We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors with another 4011. The power can be made with voltages from 6 to 12 V.
This alarm with the 555 integrated circuit is from an EDN from the 90s. The circuit directly...
Found in a General Electric documentation from the 1980s, this circuit makes use of a FET...
This circuit was suggested by Siliconix in a 1980s publication. The circuit uses components from the time...