When the voltage in the circuit exceeds the value set in the trimpot, the LED goes off and, if a low current buzzer is used, it rings. The circuit is from American documentation from 1999.
We found this circuit in the July 1990 issue of Radio Electronics magazine. The frequencies are...
This small amplifier, with output less than 1 W, was found in a 1960 transistor manual from...
This interesting circuit was obtained from a Poptronics of February 2001. The American magazine no...