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PROTECTIVE TELEPHONE ALARM SYSTEM

  • US 3,710,024 A
  • Filed: 11/12/1970
  • Issued: 01/09/1973
  • Est. Priority Date: 11/12/1970
  • Status: Expired due to Term
First Claim
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1. A protective alarm for connection to a telephone line and for automatically dialing a remote telephone and delivering an audio message in response to an intrusion, the alarm comprising:

  • a. an audio playback means for providing a programmed signal at its output including a control signal and an audio message;

    b. an electronically operated electromechanical dialing switch means having an energization coil and connected to couple the audio output of said playback means to said telephone line when said dialing switch means is closed and to disconnect the telephone when said dialing switch means is open and having an input for operating said dialing switch;

    c. a control signal responsive circuit means connected between the input of said dialing switch means and said playback means output for causing the closing Of the dialing switch means in response to the presence of said control signal at said output, said control signal responsive circuit means comprising a transistor having its output switching terminals connected to said energization coil and a source of power and having a capacitor connecting the transistor input to the output of said playback means, the transistor being d-c biased to hold the dialing switch means in an open state; and

    d. an impedance matching audio transformer connected to couple the output of said playback means to said telephone line, the primary being connected to the output and the secondary being serially connected to said telephone line and said dialing switch means.

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