We found this transistorized circuit in a 1985 documentation. The circuit can operate with voltages from 9 to 12 V and the adjustment of the operating point or input sensitivity is done in P1.
This simple alarm circuit was found in a 1998 documentation. When the sensors are activated, the...
This circuit was found in an old American documentation. The integrated circuit used is uncommon...
Found in a 90s Electronic Design, this suggestion to have a higher voltage in a fixed regulator...