The present invention replaces liquid crystal light control elements in fiber-optic faceplate liquid crystal displays with suspended particle devices, and provides for passive light control without the need for either polarized light or special alignment layers. The apparatus for controlling a door using a mobile radio communication system includes a transmitting device for generating control signals for unlocking the door, the door having an automatic locking device equipped with a receiving device for receiving wireless signals. The dolly is designed such that one step onto a latching or locking mechanism by the operator causes the wheel system to be forced downward relative to the stand thereby slightly lifting the power tool and stand off of the ground and enabling transport of same via the castors.