a serial link of rs232 or rs422 enables ascii communication with the projector so that it can be controlled remotely from a pc or other controller. from a pc, connect a standard 9-wire rs232 serial cable to the rs232 in port located on the side of the projection head. or, for long-distance (]100 ft.) links with an rs422-compatible pc or controller, connect rs422 cable to the rs422 port.