This commercial earphone receiver was manufactured in the 1960s in Japan. It was powered by a 9 V battery and the transistors were made of germanium.
A ring and pendulum of stripped wires form the sensor for this alarm. Once triggered, to reset, you...
Designed for the audio track, this circuit was found in a Popular Electronics from the 90's. Other...
An interesting basic circuit for projects is shown in the figure. It consists of a digital...