Although the terms are most commonly used with
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,
MIL-STD-188 •
RS-232 • Certain
ITU-T standards in the V series (notably
V.24 and
V.35) • Certain
ITU-T standards in the X series (notably
X.21 and
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 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 must be used, e.g. a
null modem for RS-232 or an
Ethernet crossover cable. ==See also==