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CHAPTER 2: Introduction
2. Introduction
2.1 Description
The Nonpowered Short Haul Modem—2-Wire (SHM-
NPR for short) connects asynchronous terminals to
computers for local data distribution. What makes this
model unique is its ability to operate in full-duplex
mode over a
single
pair of wires. In many cases, you
should be able to use the 2-wire telephone line already
installed in your building.
You can plug the SHM-NPR directly into the back of
your terminal—there’s no need for an extra cable. Two
models are available:
• ME738A-F (DB25 female connector)
• ME738A-M (DB25 male connector)
Both models also have a 2-screw terminal block.
You don’t need any power supply for the SHM-NPR,
either. Its innovative circuitry takes ultra-low power from
the standard RS-232 data and control lines. Even if only
the Transmit Data (Pin 2), Receive Data (Pin 3), and
