This circuit is from a 1968 publication. Here we have several types of resistive sensors with individual adjustments triggering a single SCR. Power depends on the type of sound device to be triggered.
This circuit was found in an American 1980s documentation. The integrated circuit used is uncommon...
The sensor for this circuit is a phototransistor. We found it in the April 1971 issue of Radio...
We found this circuit in an old Signetics documentation. The integrated circuit is of the time,...