This circuit is from a manual from the 80's and the operational one used, uncommon nowadays, can be replaced by a modern equivalent. The power supply must be symmetrical.
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...