This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
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...