2
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 Value. Exceptional Tech Support. Period.
T
he SHM-FSK performs data
communication by converting
digital signals to modulated high-
frequency 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 ME840A-
S support RS-232 point-to-point
and multipoint communications.
Optional modules support point-
to-point. They send data
synchronously, and they’re
transparent to protocol and to
data rates up to 9600 baud.
Technically Speaking
