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Data Transmission


Serial Data Transmission

Serial transmission is where data is transmitted one bit at a time between devices. On wired networks data is sent along a single wire.

Serial Transmission Examples

  • USB Devices
  • Ethernet Cable Networks



Parallel Data Transmission

Parallel transmission is where multiple wires are used to transmit multiple bits of data at the same time. Once the data is received it is reassembled into the correct order at the receiving end.


Parallel  Transmission Examples

  • Parallel Printers
  • Parallel ATA Drives

Serial vs Parallel

Disadvantages of parallel

Although it is theoretically faster to transmit data using parallel transmission rather than serial, parallel has a couple of serious drawbacks.

Problem 1 – Data corruption

We data is transmitted using parallel transmission the data needs to be reassembled at the receiving end. If there any delays in transmission then the data will be reassembled in the wrong order. This problem increases in severity and likelihood as the distance between devices increases. This means that parallel transmission is only suitable for very short distances of up to a couple of metres.

Problem 2 – Cost

Parrallel wires cost more than serial wires due to the higher number of wires involved.

In order to avoid these problems most modern devices communicate using serial transmission. In order to increase data transmission rates, data is sent me closely together using devices with higher clock speeds and transmission accuracy.

Serial Supremacy

Modern serial devices can now transmit data incredibly quickly:

  • Ethernet cables : theoretical max – 1 Gbps
  • USB: theoretical max – 10Gbps




Simplex Data Transmission

Simplex data transmission is where data is only sent in one direction.

Simplex Transmission Examples

  • Radio broadcasts
  • Television broadcasts
  • Television remote controls
  • Older PS2 Keyboards / Mice



Half Duplex

Half Duplex Data Transmission

Half duplex is where data is sent both ways but data is only sent in one direction at a time.

Half Duplex Transmission Examples

  • Wifi Routers
  • Walkies Talkies
  • Parallel Printers

Full Duplex

Duplex / Full Duplex Data Transmission

Full duplex is where data is sent in both directions at the same time. If using wired transmission then 2 separate wires are used, one for sending and one for receiving. In fiber optic networks it is possible to send data along a single wire in both directions at the same time.


Full Duplex Transmission Examples

  • Ethernet
  • Fiber Optic cables