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 indicated to operate from high impedance sources as piezoelectric transducers....
A quartz crystal-controlled oscillator, capable of operating up to approximately 1 MHz, can be...
This circuit is based on an old operational amplifier, having been found in documentation from the...