This circuit was found on an old EDN and can be used as a shield. Optical couplers are from the era and modern equivalents can be used.
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...
This circuit divides the grid 60 Hz frequency to obtain 20 Hz to drive mechanical watches used at...
We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the...