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 1 A circuit was found in a Philips documentation from 1966. The transistor is of the time,...
We found this circuit in a Popular Electronics of the 90s. The circuit can also be used as a seat...
This two-digit timer was found in the 1983 Special Projects issue of Radio Electronics magazine. The...