Auto-synchronous Motors

I've worked on some weird and wonderful motors in the past but not on auto-synchronous motors. The nearest thing I've got to them were rotary converters but they were started by pony motors. (Just the merest rumour that the duty converters had to be swapped over would clear the electrical department, no one wanted to do it! It was like an electrical firework display with you stood in the middle of it).

This is something that puzzles me. An auto-synchronous motor starts as a slip ring induction motor. As the motor approaches full speed are the slip rings shorted or is DC applied to the rings at this point? If it is surely this must give one hell of a kick on the line current as it drags it's self in to synchronisation. What is the sequence of operation at the point of synchronising?

And before anyone says it I've looked on Google but not found anything that clearly outlines the sequence.