Crystal Calibrator (CB21783E)

This circuit generates a 1 MHz signal for general equipment calibration. The circuit is from an American documentation from 1977.

Full cup detector (CB6956E)
This circuit was found in Popular Electronics. Its purpose is to warn the visually impaired when a glass...
Leak meter (CB8385E)
This circuit is from an American publication about old neon lamps. The circuit is leak proof and...
Gemanium Transistors Wien Bridge Oscillator (CB14768E)
The frequency of this oscillator, found in the 1960 transistor reference manual, is around 3.5...