The sensor of this circuit found in Popular Electronics can be formed by a piece of fabric between two bare wire screens. When wet, the fabric will pass the current between the screens, triggering the alarm.
This circuit from a 1968 Motorola documentation provides a 120 AC output with 60 Hz from a 48 V DC...
This circuit from the 90s, found in an Electronic Engineering can be used as a shield since its...
This circuit split the voltage of a Power supply allowing it to be used as dual supply. The limit...