The low-noise amplifier shown uses a rare Raytheon operational amplifier today. The circuit can be implemented with more modern operators and the power source 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...