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 high input impedance circuit was found in American documentation from the 1980s. The power...
This circuit shows on the screen of an oscilloscope two signals alternately at a frequency that depends...
This circuit transmits the signal taken from a telephone line to a receiver placed nearby (up to a...