We found this circuit with duty cycle adjustment in the May 1988 Radio Electronics magazine. The source must be symmetrical, and the frequency given by R3 and C1.
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...