CIRCUIT ARRANGEMENT FOR AUTOMATICALLY ADJUSTING THE VOLUME OF AT LEAST ONE SPEAKER TO A RADIO NOISE LEVEL PRESENT FOR A LOCAL SPEAKER LOCATION FOR BROADCAST RECEIVERS, ESPECIALLY CAR RADIO

摘要

In a circuit which matches the speaker input signal in a car radio to the then-present noise level, an additional RC circuit is interconnected between the speaker input terminal and the input of the volume control element. Sudden increases in the speaker input voltage following a modulation pause which cause a high increase in the gain of the volume control circuit will counteract this gain, thereby preventing the excessive increase in speaker sound output following such a modulation pause which took place in the known circuits. Zener diodes to limit the voltage at the volume control elements in dependence upon the battery output voltage and to a value such that the output stage driving the speaker will not be overdriven are also provided.