This circuit was found in Signetics documentation from the 90's. The circuit performance curve is shown next to the diagram. The sensor is an NTC.
The circuit shown is a documentation on 80's tunnel diodes. The frequency depends on the delay line...
This circuit generates excellent sinusoidal signals and has the frequency adjusted by VR1 which is...
This circuit was adapted from an Italian publication that no longer exists. This is “Onda Quadra”...