Found in ancient American documentation this circuit uses semiconductors from the thyristor family such as SCRs, Triacs and unijunctions. The circuit can control loads up to 550 W with the indicated triacs.
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...