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.
Other operational amplifiers can be used on this unit gain amplifier. The circuit is from the 1993...
January 2017 - Pulse Electronics ER11 transformers with high insulation can be obtained from...
This circuit was found in a 90’s Electronic Engineering. The integrated circuits are of the time...