This simple logic level tester was found in Radio Electronics from the 90s. The inverters are of the 4009 type and the power comes from the circuit being analyzed.
This circuit causes an LED to flash at a frequency determined by capacitor C1. The circuit can be...
This flasher or neon signal powered by batteries was found in old documentation. The transformer must...
This circuit was obtained from an ancient American documentation, but appears elsewhere in this...