AVC to adjust car radio volume - using microphone to control amplifier gain according to external noise level

摘要

The volume control has a microphone picking up external noise caused by the movement of the vehicle. The microphone output signal is converted into a gain control signal for the radio amplifier. The gain control signal may also be made dependent on the speed of the vehicle by including the output from a tachometer or engine speed detector. The control can also be used with tape cassettes and citizen's band radio. A potentiometer allows the user to set the baseline volume to the value he prefers.