Methods of Transmission
1. Direction of Data Transmission
Data can be sent in different directions depending on the hardware and requirements of the system.
Data travels in one direction only.
Data travels in both directions, but not at the same time.
Data travels in both directions simultaneously.
2. Serial vs. Parallel Transmission
This refers to how the bits are sent physically across wires.
| Method | Description | Advantages | Disadvantages |
|---|---|---|---|
| Serial | Data is sent one bit at a time over a single wire. | Cheaper cabling; Works over long distances; Less chance of data "skewing". | Slower transmission rate than parallel. |
| Parallel | Multiple bits (usually 1 byte) are sent simultaneously over multiple wires. | Very fast; High data transfer rate. | Expensive (many wires); Bits can become "skewed" (out of sync) over long distances. |
Skewing Explained
In Parallel transmission, bits can arrive at slightly different times due to tiny differences in wire properties. Over long distances, the byte becomes unreadable. This is why parallel is only used for short distances (e.g., inside a computer's motherboard or to a nearby printer via older cables).
3. Integrated Universal Serial Bus (USB)
USB is the most common modern example of Serial Transmission. When you plug in a USB device, it uses 4 wires (two for data, one for power, one for ground).
- Benefits: Devices are automatically detected; It's impossible to plug it in the wrong way (with USB-C); Backward compatible.
- Drawbacks: Cable length is limited (usually under 5 meters for high speed); Maximum transmission rate is less than internal parallel buses.
4. Summary Checklist for Exams
When asked to choose a method, remember:
- Long Distance? Use Serial.
- Internal/Short Distance/High Speed? Use Parallel.
- Real-time Video Call? Use Full-Duplex.