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 incorporates a thermostat. The circuit is from Motorola's Linear Interface ICs from...
We found this circuit in a technical documentation from the 70s. The MC1555 is nothing more than...
This circuit was found in a 1967 RCA manual. The transistors are of the time. The adjustment is made to...