The sensors of this liquid alarm are formed by two pieces of wire with the ends peeled off. The relay depends on the supply voltage that can be between 3 and 12 V. The transistors can also be the BC548.
This circuit for analog video signals was found in old American documentation. The transistor...
This circuit was suggested by Motorola in 1980s documentation. The circuit employs an operational of...
This circuit is from an American cookbook from 1977. The circuit generates a voltage of...