What Is Data Terminal Equipment?

Data Terminal Equipment (DTE) is a terminal device that converts user information into signals or converts received signals. They can also be called tail chains. The DTE device communicates with the Data Circuit Termination Equipment (DCE). The DTE/DCE classification was introduced by IBM.

What Is Data Terminal Equipment

DTE is a functional unit of a data terminal that functions as a data source or data receiver and provides data communication control functions to be carried out according to the connection protocol.

Typically, a DTE device is a terminal (or a computer that emulates a terminal) and a DCE is a modem or other carrier-owned device. A terminal can be a single device or an interconnected subsystem of multiple devices that performs all the functions required for the user to communicate. The user interacts with the DTE or the DTE can become a user.


Two different types of devices are assumed on each end of the interconnecting cable for a case of simply adding DTE to the topology (e.g. to a hub, DCE), which also brings a less trivial case of the interconnection of devices of the same type: DTE-DTE or DCE-DCE. Such cases need crossover cables, such as for the Ethernet or null modem for RS-232.

D-sub connectors follow another rule for pin assignment.

  • 25 pin DTE devices transmit on pin 2 and receive on pin 3.
  • 25 pin DCE devices transmit on pin 3 and receive on pin 2.
  • 9 pin DTE devices transmit on pin 3 and receive on pin 2.
  • 9 pin DCE devices transmit on pin 2 and receive on pin 3.


As a general rule, a DCE device provides a clock signal (internal clocking), and a DTE device syncs to the supplied clock (external clocking).

The term is also often used in the context of Telco and Cisco equipment to refer to network devices such as terminals, PCs, but also routers and bridges that cannot or are not configured to generate clock signals.

Therefore, a direct Ethernet connection from PC to PC can also be referred to as DTE-to-DTE communication. This communication occurs via an Ethernet crossover cable, in contrast to the communication between the computer and the DCE (hub, switch, or bridge), which occurs via a straight-through Ethernet cable.

V.35 is a high-speed serial interface that supports higher data rates and connectivity between DTE (Data Terminal Equipment) or DCE (Data Transmission Equipment) over digital lines.

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