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

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Kuriki, Shigeya, Takeda, Hidetomo, Ikoma, Kazuo, Kudou, Tadashi
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Kemeny, E. S.
• Application Number:
  US05/615,705
• Time in Patent Office: 841 Days
• Field of Search: 179/1 P, 179/1 VC, 179/1 HF, 179/1 VL
• US Class Current: 381/94.5
• CPC Class Codes: H03G 3/3015 using diodes or transistors
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H03G 3/34 Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems

Abstract

In a voice control circuit comprising a variable loss circuit and a voice level detector which is connected to control the variable loss circuit, there is provided a noise control circuit. The noise control circuit comprises a timer which discriminates as noise an input having a constant amplitude and persisting for greater than a greater than a predetermined interval, a noise level detector and a variable attenuator connected on the input side of the voice level detector and which functions to attenuate the voice signal in accordance with the detected level of the noise.

Claims

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.