Crystal Pierce Oscillator (CB6149E)

This circuit uses a 100 kHz crystal, but nearby frequencies can be obtained with appropriate crystals. Components are still common today.

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Positive only switch (CB6924E)
This circuit was found in a 1965 Electronic Design. What it does is respond only to positive...
Flip-Flop Using NAND Gates (CB141E)
The simplest flip-flop can be built with two NAND gates as shown here. This is a Reset-Set [S-R]...
Coils for Battery Charges on Wearable (COM110E)
September 2016 - It can be obtained from Mouser Electronics coils for inductive battery chargers...