This circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit is based on a 741 that activates a buzzer with oscillator. R5 adjusts the sensitivity.
The galena XTAL is replaced by a germanium diode in this Project. Diodes such as the 1N60 or 1N34...
This radio with selector switch tuning was found in a Popular Electronics from May 1956. Listening is...
We find this circuit in an American 1980s documentation. Modern equivalent integrated circuits can be...