This circuit uses components of the time. We found it in a 1968 US documentation. The delay is 100 ns and the input impedance is 1 k.
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...