Overview
One of the critical parts of setting up any router is the selection of the serial cables to connect the router to the serial devices in your network. There are so many different serial cables, with seemingly similar features, finding the correct cable can be tricky. This document guides you through the process of selecting the right serial cables for your network.
The selection of the proper serial cable involves answering three questions:
∙Is the router being connected to a data terminal equipment (DTE) or data communications equipment (DCE) device?
∙Is a male or female connector required on the cable?
∙What signaling standard does the device require?
With the answers to these questions, along with the model of your router, you can find the part number of the cable required from the tables that follow.
DTE or DCE?
Devices that communicate over a serial interface are divided into two classes: DTE and DCE. The most important difference between these types of devices is that the DCE device supplies the clock signal that paces the communications on the bus. The documentation provided with the device should indicate whether it is DTE or DCE (some devices have a jumper to select either mode). If you cannot find the information in the documentation, use the following general guidelines to help you select the proper class:
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| Selectable |
| DTE | DCE | DTE or |
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| DCE* |
| Terminals, Data Service |
|
|
Device | Unit/Channel Service |
|
|
| Unit (DSU/CSU), | Modems | Hubs, Routers |
| Multiplexors | ||
|
|
| |
|
|
|
|
Gender | Male | Female | Either |
|
* Selectable devices usually have a jumper, switch, or software command used to select DTE or DCE.
Male or Female
The gender of the connector is determined by examining the connector. If pins protrude from the base of the connector, the connector is male. If the connector has holes to accept the pins, the connector is female. Refer to the drawings to identify the connector that you need.
Signaling
A number of different standards defines the signaling over a serial cable (including EIA/TIA−232, X.21, V.35, EIA/TIA−449, EIA−530, and HSSI). Each standard defines the signals on the cable, and specifies the connector at the end of the cable. The documentation for the device being connected should indicate the signaling standard used for that device. If you cannot find the information in the documentation, use the illustrations below to select the signaling standard required. Select the connector that will mate with the connector on your device, rather than the illustration that looks like the connector on the device.
