This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
The circuit is suitable for calls in a residence and was published in the Radio Electronics...
This 25 W phase photo control was found in a 1965 General Electric publication. The circuit uses a...
The integrated circuit in question is an adjustable high voltage regulator from Texas Instruments...