The MDR-3 accepts commands from Preston Hand Units connected via the rugged G4 wireless link or Command cable, and controls up to four digital motors and camera run/stop functions for film and video cameras. Compatible with the full range of Preston digital motors, the MDR-3 automatically finds the span of the lens once each motor is plugged in, and each channel has its own three-level torque adjustment and direction switch to drive virtually any lens, no matter the conditions. The dual Serial ports allow connection to the Light Ranger 2 and other distance measurement systems such as the CineTape and Sniper. The MDR-3 transmits that distance information wirelessly to the HU4, where it is displayed in large, clear numbers. Firmware updates can be loaded through either Serial port or the mini USB port.