This circuit was found in a publication by Edelman from 1924. The power comes from the battery and the listening is through a high-impedance headphone.
This two-transistor circuit was found in the August 1972 issue of Radio Electronics magazine. The...
The purpose of this circuit is to automate the activation of an aquarium air pump (aerator). The...
This circuit is from the 1983 Intersil Databook. The circuit has an A / D converter for display of 4 and...