We found this circuit in an English publication from 1969. The circuit uses transistors from the time and can operate at frequencies up to 300 MHz. Observe the waveforms of the obtained signal.
Found in American documentation from the 90s, this configuration detects the direction of rotation...
Circuits similar to this can be found in this section. This is from 1967 General Electric...
This circuit uses two transistors and can be powered by just two small batteries. The frequency is given...