Black Box SHM-NPR, Руководство пользователя

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CHAPTER 2: Introduction
2. Introduction
Built using the latest surface-mount technology, the SHM-NPR and SHM-NPR/RJ
nonpowered short-haul modems attain high-quality performance in a low-profile
package. The units operate full-duplex at data rates up to 19.2 Kbps over two
twisted pairs (four wires). They require no AC power or batteries, but can support
distances up to 17 miles (27.3 km; see
Appendix B ).
The SHM-NPR and SHM-NPR/RJ have an external DCE/DTE switch, so you can
connect them to any type of RS-232 device without opening their chassis. And you
can terminate the line between pairs of these units in either of two ways: The SHM-
NPR models have a five-screw terminal block for hard-wired lines, and the SHM-
NPR/RJ models have modular RJ-12 (“6-wire RJ-11”) jacks. The specially designed
strain relief on the ME721 models prevents thin twisted pairs from breaking or
pulling loose.
Figure 2-1. The SHM-NPR illustrated.
DCE DTE
RS-232 device-side
interface (DB25 male
on ME721A-M units,
DB25 female on
ME721A-F units)
DCE/DTE switch
Balanced line-side
interface (five-position
terminal block)