This circuit uses three inverters to generate a rectangular signal whose frequency depends on R1 and C1. The circuit is from a March 1996 Electronics Now.
This decoder TTL circuit for 15-channel remote control was found in Selezione Radio, Italian...
This is the circuit of a sensitive voltmeter using a difficult-to-obtain 5 uA full-scale...
This circuit compares two light intensities, providing the indication on an analog instrument. The...