Found in Motorola documentation from the 90s, this circuit makes use of a triac from that time. The circuit is for the 110 V mains but can be modified for other grid voltages.
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...