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ASYNC SHM-NPR
2. Introduction
2.1 Description
The Async SHM-NPR is used for local data
distribution, connecting full- or half-duplex
asynchronous terminals to computers. A pair
of modems ensures integrity of data transmission,
over unconditioned 4-wire telephone lines, for
distances of up to 2 miles (3.2 km).
The SHM-NPR is a high-speed synchronous
modem operating at 76.8 Kbps. The async-to-sync
conversion is performed by over-sampling, allowing
for asynchronous data transmission at data rates up
to 19,200 bps. This design results in a unit that is
insensitive to polarity of wiring (no need to observe
“+” and “-” on the twisted pairs), and is therefore
simple to install and maintain.
