This circuit from a Popular Electronics from the 90s uses a common optocoupler and a general-purpose transistor to control a sensitive relay that can be from 6 to 12 V.
This static switch circuit or solid-state contactor was found in a Motorola documentation from...
of the National Semiconductor of 1994. The same technique can be used with other operators and the...
Have you not yet memorized the color code used to identify resistors and capacitors? Do you have...