We found this circuit in a Popular Electronics of the 90s. The circuit can be easily mounted today, as the components are common. The SCR can be the TIC106.
I found this circuit in a 1980 documentation, but it can be easily assembled with BC548...
We found this alarm in an English publication from 1978. Although the original power supply is 3...
Found in old documentation, this circuit can use modern equivalent components. The signal has good...