Cisco WS-X4908-10GE= Hardware Maintenance Manual - Page 37

Serial Connections, Serial Line Distance Limitations, EIA/TIA-232 Connections

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Network Connection Considerations Serial Connections When setting up your router, consider distance limitations and potential electromagnetic interference (EMI) as defined in the Electronic Industries Association's (EIA) and Telecommunications Industry Association (TIA) standards, such as EIA/TIA-232. Serial Line Distance Limitations Serial signals can travel a limited distance at any given bit rate; generally, the slower the baud rate, the greater the distance. All serial signals are subject to distance limits, beyond which a signal degrades significantly or is completely lost. Table 2-4 lists the IEEE-recommended maximum speeds and distances for each serial interface type; however, you may get good results at speeds and distances greater than those listed. For instance, the recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used. If you understand the electrical problems that might arise and can compensate for them, you can get good results with rates and distances greater than those shown. However, do so at your own risk. Table 2-4 EIA/TIA-232 Distance Rate (bps) 2400 4800 9600 19200 38400 56000 1544000 (T1) IEEE Standard Transmission Speeds and Distances Feet Meters 200 60 100 30 50 15 25 7.6 12 3.7 8.6 2.6 N/A N/A EIA/TIA-449, X.21, V.35, EIA-530 Distance Feet Meters 4100 1250 2050 625 1025 312 513 156 256 78 102 31 50 15 Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232. The recommended distance limits for EIA/TIA-449 shown in Table 2-4 are also valid for V.35, X.21, and EIA-530. However, you can get good results at distances and rates greater than those shown in Table 2-4. Typically, EIA/TIA-449 and EIA-530 support 2-Mbps rates, and V.35 can support 4-Mbps rates. EIA/TIA-232 Connections EIA/TIA-232, the most common interface standard in the United States, supports unbalanced circuits at signal speeds up to 64 Kbps. The network end of the adapter cable is a standard 25-pin D-shell connector known as a DB-25. (See Figure 2-13.) The router Console and Auxiliary ports also use EIA/TIA-232 connections; however, the serial module ports support synchronous connections, and the console and auxiliary ports support asynchronous connections. Preparing for Installation 2-15

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Preparing for Installation
2-15
Network Connection Considerations
Serial Connections
When setting up your router, consider distance limitations and potential electromagnetic
interference (EMI) as defined in the Electronic Industries Association’s (EIA) and
Telecommunications Industry Association (TIA) standards, such as EIA/TIA-232.
Serial Line Distance Limitations
Serial signals can travel a limited distance at any given bit rate; generally, the slower the baud rate,
the greater the distance. All serial signals are subject to distance limits, beyond which a signal
degrades significantly or is completely lost. Table 2-4 lists the IEEE-recommended maximum
speeds and distances for each serial interface type; however, you may get good results at speeds and
distances greater than those listed. For instance, the recommended maximum rate for V.35 is
2 Mbps, but 4 Mbps is commonly used. If you understand the electrical problems that might arise
and can compensate for them, you can get good results with rates and distances greater than those
shown. However, do so at your own risk.
Table 2-4
IEEE Standard Transmission Speeds and Distances
Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232. The
recommended distance limits for EIA/TIA-449 shown in Table 2-4 are also valid for V.35, X.21, and
EIA-530. However, you can get good results at distances and rates greater than those shown in
Table 2-4. Typically, EIA/TIA-449 and EIA-530 support 2-Mbps rates, and V.35 can support
4-Mbps rates.
EIA/TIA-232 Connections
EIA/TIA-232, the most common interface standard in the United States, supports unbalanced
circuits at signal speeds up to 64 Kbps. The network end of the adapter cable is a standard 25-pin
D-shell connector known as a DB-25. (See Figure 2-13.) The router Console and Auxiliary ports
also use EIA/TIA-232 connections; however, the serial module ports support synchronous
connections, and the console and auxiliary ports support asynchronous connections.
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)
N/A
N/A
50
15