This shield circuit with an optical coupler was found in an 90s EDN. The circuit can be used with voltages from 0 to 600 V with the indicated component values.
This protector was found in an Electronics Now from the 90s. The 250 V transient suppressors are common...
Based on an LM36000 OTA this circuit was found in the July 1988 issue of Radio Electronics...
This circuit only works with incandescent lamps and the frequency is adjusted in the pot,...