In the figure we have a circuit in which two moving bar/dot indicators are connected together to increase the number of LEDs. The circuit is from a Radio Electronics from October 1980.
This circuit, found in a 1988 documentation consisting of an audio switch that turns off the load...
This stabilized source can supply currents up to 200 mA with the indicated transistor or 500 mA...
With the shadow over the sensor, it is possible to interrupt the sound of your amplifier using this...