| 摘要 |
The invention relates to a method of attenuation control for the digital signals on transmission links depending on the direction of speech transmission at hands-free stations. The originally analog signals on the transmission side are converted into digital signals for transmission and these in turn are converted into analog signals on the receiving side. As known, the conversion is performed according to a logarithmic characteristic. However, such a characteristic does not reach its zero value until infinity, so that, for example in a system of co-ordinates with attenuation values on the X axis and assigned values of bit units for the attenuation on the Y axis, attenuation values and bit assignments no longer correspond accurately enough to one another when the zero point of the system of co-ordinates is approached, and result in distortions. According to the invention, therefore, a microcomputer is provided in which, at a very high attenuation (that is, close to the zero point on the X axis), the values on the logarithmic characteristic are assigned corresponding genuine bit values and are output automatically in this characteristic region.
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