A device that extends the transmission distance between terminals and computers connected via private lines or networks. Also called a "short-haul modem" or "limited-distance modem," line drivers can extend a signal that is normally limited to a few dozen or a few hundred feet up to several miles. Line drivers are used to connect POS terminals, machine tools, sensors and a myriad of other digital devices to a host computer. Speeds typically range up to 128 Kbps.