Black Box MULTIPOINT LINE DRIVER - Manual (Page 3)

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Short-Haul Modem-B 2W-A (SHM-B 2W-A)
• Powered, point-to-point, 2-wire.
• A pair of these line drivers enables two RS-232 devices
to communicate at distances up to 2.3 miles (3.7 km)
at 2400 bps over 24 or 26 AWG.
• Fully supports hardware handshaking, so you get reliable
performance during every data exchange.
• Two status LEDs monitor transmit and receive lines.
• Loopback circuitry helps you detect line faults via a
front-panel button.
The SHM-B 2W-A is an asynchronous, full-duplex line driver
and receiver that requires only two wires to transmit data.
A pair of of these SHMs enables two RS-232 devices
to communicate at distances of up to 2.3 miles (3.7 km)
and at bit rates of up to 19.2 kbps, while fully supporting
hardware handshaking.
The SHM-B 2W-A operates over a two-wire metallic circuit.
Optimum performance is obtained with 22 to 26 AWG
twisted-pair telephone cable, but you can use nearly any
twisted-pair cable, with little or no performance degradation.
In addition to the transmitter and receiver circuits, the
modem includes RS-232 control-line interfaces, status monitor
LEDs, and a loopback switch.
A powered device, the SHM-B 2W-A is available in stand-
alone 115-VAC (ME755A) or 230-VAC (ME755AE) versions and
as a card version (ME755-C) for mounting in our 8- or 16-Card
Short-Haul Modem-B Rack.
Short-Haul Modem-B (SHM-B) Async
• Ideal for most any point-to-point, 4-wire, full-duplex
application.
• Equipped with a balanced loop interface and optical
isolation circuitry, providing protection from differences
in ground potential between areas.
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• Local analog loopback circuitry lets you check the
operation of both your local and remote units.
• Distances up to 4 miles (6.4 km) at 2400 bps over
24 AWG wire.
• Speeds up to 19.2 kbps.
• Standalone and card versions.
The SHM-B Async is an asynchronous, full-duplex, 4-wire
line driver/receiver that, when paired with another SHM-B
Async, enables two EIA-232 devices to communicate at
distances of up to 4 miles (at 2400 bps) over 24 AWG wire
and at data speeds of up to 19.2 kbps.
In addition to the transmitter and receiver circuits, the
SHM-B Async includes EIA-232 control line interfaces, status
monitor LEDs, and a loopback switch.
The SHM-B Async is available in five versions:
• As a standalone 115-VAC model (ME800A).
• As a standalone 115-VAC model with cables included
(ME800A-R3).
• As a standalone 230-VAC model with cables included
(ME800AE-CABPAK).
• As a rackmount card version (ME805-C).
• As a rackmount card version with cables included
(ME805C-R3).
The SHM-B is designed to operate over a 4-wire metallic
circuit, and it works best when used with twisted-pair cable.
However, you can use most types of twisted-pair cable, often
with little or no performance degradation.
It’s also designed for maximum operator safety—there are
no voltages greater than 12 VDC or 16 VAC present on the
circuit board of the unit. Receive lines are protected from
potential ground differences through optical isolators rated
at 1500 volts.
A typical application using the High-Speed SHM-B Async, a powered driver
that’s ideal for sending async data point-to-point at speeds up to 115.2 kbps.
High-Speed SHM-B Async
(ME802A)
Async minicomputer
RS-232
cable
RS-232
cable
Async
terminal
(2) twisted pairs
High-Speed SHM-B Async
(ME802A)