This circuit that appears in several versions in this section and on this website was found in documentation from the 1980s. The transistors can be of any general purpose NPN type like the BC548.
This is the receiver circuit for the previous transmitter. The range of the system can reach 100...
In this game, whoever tightens the sensors, which are metal bars or spent batteries, makes the...
This circuit is from an ancient American documentation. The T-Bridge circuit determines the...