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 sensitive Japanese mid-wave receiver from the 1960s has an output power of 45 mW and is...
This circuit appeared in a Radio Electronics magazine in March 1962. The circuit uses two...
What's different about this transistorized circuit is the fact that it doesn't use a voltage...