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Primary Examiner: Claffy, Kathleen H.
Assistant Examiner: D'Amico, Thomas
Attorney: Brown; Laurence R.

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Title: Variable gain amplifier controlled by ambient noise level

Abstract: An audio amplifier system is provided comprising a variable gain amplifier adapted to receive an input signal, means for detecting periods when the input signal falls below a predetermined level, and sound transducer means arranged to provide a signal proportional to the sound level in the area or part thereof covered by the system for controlling the gain of the amplifier. An inhibitor is provided which is arranged to be controlled by the detecting means so as to prevent any change of the gain of the variable gain amplifier except during periods when the input signal falls below the said predetermined level.

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Inventors: Munson, Robert Thomas (St. Peter, GC)
Hodgson, Philip (St. Martin, GC)

Application Number: 455373
Filing Date: 1974-03-27
Publication_date: 1976-01-20
Assignee: Television Research Limited (St. Helier, GC)
Primary Class(es): 381/57
Other Classes:
US Patent Ref:

2503391	Apr, 1950	Kannenberg	179/1.
2564437	Aug, 1951	Kannenberg	179/1.
2575990	Nov, 1951	Augustadt	179/1.
2616971	Nov, 1952	Kannenberg	179/1.
2668874	Feb, 1954	Augustadt	179/1.
3296373	Jan, 1967	Suganuma	179/1.
3410958	Nov, 1968	Cohen	179/1.
3444323	May, 1969	Nagashima et al.	179/1.

Other Refs: Other References: Simple Digitally-Controlled Variable-Gain Linear D.C. Amplifier, by Sedra et al., Electronic Engineering, Mar. 1969, pp. 362-365.