This circuit was obtained from Dutch documentation from 1967. It uses transistors of the time which can be the BFY50 and 51 for the output and the BC series for the others.
This circuit is recommended for alarm systems since it has a good output stage. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...