This circuit uses a capacitor that depends on the frequency of the crystal. We found it in a 1967 documentation. The maximum frequency is around 100 kHz.
This timer was found in the Texas Instruments 1996 linear applications manual. The relay must be...
This circuit compares two light intensities, providing the indication on an analog instrument. The...
This circuit was obtained in a 1983 publication. It is a 1-transistor voltmeter, capable of...