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3.5
Connecting with Dial-Up Modems
If the distance between your PC and Isolated Multi-Drop
converter is greater than 3.5 miles, you can connect them
using dial-up modems. To install the Isolated Multi-Drop
converter using dial-up modems, you need these items:
•
two dial-up modems
•
one RS-232 serial cable no more than 50 feet in length
(unless your PC's modem is directly installed in the
computer)
•
one null modem cable no more than 50 feet in length
•
a telephone line for each modem
•
one Isolated Multi-Drop converter mounting kit (if you
want to mount the converter to the switchgear panel)
If you are mounting the Isolated Multi-Drop converter to a
switchgear panel, do that first. (Refer to Appendix B for
mounting dimensions.)
Follow these steps, while referring to Figure 3.4.
1.
Connect one dial-up modem to your PC; use RS-232
serial cable unless your modem is installed directly in
the computer. (If you need help in connecting the
modems and setting their switches, refer to the
modem's manual.)
2.
Using a null modem cable, connect one dial-up modem
to the RS-232 port on the converter according to
Figure 3.5.
3.
Set the MAN/AUTO switch to AUTO, and use the
BAUD thumbwheel to set the data rate to match that of
the application software and the ACCESS devices on
the network. (In Automatic mode, the converter ignores
the setting of the DCD/RTS switch.)
RS-232 Cable
50 Ft. Maximum
PC
with
Supervisory
Software
Figure 3.4 Connecting the Converter with Dial-Up Modems
Siemens Energy & Automation, Inc.
IMPORTANT
Use a null modem cable
between the Isolated
Multi-Drop Converter
and the modem.
Modem
Modem
Null Modem Cable
50 Ft. Maximum
3
Installing the Converter
1
2
3
4
*
5
6
7
8
*
20
To
Modem
Figure 3.5 Pin Assignments for Null Modem Cable
4.
Insert the RS-485 connector(s) into the port(s) on the
front of the converter. (Refer to section 3.1 for
instructions on installing the connector on the RS-485
cable.)
5.
Plug one end of the converter's power cord into the
120 VAC connection on the converter, and plug the
other end into any 120 VAC grounded power source.
6.
Turn the converter's power switch on, and verify that
the
PWR
LED
is
"Troubleshooting" if the PWR LED is not lit.)
7.
Start your software.
22 AWG Shielded
Twisted-Pair Cable
4000 Ft. Maximum
+
SHLD
Port 4
-
+
SHLD
Port 3
-
+
SHLD
Port 2
-
+
SHLD
Port 1
-
Isolated Multi-Drop
Converter
1
2
Pins 2 and 3
3
Transposed
4
5
6
7
8
Not required
*
with converter
20
To
Isolated
Multi-Drop
Converter
lit.
(Refer
to
Section
+
Device
#1
-
RS-485
Bus
+
Device
# n
-
Up to 32 devices
To Other
RS-485
Devices
5
7
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