Data Transmission | Computer for GCSE/IGCSE - Year 11 PDF Download

Wired connections

• Serial: One bit is sent at a time across a single wire

• Parallel
  • Multiple bits are sent concurrently across multiple wires during parallel transmission.
  • Asynchronous transmission may result in varying arrival times for different bits, causing skewing or skewed data.
  • This transmission method does not guarantee that all data will arrive simultaneously.

Types of Data Transmission

• Simplex: Simplex transmissions are unidirectional, traveling in only one direction.
• Half-duplex: These transmissions are bidirectional, meaning they can travel in both directions, but not simultaneously.
• Full-duplex: In full-duplex transmissions, signals can be transmitted in both directions at the same time.

Wires can be combinations of serial, parallel, simplex, half-duplex, and full-duplex transmission types.
Figure 3: Wire types can be combined between serial/parallel and simplex/half-duplex/full-duplex

Wire Types in Data Transmission

• Serial-Simplex: Data is transmitted one bit at a time in a single direction on one wire.
• Serial-Half-duplex: Data can be transmitted in both directions on a single wire, but only one bit at a time can be transmitted in one direction at a time.
• Serial-Full-duplex: Data can be transmitted in both directions at the same time on a single wire, one bit at a time.
• Parallel-Simplex: Multiple wires transmit one bit at a time in one direction.
• Parallel-Half-duplex: Multiple wires send multiple bits of data in both directions, but only one direction at a time.
• Parallel-Full-duplex: Multiple wires send multiple bits of data in both directions at the same time.

Advantages and disadvantages of each method

Understanding Data Transmission Methods

• Serial Data Transmission
  • Connecting an external hard drive to a computer
  • Transmitting data over a telephone line
• Parallel Data Transmission
  • Transmitting data from a computer to a printer using a multi-wire connector
• Simplex Data Transmission
  • Transmitting data from a computer to a printer without requiring data back from the printer
  • Modern devices like printers may send acknowledgement signals, possibly needing half-duplex connections
• Half-Duplex Communication
  • Instances where only one party can speak at a time, like in phone conversations
  • Example: A walkie-talkie with a push-to-speak button
• Full-Duplex Communication
  • Simultaneous two-way communication where both parties can speak and listen at the same time
  • Example: Broadband internet connections for downloading and uploading data