Found in a 90s EDN, this circuit is indicated for power control through a 4-20 mA line. The circuit makes use of optical couplers of the time.
Published in an old Popular Electronics, this circuit makes use of components that are still...
Suggested for the control of photographic enlargers, this 1967 General Electric circuit uses still...
Found in old documentation, this oscillator operates with high voltage. The diode must be of the...