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Voice control circuit

  • US 4,068,092 A
  • Filed: 09/22/1975
  • Issued: 01/10/1978
  • Est. Priority Date: 11/08/1974
  • Status: Expired due to Term
First Claim
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1. In a voice control circuit of the type comprising a variolosser circuit connected in series with a signal line, and a voice level detecting circuit responsive to the presence of a voice signal having a level above a predetermined threshold value for operating said variolosser circuit, the improvement which comprises a noise control circuit connected on the input side of said voice level detecting circuit, said noise control circuit including a timer which determines as noise the input signal having a constant amplitude and persisting for greater than a predetermined interval thereby detecting the presence of the noise applied to said signal line concurrently with the voice signal, a noise level detector connected to the output of said timer, and a variable attenuator connected on the input side of said voice level detecting circuit and constituted by a plurality of transistor switches controlled by the output from said noise level detector thereby attenuating a signal to said voice level detecting circuit at a value proportional to the level of the input signal, said noise control circuit further comprising a plurality of sets of a timer and a noise level detector, said sets having different operating points and being respectively connected to said plurality of transistor switches, thus producing stepwisely varying attenuation.

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