A thermostat is the temperature controlling device

A device for controlling the flow of liquid can sometimes be a pipe.

It means when you are controlling the device for e.g. phone, computer, printer and etc.

a device for controlling the rate of working of machinery or for controlling fluid flow, in particular a handle controlling the supply of steam to the cylinders of a steam engine.

contactor is a controlling device unlike CB-protecting device. It is usually connected in series with the fuse.