This circuit was found in an English publication from the 70s, an article that teaches how to calculate instruments. The circuit is still current and can be built with an analog indicator of 100 uA.
We found this circuit in a 1977 radio documentation. The circuit uses TTL frequency dividers from...
In figure we have a three-phase AC motor control for voltages up to 600 V or 1200 V depending on...
The oscillator shown in the figure can generate signals up to 500 kHz and has good stability. Coil...