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Cisco 2010 Connected Grid Router Hardware Installation Guide
OL-31454-01
Chapter 2 Preparing for Router Installation
Network Cabling Specifications
Signaling Standards Supported
The synchronous serial ports available for the router support the following signaling standards:
EIA/TIA-232 (EIA-323). You can order a Cisco DB-25 shielded serial transition cable that has the
appropriate connector for the standard you specify. The documentation for the device should indicate the
standard used for that device. The router end of the shielded serial transition cable has a DB-25
connector, which connects to the DB-25 port on a serial grid router WAN interface card. The other end
of the serial transition cable is available with a connector appropriate for the standard you specify. For
a list of the serial cables supported for GRWICs as well as the pinouts, see “Connectors and Cabling for
the 8-Port Asynchronous/ Synchronous RS-232 GRWIC” section on page 3-33.
The synchronous serial port can be configured as DTE or DCE, depending on the attached cable.
All serial ports configured as DTE require external clocking from a CSU/DSU or other DCE device.
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.
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 Mb/s, but 4 Mb/s is commonly used.
Table 2-1 Typical DTE and DCE Devices
Device Type Gender Typical Devices
DTE Male
1
1. If pins protrude from the base of the connector, the connector is male.
Terminal
PC
DCE Female
2
2. If the connector has holes to accept pins, the connector is female.
Modem
CSU/DSU
Multiplexer
Table 2-2 Serial Signal Transmission Speeds and Distances
Distance for
EIA/TIA-232
Distance for X.21 and
V.35 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