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Computer Science IGCSEPDF 12
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● Communication protocols consider direction, method, and
synchronization.
Types of Direction
1. Simplex:
○ One-way only.
○ Example: computer → printer.
2. Half-Duplex:
○ Two-way but only one side at a time.
○ Example: walkie-talkies.
3. Full-Duplex:
○ Both directions simultaneously.
○ Example: broadband internet, phone calls.
4. Methods of Data Transmission
Serial Transmission
● Sends 1 bit at a time over a single channel/wire.
● Can be simplex, half-duplex, or full-duplex.
● Common in long-distance transmission (telephone lines, USB).
Advantages:
● Cheaper (fewer wires).
● Easier to synchronise (only one stream).
● Less interference (fewer channels).
● Reliable over long distances.
Disadvantages:
● Slower than parallel.
● Usually for smaller data transfers.
Parallel Transmission
● Sends multiple bits simultaneously (e.g., 1 byte).
● Requires multiple wires/channels.
● Often used for short distances (e.g., internal components, printer ports).