We found this circuit in a 1967 General Electric SCR manual. The time is set to R1 and depends on C1 which must be a low-leak capacitor.
The circuit shown has a voltage gain of 500 times and can use equivalent FETs like the BF245. The...
Found in a 1968 Novel Electronics Circuit, this circuit compares two light intensities using...
We found this circuit in an old publication from Argentina. The relay must be of the sensitive type,...