This picture shows the 4 connectors that separate the various wirings. One connector is solely for the 3-axis stepper motors with spare pins for a 4th stepper motor wiring. The 2nd connector is solely for the various limit switches, emergency stop, and spindle guard cover. The 3rd connector is for the Spindle Motor start/stop and forward/reverse. And the 4th connector is for line power supply of 220VAC (or, 110VAC if that is power supply line).