This circuit is from a 1965 Electronic Design. The transistors may be general purpose and the power supply must be symmetrical.
This is one of the possible configurations using the LM139, 239 or 339 voltage comparators. The...
Have you not yet memorized the color code used to identify resistors and capacitors? Do you have...
Found in American documentation from the 90's, this circuit consists of a solid state relay with...