From TechnoDocs
The spindle inverters are what provides power and control to high frequency spindles (typically made by HSD, Columbo, and on older machines, Perske).
Porter cable, Kress and Dewalt spindles do not have inverters.
If you are unsure of what type of spindle you have, follow the guide on Finding your spindle
What follows are common inverters over the years, listed in order of recently employed by techno:
Altivar series inverter:
Teco (may also bear the name motortronics) Model FM100 inverter:
