This audio circuit was published in a Rado Electronics issue from October 1963. The transistors are from the time and the output is low impedance. Power is supplied with a voltage of 12 V.
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...