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It interesting thd different ways I have seen for low speeds?
First on AC motors lots of poles you charge the poles for different speeds but very costly motors.

Then was just was belts and or gears.
Variable pitch belts and charge the gear Works but still gears at one was costly too but not bad.

The AC/DC motors usd a Variable transformers. This first lower cost motor setup 1 to w to 1 to 100 speed reduction?

The electronic speed control start with small motors but cost was a lot lower.

The stepper motors in Printers was big change.? In 1970's? they did not need encoders for low cost printers. If skip a a few spaces out of over a hundred thousands you not notice. Next use on low cost CNC equipment. For most part they used two phases motor.
Later I saw mini 3 phase motor but I saw first controls in 1960's but winding your own motors.
Now we know as brushless DC motors . Some maybe two phases I just have seen it .?

Some dates can earlier history on web can be do to the writer error. I know mine maybe off too.?
The 1960's is where lot changes switch from tubes to transitions?

Dave?