Exterior 100Base-T Fast Ethernet Port - Cisco 1240 Hardware Installation Manual

Preparing for Network Connections
D E C . 2 0 1 1 — E F T R E V I E W D R A F T — C I S C O C O N F I D E N T I A L
Serial DTE or DCE Devices
A device that communicates over a synchronous serial interface is either a DCE or DTE device. A DCE
device provides a clock signal that paces the communications between the device and the router. A DTE
device does not provide a clock signal. DTE devices usually connect to DCE devices. The
documentation that accompanied the device should indicate whether it is a DTE or DCE device. (Some
devices have a jumper to select either DTE or DCE mode.)
Table 3-1
Device Type
DTE
DCE
1. If pins protrude from the base of the connector, the connector is male.
2. If the connector has holes to accept pins, the connector is female.
Signaling Standards Supported
The synchronous serial ports available for the router support the EIA/TIA-232 (EIA-323) signaling
standard. 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.
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 Channel Service Unit/Data Service
Unit (CSU/DSU) or other DCE device.

Exterior 100BASE-T Fast Ethernet Port

The router exterior Ethernet connector is compliant with Open DeviceNet Vendor Association (ODVA)
standards. Cables used with this port must also be ODVA-compliant. ODVA compliant cables and
connectors meet IP 67 ratings.
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 3-2
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 Mb/s, but 4 Mb/s is commonly used.
Cisco 1240 Connected Grid Router Hardware Installation Guide
3-6
Typical DTE and DCE Devices
Gender
1
Male
2
Female
lists the recommended maximum speeds and distances for each serial interface type; however,
Chapter 3
Table 3-1
Typical Devices
Terminal
PC
Modem
CSU/DSU
Multiplexer
Installation Safety and Site Preparation
lists typical DTE and DCE devices.
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