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RAD Data Communications 2006 Catalog
MINIATURE SHORT RANGE MODEMS/
MINIATURE FIBER 0PTIC MODEMS
12
MINIATURE SHORT RANGE MODEMS / MINIATURE FIBER 0PTIC MODEMS
FOM-485
Miniature RS-485 Fiber Optic Modem
The FOM-485 is an asynchronous miniature
fiber optic modem that transmits RS-485
signals over fiber optic cables. The FOM-485
is used in utility applications where there is
a need to connect the main controller to a
remote terminal unit (RTU).
The FOM-485 allows connection of up to
32 RTUs to a single host, at a wide range of
data rates up to 115.2 kbps, at typical
distances up to 40 km (25 miles) over
single mode fiber.
The FOM-485 supports full duplex
transmission over 4-wire or half duplex over
2-wire cables. It supports diagnostic
capabilities complying with the ITU V.54
standard.
The modem has six LED indicators to display
the status of the modem: TD, RD, DCD, RTS,
TEST, and ERR.
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• Converts from RS-485 to fiber
• Asynchronous transmission up to 115.2 kbps
• Transmission range up to 40 km (25 miles)
over single mode fiber
• Full duplex over 4-wire or half duplex over
2-wire
• V.54 diagnostics
• LED indicators for status display
FOM-485
RS-485
4-wire
Main
controller
Fiber
RTU
FOM-485
The SRM-3A is an ultra-miniature
asynchronous short range modem connecting
full duplex asynchronous terminals to
computers. Using 24 AWG and operating at
9.6 kbps, it has an extended range of
4.5 km/2.8 miles. It typically operates at data
rates up to 19.2 kbps.
The combination of the modem’s miniature
size and the use of a 9-pin D-type
connector makes it particularly suitable for
PCs, for connecting laptop computers to a
mainframe and for UNIX systems such as
Unisys U6000/50.
The SRM-3A is coupled to the line through
isolation transformers for protection against
AC or DC overvoltages. SRM-3A operates
without external power by drawing low
power from the DTE data and control
signals. The modem will operate fully even if
only Transmit Data is connected, i.e.,
without any control signals.
The modem connects to the DTE via a 9-pin
connector, male or female. Connection to
the line is via a 4-screw terminal block,
RJ-11 jack or RJ-45 jack.
SRM-3A
Ultra-Miniature Async Short Range Modem
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• RS-232/V.24 on 9-pin connector
• 4-wire, full duplex
• Data rates up to 19.2 kbps
• Transformer-isolated
• No external power required
• Compatible with the SRM-5A and SRM-6A
Mainframe
Laptop
computer
4-wire
SRM-3A SRM-3A
Approximate Range (for 24 AWG/0.5 mm)
Data Rate
kbps km miles
19.2 1.0 0.6
9.6 4.5 2.8
4.8 6.0 3.7
2.4 7.0 4.3
1.2 7.0 4.3
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