The machine controller cover will activate or deactivate a machine on redstone signal (depending on setting), just as if you hit it with a soft hammer.
It can also be placed on the same pipe block as a shutter, pump, or conveyor module to activate or deactivate the cover. For example, this can be used with a Shutter Module on a fluid pipe with a lever to create a valve.
The machine controller will need to be strongly powered by redstone to activate, redstone dust alone will not work. Use a comparator pointing at the controller or another source of strongly powering redstone (Redpower red alloy wire, etc) to activate it.