The circuit is from 1968, but we can use a modern one like the 741. The symmetrical power supply voltage (two batteries or source) can be from 9 to 12 V.
The circuit shown in the figure below is suggested by ON Semiconductor (www.onsemi.com), based on...
This control is intended for 110 VAC or 220 VAC Motors. Any TIC series triac can be used according the power...
This circuit was found in a 1999 English magazine, but can be easily assembled with BC548...