Black Box SHM-NPR Series Manuale utente
MARCH 1997
ME6100A-F
ME6100A-M
ME6101A-F
ME6101A-M
ME6102A-F
ME6102A-M
Async SHM-NPR
CUSTOMER SUPPORT INFORMATION
Order toll-free in the U.S. 24 hours, 7 A.M. Monday to midnight Friday: 877-877-BBOX
FREE technical support, 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746
Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Async
SHM-NPR
3
ASYNC SHM-NPR
TRADEMARKS
All applied-for and registered trademarks are the property
of their respective owners.
4
ASYNC SHM-NPR
CONTENTS
1. Specifications . . . . . . . . . . . . . . . . . . . . . . .5
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . .7
2.1 Description . . . . . . . . . . . . . . . . . . . . .7
2.2 Features . . . . . . . . . . . . . . . . . . . . . . .9
3. Installation . . . . . . . . . . . . . . . . . . . . . . . . .10
5
ASYNC SHM-NPR
1. Specifications
Transmission Mode — Asynchronous, full or
half duplex
Transmission Line — 4-wire unconditioned
telephone line (two twisted pairs)
Data Rates — Up to 19,200 bps
Transmission Level — -6 dBm
Transmission Controls — DCD (Circuit 109) turns
on after recognizing the receive signal from the
line; CTS (Circuit 106) turns on 1 or 12 msec
(selectable) after the terminal raises RTS
(Circuit 105)
NOTE
To ensure proper operation, the equipment connected to
the SHM-NPR should provide at least one of the following
signals: RTS (Circuit 105) or DTR (Circuit 108.2).
Transmission Range — 2 miles (3.2 km) on 24 AWG
wire at all speeds up to 19,200
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ASYNC SHM-NPR
Terminal Interface — EIA RS-232C/CCITT V.24,
integral 25-pin connector, choice of male or
female
Telephone Line Interface — 5-screw (4-wire and
ground) connector block with cable strain relief
inside plastic cover
Temperature — 32 to 122 °F (0 to 50 °C)
Humidity — Up to 95%, non-condensing
Power — None required, uses ultra-low power from
the EIA RS-232/CCITT V.24 data and control
signals
Size — 0.9”H x 2.1”W x 4.3”D (2.2 x 5.3 x 11 cm)
Weight — 3.3 oz. (90 g)
7
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.
8
ASYNC SHM-NPR
The SHM-NPR features a DCE/DTE switch. This
allows it to operate as a DTE in order to connect to
another DCE, such as a multiplexor port, without
requiring a cross cable. The carrier can be strapped
for either continuous operation (point-to-point
applications) or for switched operation, controlled
by the RTS signal (multi-point applications). Delay
between RTS and CTS is strap-selectable to 1 or
12 msec.
The low transmit level minimizes crosstalk onto
adjacent circuits within the same cable. Data is
transmitted and received at a balanced impedance,
ensuring excellent immunity to circuit noise.
Additionally, the SHM-NPR is coupled to the
telephone line through isolation transformers
which, in conjunction with electronic circuitry,
protect against AC or DC overvoltages.
Innovative circuitry design allows the SHM-NPR
to operate without connection to the main supply,
by using ultra-low power from the standard EIA
RS-232/ITU V.24 data and control signals. To ensure
proper operation, the equipment connected to the
SHM-NPR should provide at least one of the
following signals: RTS (Circuit 105) or DTR
(Circuit 108.2).
9
ASYNC SHM-NPR
2.2 Features
• Insensitive to wire polarity
• Asynchronous transmission
• Up to 19,200 bps
• Full- or half-duplex
• Point-to-point or multipoint
• Transmission range of up to 2 miles (3.2 km)
• DCE/DTE switch
• Strain relief for line cable
• Lightning-protected
• No AC power required
• Easy to install
• Compact, lightweight
10
ASYNC SHM-NPR
3. Installation
Installation of the Async SHM-NPR is simple
and straightforward. Follow these steps:
1. Separate the two parts of the plastic cover by
pressing the marked places on the side, starting
at the cable end.
2. Connect 4-wire telephone line to the screw
terminal block: transmit pair to “XMT” and
receive pair to “RCV.” To connect the cable
shield, a ground is provided.
3. Strap the modem according to the strapping
diagram (Figure 3-1) and the strap-selection
table (Table 3-1).
4. To close the unit, simply press the two halves
of the cover together.
5. Plug the modem directly into the 25-pin
connector of the terminal or computer port,
and fasten with the screws on each side of the
connector.
11
ASYNC SHM-NPR
Table 3-1. Strap Selection.
Strap/Switch Identity Function Position Factory Setting
DCE/DTE Selects SHM-NPR DCE DCE
interface DTE
Carrier Selects carrier On On
constantly on or
switched by RTS Controlled
RTS/CTS Selects RTS/CTS 1 msec 1 msec
Delay delay 12 msec
Figure 3-1. Strapping Diagram.
CARRIER
RTS/CTS DELAY
1 MS 12 MS
DTE
DCE
DCE/DTE
SWITCH
ON CONTROLLED
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