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VOICE-MONITORING CONTROL CIRCUIT

  • US 3,798,382 A
  • Filed: 05/22/1972
  • Issued: 03/19/1974
  • Est. Priority Date: 05/22/1972
  • Status: Expired due to Term
First Claim
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1. A voice-monitoring control circuit for use in combination with electrical switch means connected to a telephone line, where the switch means when closed establishes a talking connection in the line, and when opened breaks such a connection, said control circuit in operative condition comprising a supply of regularly recurring electrical pulses, an electronic digital counting circuit operatively connected to said supply and to said switch means for counting pulses supplied by the former and for effecting, when said switch means is closed, opening thereof on the count of such pulses reaching a predetermined count, said counting circuit being constructed for instantaneous, direct resetting to a zero-count condition from any above-zero count condition, and a frequency-sensitive circuit responsive to a narrow band of voice audio frequencies and operatively connected to said telephone line and to said counting circuit, said frequencysensitive circuit effecting instantaneous, direct resetting of said counting circuit to a zero-count condition on each different occurrence in said telephone line, with a talking connection existing therein, of a voice audio frequency within said band.

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