Canon C30 - Manual (Page 11)

This does not in the least bit affect the shooting.
When the shooting of the loaded cube is
completed and the next cube is replaced! it
will be automatically reset. When you .wish to
reset it to its former position half-way throughy:.
turn the cube with your hand in a reversé
direction. ‘ ■
3
After the shutter has been released;
the cube socket revolves automatically
and the next bulb is ready for flashing.
4
When the four bulbs have been flashect
the cube can be ejected by pressing
the ejector. '
* If the meter needle does not move afterithe
cube has been attached it may indicate that the
flashcube has a broken circuit.