This simple metronome, from 1985 documentation uses only transistors and has two settings. For voltages above 6 V, up to 12 V, replace the BC557 with a BD136.
This circuit was obtained from the Radio Electronics magazine of August 1962. It is a tandem...
This simple circuit with transistors turns on a small lamp when it gets dark. The sensor is an LDR...
This circuit with the 7400 is for testing fuses from a 7.5 to 9 V power line. The LED flashes at...