This circuit detects when an audio signal exceeds a certain level or even occurs due to an object falling, a door slamming or other. The circuit is from a Radio Electronics from January 1980.
Depending on the components, given in the table, this circuit can amplify signals of 100 MHz or...
Found in Ferranti's 1969 documentation this circuit has a maximum operating frequency of 7.5 MHz....
An interesting interface solution that can be provided in some cases is the one shown in the...