Data Terminal Equipment DTE refers to user equipment that convert Data Circuit-terminating Equipment DCE refers to the network equipment Data Switching Equipment DSE refers to network equipment used to Simplex. This is a unidirectional connection, i.e.,

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2.1. Equipment

This section briefly describes general networking equipment types and the types of connections that can be established between them.

2.1.1. Equipment Types

Network equipment may be classified into three broad categories:

1. Data Terminal Equipment DTE refers to user equipment that convert

outgoing user data into a transmission signal, and convert back the incoming signal into user data. DTEs may take many different shapes and forms. Examples include: terminals, terminal adapters, personal computers, and mainframes. DTEs commonly reside at user sites.

2. Data Circuit-terminating Equipment DCE refers to the network equipment

that connect DTEs to the network communication lines. In general, a DTE and a network line may use different types of signals e.g., electrical versus optical. The necessary signal conversion between these two is performed by the DCE. A DCE may be a part of a DTE or be an entirely separate device. Modems and multiplexers are all examples of DCEs.

3. Data Switching Equipment DSE refers to network equipment used to

connect DCEs together, thus providing switching capability to the network. DSEs correspond to the nodes in a network, and are responsible for routing data across the network. A DSE is commonly referred to as a switch. Digital telephone switches used in digital networks are examples. Figure 2.9 illustrates the way DTEs, DCEs, and DSEs are connected in a network. Figure 2.9 Network equipment types. DSE DTE DTE DCE DCE DCE DCE

2.1.2. Connection Types

Connections between devices may be classified into three categories: 20 Communication Networks Copyright © 2005 PragSoft

1. Simplex. This is a unidirectional connection, i.e., data can only travel in one

direction. Simplex connections are useful in situations where a device only receives or only sends data e.g., a printer.

2. Half-duplex. This is a bidirectional connection, with the restriction that data can

travel in one direction at a time.

3. Full-duplex. This is a bidirectional connection in which data can travel in both