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Cisco MWR 1941-DC Mobile Wireless Edge Router Hardware Installation Guide
78-15827-06B0
Chapter 2 Preparing to Install the Router
Preparing to Connect to a Network
Signaling Standards Supported
The synchronous serial ports available for the router support the following signaling standards:
EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA-530. You can order a Cisco DB-60 shielded serial
transition cable that has the appropriate connector for the standard you specify. The documentation for
the device you want to connect should indicate the standard used for that device. The router end of the
shielded serial transition cable has a DB-60 connector, which connects to the DB-60 port on a serial
WAN interface card. The other end of the serial transition cable is available with a connector appropriate
for the standard you specify.
The synchronous serial port can be configured as DTE or DCE, depending on the attached cable (except
EIA-530, which is DTE only). To order a shielded cable, contact customer service. See the
“Obtaining
Technical Assistance” section on page xiii
.
Note
All serial ports configured as DTE require external clocking from a CSU/DSU or other DCE device.
Although manufacturing your own serial cables is not recommended (because of the small size of the
pins on the DB-60 serial connector), cable pinouts are provided in
Appendix B, “Cable Specifications.”
Distance Limitations
Serial signals can travel a limited distance at any given bit rate; generally, the slower the data rate, the
greater the distance. All serial signals are subject to distance limits, beyond which a signal significantly
degrades or is completely lost.
Note
Only the serial WAN interface card supports bit rates above 128 Kbps.
Table 2-2
lists the recommended maximum speeds and distances for each serial interface type; however,
you might get good results at speeds and distances greater than those listed, if you understand the
electrical problems that might arise and can compensate for them. For instance, the recommended
maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used.
Table 2-2
Serial Signal Transmission Speeds and Distances
EIA/TIA-232
Distance
EIA/TIA-449, X.21, V.35,
EIA-530 Distance
Rate (bps)
Feet
Meters
Feet
Meters
2400
200
60
4100
1250
4800
100
30
2050
625
9600
50
15
1025
312
19200
25
7.6
513
156
38400
12
3.7
256
78
56000
8.6
2.6
102
31
1544000 (T1)
—
—
50
15
