter circuit defines a second timing interval to prevent subsequent dial pulses from triggering said pulse generating means while allowing an on-hook condition of said line to trigger said pulse generating means.

Claim 12

A toll denial circuit in accordance with claim 8 wherein said connecting means comprises means defining a first path if said counting means indicates a call is to be denied and means defining a second path if said counting means indicates a call is to be permitted.