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.
Like the previous circuit, this is used in the analog part of the telephone lines. The same...
This analog TV circuit generates bars in the NTSC standard. We found it in the July 1991 issue of...
This transmitter kicks in when the microphone picks up sound. This sound then modulates the signal...