This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by BC548. The relay must have 100 mA of maximum current.
This circuit was obtained in a 1982 publication. There are many types of car alarms available to...
This circuit has its frequency controlled by a 1MHz crystal. The circuit must be powered by a...
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...