This circuit was found on an 80's Ham Radio. The transistor admits equivalent. The circuit can generate 20 to 100 MHz signals operating at the fifth harmonic of the crystal.
This circuit is from an old American documentation using LEDs in the rectification. The circuit...
This source only uses passive components (without transistors or integrated circuits) and even so it...
This four-digit circuit was found in a 1990 documentation. The sensor can be a contact or reed...