Vehicle radio or cassette player - has sound level regulator automatically adjusting sound volume as function of mean value of ambient noise

摘要

The regulator is designed to automatically control the sound volume of a radio as a function of ambient audible noise within a moving vehicle. The regulator consists of an electroluminescent diode (1) which is arranged opposite a photoresistant element (2). All electro-luminescent variations of the dioe produces a corresponding variation in the resistance of the element (2). The photoresistance element (2) is connected in series with the volume control potentiometer of automobiles radio. The electroluminescent diode (1) is in series with a microphone (5) connected between the positive and negative terminals of the vehicle battery. Also in series with the diode (1) and the microphone (5) is a resistance (R1) designed produced the required volts across the elements. In parallel with the diode (1) is a series circuit consisting of a potentiometer (P1) and a capacitor (C2). These two elements determine a time constant which enables the diode (1) to control uniquely the sound volume from the average value of ambient noise and not from instantaneous values.