This circuit is from a 1965 General Electric hobby manual. The circuit can be assembled with sensitive reed relays.
The circuit presented emulates an OR gate with the LM3900, operational transconductance amplifier....
Found in a 90s QST magazine, this circuit uses components from that time. No information is given...
This circuit is the conventional use of the 7805 as a constant current source up to 1 A. The...