Signal Powered Limited Distance Modem LDM70-P
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Industrial Data Communication Products > Description The LDM70 series of products is designed to allow video display terminals(VDTs) and other RS-232 devices to be connected over distances sufficient tocover any industrial or institutional complex of buildings. These modemsfeature a rugged aluminum enclosure small enough to mount on the back panel of VDT units, saving valuable desk and floor space.The LDM70 series is designed for full duplex, asynchronous operation over twoDC-continuity, non-loaded, twisted-wire pairs. Through special high-speedoptically coupled circuits, they may communicate at data rates up to 57,600 bitsper second. A handshake operation is implemented over the same two-wirepairs. A self-powered model and a host-powered model are available. The self-powered unit uses 12VAC from a wall-mounted transformer, whilethe host-powered unit takes DC power from pins 9 and 10 of the RS-232connector. The modem circuitsїand, consequently, the host deviceare protected from electrical transients due to lightning strikes or operation ofheavy industrial equipment.Each device features a convenient Data-Communication Equipment (DCE) toData-Terminal Equipment (DTE) switch which reverses pins 2 and 3 of theRS-232 connector. For installation and troubleshooting, each unit hasdiagnostic Light-Emitting Diodes (LEDs) on the transmit and receive lines. In addition, LEDs indicate valid carrier detect and data terminal ready.The RS-232 connector may be ordered as a male or female 25-pin connector.Field connection is made through a modern, solderless, screw-termination assembly. Alternatively, a convenient four-wire modular phone jack (RJ-11) isavailable. Features ?DC to 57,600bps?Complete Isolation with Optical Couplers andPower DC-to-DC Converter?Data Terminal Ready, Carrier DetectHandshake without Extra Wires?Surge Protectors?Four LED Diagnostic Indicators?Operation to 3 Miles (5km) at 9600bps,1 Mile (1.7km) at 19,200bps, 0.5 Miles (0.8km) at 57,600bps?Four-Wire Full Duplex, Two-Wire Simplex?Self-Powered or Host-Powered ?Selection of Connectors?Wide Operating Temperature Range,0 to +70װC?CE Compliant Figure 1: LDM70 Block Diagram