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Protects data against
crosstalk and outside
noise interference.
Point-to-point or
multipoint operation,
full- or half-duplex.
Rates up to 9600 bps.
Uses Frequency Shift
Keying modulation.
Provides highly
reliable, continuous
data transmission.
Optional modules
available for 2-wire
RS-485 and 4-wire
RS-422.
T
he Short-Haul Modem-FSK
is a private-line modem that
supports 9600-bps half- and fullduplex RS-232 operation over a
single dedicated wire pair and
across sliding contacts. The
modem uses pure Frequency Shift
Keying (FSK) modulation at high
carrier frequencies (100 kHz,
106.5 kHz to 150 kHz, 156.5 kHz).
These high frequencies make the
modem particularly immune to
crosstalk and outside noise
interference, so you get highly
reliable, continuous data
transmission over distances of
several miles in harsh industrial
environments.
Extend communications over a single pair—
even in the noisiest environments!
Key Features
SHORT-HAUL MODEM-FSK (SHM-FSK)
The modem operates in pointto-point or multipoint applications.
For multipoint applications, the
modem can be operated with
one master unit and up to eight
remote units.
The master unit (ME840A-M)
transmits at 106.5/100 kHz
(Space/Mark) and receives at
156.5/150 kHz.
The remote slave unit
(ME840A-S) transmits at 156.5/
150 kHz and receives at 106.5/
100 kHz.
Since RS-485 interfaces are
common in industrial applications,
we also offer a 2-wire RS-485
module (MD3317) and a 4-wire
RS-422 module (MD3318). Simply
plug the module into the modem’s
RS-232 connector and you’ve got
your extra connection.
The modem has several
diagnostic LEDs: Carrier Detect,
Receive Data, Transmit Data,
Loopback, and Power.
The modem interface is
DTE/DCE jumper selectable, so
it’s easy to configure to suit your
application. The default configuration for the Modem is DCE. To
change this configuration, just
move the jumpers on blocks P1
and P2 (located directly behind
the DB25 RS-232 connector on the
rear panel).
The modem also includes
jumpers for cofiguring carrier
detect, chassis ground, receiver
gain, and transmit power.
Black Box Corporation • 1000 Park Drive • Lawrence, PA 15055-1018 • Tech Support: 724-746-5500 • www.blackbox.com • e-mail: info@blackbox.com
© 2003. All rights reserved.
Black Box Corporation.
11/21/2003 #18966
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Data Format:
RS-232C (RS-485 2-wire with
optional MD3317 module, RS-422
4-wire with optional MD3318
module)
Distance (Maximum): 48,000 ft.
(14630.4 m) on single twisted pair
Operation: Full-duplex or half-
duplex controlled carrier, serial
asynchronous data
Mode: Point-to-point or multipoint
with RS-232
Modulation: Frequency shift keying
(FSK); carrier signal inductively
and capacitively isolated
Speed (Maximum): 9600 bps
Interface: DTE/DCE jumper
selectable
Connectors: (1) DB25 F for RS-232C
(RS-422 and RS-485 modules),
(1) 2-position terminal block for
carrier, (1) 2-position terminal
block for power
Operating Temperature:
32 to 140°F (0 to 60°C)
Power: 120 VAC, 60/50 Hz @
9.6 watts or 24 VDC at 10 watts
Size: 1.75"H (1U) x 7.5"W x 10.5"D
(4.4 x 19.1 x 26.7 cm)
Weight: 4.5 lb. (2 kg)
Specifications
Ordering Information
ITEM CODE
Short-Haul Modem-FSK (SHM-FSK)
Master.................................................................ME840A-M
Slave......................................................................ME840A-S
Optional Modules
2-Wire RS-485..........................................................MD3317
4-Wire RS-422 .........................................................MD3318
Recognize any of these
situations?
• You wait more than 30
minutes to get through to a
vendor’s tech support.
• The so-called “tech” can’t
help you or gives you the
wrong answer.
• You don’t have a purchase
order number and the tech
refuses to help you.
• It’s 9 p.m. and you need help,
but your vendor’s tech
support line is closed.
According to a survey by Data
Communications magazine, 90%
of network managers surveyed
say that getting the technical
support they need is extremely
important when choosing a
vendor. But even though network
managers pay anywhere from 10
to 20% of their overall purchase
price for a basic service and
support contract, the technical
support and service they receive
falls short of their expectations—
and certainly isn’t worth what
they paid.
At Black Box, we guarantee
the best value and the best
support. You can even consult
our Technical Support Experts
before you buy if you need help
selecting just the right component
for your application.
Don’t waste time and
money— call Black Box today.
Why Buy From Black Box? Exceptional V alue.Exceptional Tech Support.Period.
T
he SHM-FSK performs data
communication by converting
digital signals to modulated highfrequency sine-wave carrier
signals. These converted signals
can be transmitted across much
longer distances with greater
noise immunity on wires than
square-wave digital signals. The
digital space and mark (0 and 1)
are converted in the transmitter
to carrier signals that have two
slightly different frequencies. The
two frequencies are identified by
the receiver and reconverted to
the digital signals.
The ME840A-M and ME840AS support RS-232 point-to-point
and multipoint communications.
Optional modules support pointto-point. They send data
synchronously, and they’re
transparent to protocol and to
data rates up to 9600 baud.
Technically Speaking
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