Distance Limitations; Asynchronous/Synchronous Serial Module Baud Rates - Cisco 1841 - 3G Bundle Router Hardware Installation Manual

Preparing to Connect to a Network
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
Documentation and Submitting a Service Request" section on page
All serial ports configured as DTE require external clocking from a channel service unit/data service unit
Note
(CSU/DSU) or other DCE device.
Although we do not recommend manufacturing your own serial cables (because of the small size of the
pins on the DB-60 serial connector), cable pinouts are provided in
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 is
significantly degraded or completely lost.
Table 5-2
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 5-2
Rate (bps)
2400
4800
9600
19200
38400
56000
1544000 (T1)
Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals.
Typically, EIA/TIA-449 and EIA-530 can support a 2-Mbps rate, and V.35 can support a 4-Mbps rate.

Asynchronous/Synchronous Serial Module Baud Rates

The following baud-rate limitations apply to the slow-speed serial interfaces in the
asynchronous/synchronous serial modules:
•
•
Cisco 1800 Series Routers (Modular) Hardware Installation Guide
5-4
lists the recommended maximum speeds and distances for each serial interface type; however,
Serial Signal Transmission Speeds and Distances
Distance for
EIA/TIA-232
Feet Meters
200 60
100 30
50 15
25 7.6
12 3.7
8.6 2.6
— —
Asynchronous interface—Maximum baud rate is 115.2 kbps.
Synchronous interface—Maximum baud rate is 128 kbps, full-duplex.
Chapter 5 Cable Information and Specifications for Cisco 1800 Series Routers (Modular)
Distance for
EIA/TIA-449, X.21, V.35,
and EIA-530
Feet Meters
4100 1250
2050 625
1025 312
513 156
256 78
102 31
50 15
"Obtaining
1-15.
Cisco Modular Access Router Cable
OL-5876-03