This circuit monitors the output of a stereo amplifier, checking the balance and balance between the channels. The circuit is from American documentation from the 70s.
This circuit fires by burning the fuse when the input voltage exceeds the value referenced by the zener....
The UAA180 integrated circuit is no longer manufactured, but if the reader finds one in a scrap...
We find this circuit in a Radio Electronics of July 1984. It consists of the traditional version of 1 A...