The gain of this step is controlled by the feedback circuit depending on the strength of the input signal. The circuit will operate with modern general-purpose transistor.
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...