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.
In the same way that we can regulate the voltage in the positive branch of the circuit, we can...
Based on the MC1488 or MC1489 operational amplifiers, this circuit has a 5000V isolation driving a...
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...