Found in a Popular Electronics from the 90's, this circuit makes use of an integrated from the uncommon era today. The circuit serves as a reference.
We found this good power amplifier with the LM12 integrated circuit in the March 1989 issue of...
This simple circuit produces a tone when triggered by any vibration picked up by the sensor. The...
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...