This circuit is from an American 80's documentation. The integrated circuit is from the time and the sensor consists of a smoke chamber measuring its transparency change.
This circuit is from 1989 documentation. The circuit is based on CMOS technology and the displays are...
This circuit was obtained from an American publication from the 80's. We can use a BD136 instead...
Found in Popular Electronics this circuit will trigger a buzzer if the ignition key is removed...