5-3
Cisco Network Modules Hardware Installation Guide
OL-2485-20
Chapter 5 Connecting Serial Network Modules
About Serial Connections
All serial interface types except EIA/TIA-530 and EIA/TIA-530A are available in DTE or DCE format:
DTE with a plug connector at the network end, and DCE with a receptacle at the network end. V.35 is
available in either mode, with either gender at the network end. EIA/TIA-530 and EIA/TIA-530A are
available in DTE only.
Serial cables are not provided with the network module. For ordering information, see the
“Obtaining
Technical Assistance” section on page xi
.
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 the online document
Cisco Modular
Access Router Cable Specifications.
For further information, see the
“Obtaining Documentation” section
on page viii
.
About Data Rates and Distance Limitations
All serial signals are subject to distance limits, beyond which the signal degrades significantly or is
completely lost. Generally, the slower the data rate, the greater the distance.
Table 5-3
lists recommended maximum speeds and distances for each serial interface type. If you
understand and compensate for potential electrical problems, 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.
Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. The
recommended distance limits for EIA/TIA-449 shown in
Table 5-3
are also valid for V.35, X.21, and
EIA/TIA-530. Typically, EIA/TIA-449 and EIA/TIA-530 support 2-Mbps rates, and V.35 can support
4-Mbps rates.
Asynchronous and Synchronous Serial Module Data Rates
The following data-rate limitations apply to the slow-speed serial interfaces found on asynchronous and
synchronous serial modules:
•
The maximum data rate on the slow-speed asynchronous interface is 115.2 kbps. The traffic
throughput rate allowed is the full 115.2 kbps, with 10 percent of traffic in the opposite direction.
•
The maximum data rate for the slow-speed synchronous interface is 128 kbps full duplex.
Table 5-3
Serial Interface Recommended Maximum Speeds and Distances
EIA/TIA-232 Distance
EIA/TIA-449, -530, -530A, V.35, and X.21 Distance
Data Rate, bps
Feet
Meters
Feet
Meters
2400
200
60
4100
1250
4800
100
30
2050
625
9600
50
15
1025
312
19200
25
8
500
150
38400
12
4
250
75
56000
9
3
100
30
1544000 (T1)
—
—
50
15