This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a loudspeaker warning system. The sensor is the ceramic capacitor C1 which acts as a transmission line.
This circuit transmits beeps to receivers tuned in a wide range of frequencies placed nearby. The...
After starting, this circuit turns off the relay in a time that depends on the 4020 pulse-count. This...
This simple circuit can use general purpose transistors and SCRs like the TIC106. The warning...