With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
Only one LED is turned on when S1 and S2 are pressed. The LED that will be on is just the...
This circuit is based on one of the first germanium transistors. The power comes from a solar cell...
This circuit was found in an American 80's circuit board. The components used are current except the...