# Data circuit-terminating equipment

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Communications system component

Terminal adapter for X.21

Two *data stations* (*terminals*, *stations*) each comprising a DCE and a DTE, connected via a network.

A **data circuit-terminating equipment**[1] (**DCE**) is a device that sits between the [data terminal equipment](/source/Data_terminal_equipment) (DTE) and a [data transmission circuit](/source/Data_transmission_circuit). It is also called **data communication(s) equipment**[2][3][4] and **data carrier equipment**.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] Usually, the DTE device is the [terminal](/source/Terminal_(telecommunication)) (or [computer](/source/Computer)), and the DCE is a [modem](/source/Modem).

In a *data station*, the DCE performs functions such as [signal](/source/Signal) conversion, [coding](/source/Channel_coding), and line clocking and may be a part of the DTE or intermediate equipment.[3] Interfacing equipment may be required to couple the DTE into a transmission circuit or [channel](/source/Communication_channel) and from a transmission circuit or channel into the DTE.

## Usage

Although the terms are most commonly used with [RS-232](/source/RS-232), several data communication standards define different types of interfaces between a DCE and a DTE. The DCE is a device that communicates with a DTE device in these standards. Standards that use this nomenclature include:

- [Federal Standard 1037C](/source/Federal_Standard_1037C), [MIL-STD-188](/source/MIL-STD-188)

- [RS-232](/source/RS-232)

- Certain [ITU-T](/source/ITU-T) standards in the V series (notably [V.24](/source/ITU-T_V.24) and [V.35](/source/V.35_(recommendation)))

- Certain [ITU-T](/source/ITU-T) standards in the X series (notably [X.21](/source/X.21) and [X.25](/source/X.25))

A general rule is that DCE devices provide the clock signal (internal clocking) and the DTE device synchronizes on the provided clock (external clocking). [D-sub](/source/D-sub) connectors follow another rule for pin assignment. DTE devices usually transmit on pin connector number 2 and receive on pin connector number 3. DCE devices are just the opposite: pin connector number 2 receives and pin connector number 3 transmits the signals.

When two devices, that are both DTE or both DCE, must be connected together without a modem or a similar media translator between them, a [crossover cable](/source/Crossover_cable) must be used, e.g. a [null modem](/source/Null_modem) for RS-232 or an [Ethernet](/source/Ethernet) crossover cable.

## See also

- [Networking hardware](/source/Networking_hardware)

- [Network interface device](/source/Network_interface_device)

## References

1. **[^](#cite_ref-TIA_1997_232F_1-0)** *TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange*. 1997.

1. **[^](#cite_ref-EIA_1969_RS232C_2-0)** *EIA standard RS-232-C: Interface between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange*. Washington: Electronic Industries Association. Engineering Dept. 1969. [OCLC](/source/OCLC_(identifier)) [38637094](https://search.worldcat.org/oclc/38637094).

1. ^ [***a***](#cite_ref-DIN_44302_3-0) [***b***](#cite_ref-DIN_44302_3-1) *DIN 44302 Datenübertragung - Begriffe*. Vol. 8. 1966. pp. 244–246. [doi](/source/Doi_(identifier)):[10.1524/itit.1966.8.16.244](https://doi.org/10.1524%2Fitit.1966.8.16.244). {{[cite book](https://en.wikipedia.org/wiki/Template:Cite_book)}}: |periodical= ignored ([help](https://en.wikipedia.org/wiki/Help:CS1_errors#periodical_ignored))

1. **[^](#cite_ref-MIL-STD-188-100_4-0)** [MIL-STD-188-100, pg. 24, Fig 4.3-1, 1972.](https://books.google.com/books?id=Xqj6VxVvWXEC&pg=PA24)

## External links

Wikimedia Commons has media related to [DCE (Data Circuit-Terminating Equipment)](https://commons.wikimedia.org/wiki/Category:DCE_(Data_Circuit-Terminating_Equipment)).

- [Data Terminating Equipment or Data Circuit-Terminating Equipment speeds](https://www.ibm.com/support/knowledgecenter/ssw_aix_71/com.ibm.aix.networkcomm/asynch_modems_dataterm.htm), IBM

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