The LDM70 isolated RS-232 line driver is designed to allow video display terminals (VDTs) and other RS-232 devices to be connected over distances sufficient to cover any industrial or institutional complex of buildings. These limited distance modems feature a rugged aluminum enclosure small enough to mount on the back panel of VDT units, saving valuable desk and floor space.
The LDM70 line driver is designed for full duplex, asynchronous operation over two DC-continuity, non-loaded, twisted-wire pairs. Through special highspeed optically coupled circuits, they may communicate at data rates up to 57,600 baud. A handshake operation is implemented over the same two-wire pairs. A self-powered model and a host-powered model are available. The self-powered unit uses 12V AC from a wall-mounted transformer, while the host-powered unit takes ± DC power from pins 9 and 10 of the RS-232 connector. The modem circuits - and, consequently, the host device - are protected from electrical transients due to lightning strikes or operation of heavy industrial equipment.