Serial and parallel data transmission

Question 1

How does data transmission work?

Answer 1

Data in digital computers consist of numbers. To transmit numbers across a channel the numbers have to be converted to a physical form such as electrical currents or pulses of light. Numbers in computers are in binary (base 2) so only two physical states are required for transmission e.g. 0v and 5v.

Communication may be in guided (e.g. along a wire) or unguided (e.g. broadcast to air) channels: in both cases the data are encoded as electro-magnetic signals. Signals decrease in strength with distance and need repeating and error checking mechanisms to ensure revcovery of the data.

Question 2

What is serial data transmission?

Answer 2

• Bits are sent via an interface one bit at a time over a single wire from the source to the destination
• Everything is sent in order

Question 3

When is serial data transmission used?

Answer 3

• Fibre optics
• USB’s (universal SERIAL bus, duh)

Question 4

What is parallel data transmission?

Answer 4

• Several bits are sent simultaneously over a number of parallel wires
• More risk of bits not arriving in order, so error detection and correction is necessary

Question 5

When is parallel data transmission used?

Answer 5

• Printer using a parallel port
• Integrated Circuits (IC)

Question 6

Why would you choose serial or parallel data transmission?

Answer 6

• Long distance communication uses serial transmission because it is easier to regenerate the signal on a single line (by repeaters). It is also easier to route single lines through switches and cheaper than using multiple cables.
• Parallel transmission is confined to short distances because of the problem of skewing, the weight and expense of the cable and the difficulties of switching multiple lines through exchanges or routers.