This circuit was found in a 1968 US publication. Transistors used are uncommon today. The circuit can be adapted to operate with modern equivalent components.
We found this circuit in an old publication. The circuit can be implemented with modern equivalent...
Operational amplifiers used in this 80's circuit is not very common today, but the setting can be...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...