Data terminal equipment is a piece of telecommunications or networking hardware that allows communication over a data line. There are several different items that are routinely called data terminal equipment, and they range from automatic teller machines to personal computers. In all cases, these different items are a location where information goes into or comes out of a machine. To further expand the scope of the term, some companies refer to any piece of centralized networking hardware, such as a switch or router, as data terminal equipment.

There are two important terms within data terminal equipment. Data is information; it doesn’t matter what the source, content or purpose of the information may be. A terminal is any machine that connects to a data transmission system. In the past, this was a phone line, but modern terminals may have a network, cellular or satellite connection.

The center point of a piece of data terminal equipment is the transmission of information. In most cases, these items move information from a human source to another human source via a network or phone system. For instance, a person writes a message on his computer and faxes it to another person. The computer that sent the fax and the fax machine that received it are pieces of data terminal equipment and the network and/or phone line that transferred the information is data circuit-terminating equipment.

Some companies expand the scope of data terminal equipment to encompass hardware that the information encounters while it is traveling. This definition includes routers, hubs and switches. In these cases, the information is considered at its final spot when it reaches the hardware. The hardware will process the information and send it back out; this is new information that just happens to have the exact same content as the previous transmission.

What is and isn’t a piece of data terminal equipment is often very vague. For instance, in the case of a personal computer, the entire thing is the data terminal. The keyboard, mouse and monitor are just as much a part of the terminal as the main system and network interface.

Some items, simply by virtue of how they work, are nearly always data terminal equipment. Bank-based automatic teller machines both take in and give out information and are connected to the bank that supports them. These machines do things such as verify account information and funds totals, which would be impossible without a data connection. The same goes for telephones and fax machines; without the connection to a telecommunication system, they don’t perform any type of function.