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DTE = Data Terminal Equipment DCE = Data Communications Equipment

© 2004 Cisco Systems, Inc. All rights reserved. BCRAN v2.1—2-3

End devices, such as PCs, workstations, mainframe computers, and routers, are referred to as data terminal equipment. DTEs communicate with each other through data communications equipment such as modems, CSUs, and DSUs. (The EIA defines DCE as data communications equipment. The International Telecommunication Union-Telecommunication Standardization Sector [ITU-T, formerly known as CCITT] defines DCE as data circuit-terminating equipment.)

The EIA/TIA-232 standard defines the interface between DTE and DCE.

The end-to-end communication path between two DTEs consists of three segments (refer to the figure shown): DTE-DCE, DCE-DCE, and DCE-DTE. You must administer a set of cabling and configuration elements for each segment.

Note The EIA/TIA-232-C (formerly known as RS-232-C) standard is the most commonly used asynchronous interface for data communications in North America. The RS-232 standard was first issued in 1962, and its third revision, RS-232-C, was issued in August 1969. Although the ubiquitous D-shaped 25-pin connector (DB-25) has become the market standard for EIA/TIA-232-C interfaces, it was not specified in the original RS-232-C standard. Many EIA/TIA-232-C devices use other connectors, such as the DB-9 or RJ-11 /RJ-45 modular connectors. X.21 is a European standard that defines the DCE-DTE interface. For more information on these and other standards, refer to Cisco.com or any reliable data communications reference text.


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