2-9
Cisco 1900 Series Hardware Installation
OL-19084-02
Chapter 2 Preparing for Router Installation
Preparing to Connect to a Network
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 the
Cisco Modular Access Router
Cable Specifications
.
Transmission Speeds and 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 is completely lost.
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.
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:
•
Asynchronous interface—Maximum baud rate is 115.2 kbps.
•
Synchronous interface—Maximum baud rate is 128 kbps, full-duplex.
ISDN BRI Connections
The BRI WICs provide Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI)
connections. BRI WICs are available with either an S/T interface that requires an external Network
Termination 1 (NT1), or a U interface that has a built-in NT1. You can install the BRI WICs in any
available WIC slots in the chassis.
Table 2-2
Serial Signal Transmission Speeds and Distances
Distance for
EIA/TIA-232
Distance for
EIA/TIA-449, X.21, V.35,
and EIA-530
Distance for USB
Rate (bps)
Feet
Meters
Feet
Meters
Feet
Meters
2400
200
60
4100
1250
16.4
5
4800
100
30
2050
625
16.4
5
9600
50
15
1025
312
16.4
5
19200
25
7.6
513
156
16.4
5
38400
12
3.7
256
78
16.4
5
56000
8.6
2.6
102
31
16.4
5
1544000 (T1)
—
—
50
15
16.4
5
