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Telephone call restricting apparatus

  • US 4,188,508 A
  • Filed: 08/21/1978
  • Issued: 02/12/1980
  • Est. Priority Date: 08/21/1978
  • Status: Expired due to Term
First Claim
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1. A telephone call restricting apparatus for connection to a telephone line for preventing the completion of a toll call by a telephone device connected to the line, the apparatus comprising:

  • decoder means for connection to the line, said decoder means being responsive to signals develpoed on said line as each digit of a telephone number is dialed including pre-prefix digits, prefix digits, area code digits, central office digits and local number digits and operative to generate decoded digit signals;

    means for storing at least some of said decoded digit signals;

    means for comparing the decoded digit signals when stored with a prestored list including information relative to whether a predetermined combination of central office digits correspond to a permissible local call, and for developing a first signal when the central office digits portion of said stored digit signals does not correspond to that of a local call;

    first detector means for monitoring said stored decoded digit signals and for developing a second signal when the first digit of said stored decoded digit signals corresponds to a "0" or to a "9" followed by a "0";

    second detector means for monitoring said stored decoded digit signals and for developing a third signal when the second area code digit of said stored decoded digit signals corresponds to a "0" or a "1";

    third detector means for monitoring said stored decoded digit signals and for developing a fourth when the central office digits of said stored decoded digit signals correspond to the number "555";

    fourth detector means for monitoring said stored decoded digit signals and for developing a fifth signal when the area code digits of said stored decoded digit signals correspond to the number "(800)";

    logic means responsive to said first signal or said second signal and operative to develop a sixth signal and responsive to said third signal and operative to develop said sixth signal in the absence of said fourth signal and said fifth signal; and

    means responsive to said sixth signal and operative to abort the call so as to prevent completion of a toll call.

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