BT30 drawbar

Hi guys,
What is the most common design of the drawbar for a 45degree BT30 pullstud?
I mean the part that actually grabs the holder and pulls it up/into the
spindle. I imagine some kind of tapered "thingy" with balls that, when
pulled up, pushes the balls in making contact with the chamfer on the
pullstud. When the drawbar is pressed down the same 45deg chamfer can push
the balls backout and the holder is free to "fall out".

I've searched the net but can only find info on the pullstud and nothing on
its mating part. Does anyone have a photo, drawing, sketch or description of
how this is supposed to made?

Thanks in adavance!

/Henrik Olsson.