This circuit is from an 80's Radio Electronics. It triggers a load powered by the power grid from the audio signal captured by the microphone.
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...
Found in documentation from the 1990s, this circuit supports equivalent transistors. The range is on...
We found this circuit in a 1972 RCA technical documentation. The comparator can be any type and C1...