GB1108413A - Improvements in electrical limiters and related devices - Google Patents

Abstract

1,108,413. Automatic gain control. BRITISH BROADCASTING CORPORATION. 27 Feb., 1967 [17 March, 1966], No. 11817/66. Heading H3Q and H4R. An audio frequency compressor or limiter, i.e. arrangement limiting the maximum amplitude of a signal without introducing appreciable waveform distortion, comprises a control rectifier system 10 which is sufficiently rapid in action to register the crest of the shortest pulse expected in the input signal. Responsive to the rectifier system is means, i.e. shaping network 12, providing a control signal having a rate of change substantially slower than that of the shortest signal pulse, and this controls a variable gain amplifier 14, in the signal path which is fed from the signal input via a delay network 16. The arrangement is such as to prevent overshoot of short pulses beyond the limiting level, while at the same time producing a gain reduction which is sufficiently gradual as not to produce audible modulation distortion. In a modification (Fig. 3, not shown), there is interposed between the signal input and the control rectifier system a further variable gain amplifier, the gain of which is controlled directly from the rectifier system.