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 analog volt-ammeter was found in an Electronics World of 1968. It makes use of a 0-1 mA...
This is one of the many possible siren configurations for the 555 integrated circuit. We found it in...
This circuit was found in an Electronics World magazine from 1990. The circuit can be mounted...