Just had a look at mine (which works): A small wheel marked Z D M / T B I.
When set to Z/T, it opens and closes using the release. Once to open, once to close.
On the D/B setting, it stays open as long as the release lever is depressed (or cable release is pressed.
Do not cock the shutter for any of these two.
On M/I setting, the "normal" timed shutter is operating. Shutter must be cocked.