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Transmission Modes in Computer Networks

Transmission mode refers to the method of transferring data between two devices in a network. It defines the direction in which data can flow between the communicating devices. It is also known as communication modes.

There are three main transmission modes:

  1. Simplex
  2. Half-Duplex
  3. Full-Duplex

1. Simplex

Simplex mode is a one-way communication method where data flows in only one direction—from sender to receiver, with no reverse path. In this mode, the sender can only send data, and the receiver can only receive it.

Simplex mode allows data transmission in only one direction, from sender to receiver. The receiver cannot send back any data. Examples include radio and television broadcasting.

Key Features
  • One-way communication
  • No feedback from receiver
  • Simple and cost-effective
  • Used where acknowledgment is not required
Examples
  • Keyboard → Computer
  • Computer → Monitor
  • Radio broadcast (FM/AM)
  • Television broadcast
  • Speakers (audio out only)
Advantages
  • Efficient for one-direction communication
  • Low cost and easy implementation
  • No response delay
Disadvantages
  • No error correction (receiver cannot send feedback)
  • Not suitable for two-way communication

2. Half-Duplex

Half-Duplex mode allows data to flow in both directions, but not at the same time. When one device is sending, the other must wait until the communication line is free. It is two-way communication, but one direction at a time.

Half-duplex mode supports two-way communication, but only one device can send at a time. Devices take turns in sending and receiving. An example is a walkie-talkie.

Key Features
  • Two-way communication
  • Only one device can transmit at a time
  • Switching between send and receive mode
  • Suitable for systems where simultaneous communication is not required
Examples
  • Walkie-talkies
  • Police radios
  • CB radios (Citizen Band radios)
  • Older Ethernet networks
  • Communication between two stations in railway control
Advantages
  • Uses bandwidth more efficiently than simplex
  • Less costly than full-duplex systems
  • Works well in systems where replies are short
Disadvantages
  • Cannot transmit and receive at the same time
  • Slower than full-duplex
  • Causes delay due to turn-taking

3. Full-Duplex

Full-Duplex mode allows data to be transmitted in both directions at the same time. Both devices can send and receive simultaneously without waiting. It is true bi-directional communication.

Full-duplex mode allows simultaneous two-way communication. Both devices can send and receive data at the same time. Examples include mobile phones and video calls.

Key Features
  • Two-way simultaneous communication
  • No waiting or switching between send/receive
  • Provides maximum efficiency
  • Used in fast, real-time communication systems
Examples
  • Mobile phones (you talk and listen at the same time)
  • Video calls / Zoom / WhatsApp calls
  • Modern Ethernet networks
  • Telephone landlines
Advantages
  • Very fast communication
  • No delay because both can talk at once
  • Best for real-time applications (voice/video)
  • Highest bandwidth utilization
Disadvantages
  • More complex hardware is required
  • More expensive than simplex and half-duplex
  • Requires proper channel management

Transmission modes define the direction of data flow in a network. They are of three types: Simplex (one-way only), Half-Duplex (two-way but not simultaneous), and Full-Duplex (two-way simultaneous communication).

MCQ

Transmission Modes

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