Table Of Contents
Selecting a Serial Cable
This appendix provides the following information:
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How to select a serial cable to connect your serial device
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How to Select a Serial Cable
To select a serial cable, you must answer the following questions about the serial device that you plan to connect to the router serial port:
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Note
The following sections provide information to help you answer these questions.
DTE or DCE
There are two types of devices that can communicate over a serial interface: DCE and DTE. A DCE provides a physical connection to a network and forwards traffic. A DTE connects to a network through a DCE device. Typically, a DTE device is connected to a DCE device (or vice versa) rather than another DTE device.
Check the documentation that ships with your serial device to determine if it is a DTE or DCE device. If you cannot find the information in the serial device documentation, refer to . This table summarizes serial devices that can be connected to the router serial port and whether the device is considered a DTE or DCE device. The Cisco 805 router is a DTE device by default. describes the type of cable needed to connect a DTE or DCE device to your router.
Table A-1 DTE and DCE Devices
Modems (asynchronous and synchronous)
X
Channel service unit/data service unit (CSU/DSU)
X
Multiplexers
X
Terminals
X
Routers
X
Hubs
X
Switches
X
Access server
X
1 These serial devices usually have a jumper, switch, or software command that selects the DTE or DCE mode.
Table A-2 Cable Type Needed to Connect Serial Devices
DTE
DCE
DCE
DTE
Signaling Standards
Several standards define the signaling over the serial connectors on the router and serial device, the serial cable, and the cable connectors. You can connect a serial device with the following types of connectors to the router serial port:
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Check the documentation that ships with your serial device to determine the type of serial connector on your serial device.
Connector Gender
If pins protrude from the base of a connector, the connector is male. If the connector has holes to accept the pins, the connector is female.
A DTE device typically has a male connector, while a DCE device typically has a female connector.
Examine the serial connector on your serial device to determine its gender.
Serial Connection Example
shows a typical serial connection for the Cisco 805 router. In this example, the router, which is a DTE device, is connected to a CSU/DSU or modem, which are DCE devices.
Figure A-1 Serial Connection Example
The CSU/DSU or modem and its serial connector have the following characteristics:
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Because the serial devices are DCE, you should use a DTE cable to connect the router and the CSU/DSU or modem. (For more information on the cable type needed to connect a serial device, refer to .)
Given these characteristics, the appropriate serial cable to connect the router and the CSU/DSU or modem is a DTE V.35 male cable.
Note
Serial Cable Part Numbers
summarizes serial cables that you can order from Cisco.
