We found this circuit in a 1965 magazine. The circuit can be assembled with current equivalent transistors and the precision in generating the frequencies depends on the tolerance of the capacitors.
This very simple oscillator, with only one transistor, was found in a Japanese magazine in 1967....
This simple bridge circuit can be used for impedance or resistance measurement using a high...
This circuit has the intensity of the signals controlled by the light that falls on the sensor....