SJ/Z 9140.3-1987
Sound system equipment Part 8 Automatic gain control device (English Version)
- Standard No.
- SJ/Z 9140.3-1987
- Language
- Chinese, Available in English version
- Published By
- Professional Standard - Electron
- Latest
- SJ/Z 9140.3-1987
- Scope
- 1.1 This standard applies to automatic gain control circuits (AGC circuits) for various purposes in sound systems. 1.2 This standard covers devices that have amplitude limiting and/or compression characteristics with respect to the envelope of the input signal. a. The limiting function is mainly used as a safety measure to prevent overloading of equipment such as tape recorders, power amplifiers and transmitters. b. Compression is used to reduce the dynamic range of speech and music programs. The purpose of using compression is to match the dynamic range of the program material to the useful signal-to-noise ratio of the transmission circuit or to the difference between the allowable program sound level and the noise level of the radiating program environment. Compression is used to achieve special effects when replaying sound programs. 1.3 This standard does not cover: a. Expanders, as these devices are currently used only in highly specialized professional equipment. However, the definitions in this standard can be extended to include such devices. b. In some installations, the gain of a sound channel is controlled not by the signal fed through the channel, but by the signal from an external source. For example in a call channel the gain is varied according to the ambient noise level in the listening area or in the case of a "dubbing limiter" the gain of the music channel is reduced when the announcer speaks. Such device characteristics can be specified and measured in similar ways. c. A clipper is a nonlinear device used to cut off peaks exceeding a certain level. It is basically different from limiters and compressors that can maintain the input signal waveform when stable.
SJ/Z 9140.3-1987 history
- 1970 SJ/Z 9140.3-1987 Sound system equipment Part 8 Automatic gain control device
