Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
This simple strobe light is from an article in 1982. Its complete circuit, very simple, appears in the...
This power step for relay activation was found in the 1964 RCA transistors manual. The circuit is of the...
This circuit, bridge type, was found in American documentation from the 60's. The transistor is...