Data Transmission

Exam code: 2210

Written by: Ashika|Reviewed by: Caroline Carroll|Updated 2 July 2026

What is data transmission?

Data transmission is the process of transferring data from one device to another using a wired or wireless connection
Wired data transmission can be completed in two ways:
- Serial
- Parallel

Serial and parallel are methods of transmitting data (bits) from a sender to a receiver
Each method determines how many bits can be transmitted at once

A stream of bits is sent in sequence, one after the other, along a single wire
USB is an example of a wired serial connection

Multiple bits are sent simultaneously, with each bit travelling on its own separate wire
Parallel transmission is usually synchronous, using a clock signal to keep data aligned
However, bits can arrive at slightly different times due to skew (timing differences between wires)
A traditional printer cable is an example of a wired parallel connection

Transmission	Advantages	Disadvantages
Serial	Reliable over longer distance Cheaper to setup Low interference	Slow transmission speed
Parallel	Very fast transmission speed	Only used on short distances Prone to high interference

Simplex, half-duplex and full-duplex describe the direction in which data can be transmitted between a sender and receiver

Data can travel in both directions, but only one direction at a time
A printer cable which waits for the data to be received before sending back a ‘low ink’ message is an example of half-duplex transmission

Data can travel in both directions at the same time
Network cables can send and receive data at the same time and are examples of full-duplex data transmission
Full-duplex is used in local and wide area networks

Transmission	Advantages	Disadvantages
Simplex	Simple and low-cost for one-way communication	Cannot support two-way communication
Half-duplex	Cheaper than full-duplex for two-way communication	Slower due to one-direction-at-a-time
Full-duplex	Fast, supports simultaneous two-way data transfer	More expensive to implement

Wires can be combinations of serial, parallel, simplex, half-duplex and full-duplex

	Simplex	Half-duplex	Full-duplex
Serial	Serial-Simplex	Serial-Half-duplex	Serial-Full-duplex
Parallel	Parallel-Simplex	Parallel-Half-duplex	Parallel-Full-duplex

Serial-Simplex
- Data is transmitted one bit at a time in one direction only on a single wire
Serial-Half-duplex
- Data is transmitted one bit at a time, and can flow in both directions, but not at the same time
- This typically uses a single shared wire.
Serial-Full-duplex
- Data is transmitted one bit at a time in both directions simultaneously, but this requires two wires, one for each direction.
Parallel-Simplex
- Multiple bits are transmitted simultaneously in one direction only, using multiple wires
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 simultaneously