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 a 1990 Electronics World magazine. The circuit can be mounted today by...
The inverter circuit shown in the figure can be used to power a fluorescent lamp in an emergency...
We find this circuit in an American 1980s documentation. Modern equivalent integrated circuits can be...