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 is a handset receiver that picks up the signal emitted by a coil under the rug or...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...
When the AC Power line fails, the transistors in this circuit are biased to conduce the current to...