Data Terminal Equipments 

A data terminal equipment (DTE) is a device that controls data flowing to or from a computer. It is connected to the transmission medium at the end of a telecommunication link. Here we discuss the most commonly used DTEs - modem and multiplexer

01- Modem 

A modem is an electronic device used for communication between computers through telephone lines 

The name is formed from the first three letters of the two words modulator and demodulator. 

It converts digital signals received from a computer to analog signals for telephone lines. 

It also converts the analog signals received back from telephone lines to digital signals for the computer. 

The speed of the modem determines how fast it can send and receive information through telephone lines. Speed of modem is measured in bits per second (bps). 


Multiplexing is sending multiple signals on a physical medium at the same time in the form of a single, conmplex signal and then recovering the separate signals at the receiving end. 

Multiplexing divides the physical medium into logical scgments called frequency channels. 

Multiplexer combines (multiplexes) the inputs from different sources and sends them through different channels ofa medium. 

The combined data travels over the medium simultaneously. 

At the destination, a demultiplexer separates (demultiplexes) the signal and sends them to destinations. 

                               Network Topologies

Using available media and based on certain conditions, there are different ways of interconnecting the nodes. The way in which the nodes are physically interconnected to form a network is called a Topology

1 Bus topology

Characteristics of bus topology

• Easy to install.

• Requires less cable length and hence it is cost effective. 

• Failure of a node does not affect the network. 

• Failure of cable (bus) or terminator leads to a break down of the entire network. 

• Fault diagnosis is difficult. 

• Only one node can transmit data at a time.  

2 Star topology

Characteristics of star topology 

• More efficient compared to bus topology. 

• Easy to install. • Easy to diagnose faults. 

• Easy to expand depending on the specifications of central hub/switch. 

• Failure of hub/switch leads to failure of entire network. 

• Requires more cable length compared to bus topology

.3 Ring topology

Characteristics of ring topology 

• No signal amplification is required as each node amplifies the signal. 

• Requires less cable length and hence is cost effective. 

• If one node fails, entire network will fail.

• Addition of nodes to the network is difficult.

4 Mesh topology

Characteristics of mesh topology 

• Network will not fail even if one path between the nodes fails.

• Expensive because of the extra cables needed. 

• Very complex and difficult to manage. 

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