- 2073 Shrawan · 4+4 marks
Transmission channels; sync vs async
Short answer
Transmission channels are simplex (one-way), half-duplex (bidirectional but not simultaneously), full-duplex (simultaneous), serial or parallel. Asynchronous transmission sends characters framed by start/stop bits with gaps; synchronous transmission uses continuous blocks with sync patterns and recovered clock, providing higher efficiency and speed.
Identify and discuss different data transmission channels. How does synchronous transmission differ from asynchronous transmission?
Data transmission channels (modes)
By direction
- Simplex: one-way only; the receiver cannot reply. Example: TV broadcast, keyboard to computer.
- Half duplex: both ways, but only one at a time, using the full bandwidth in each direction. Example: walkie-talkie.
- Full duplex: both ways simultaneously, by two paths or by splitting the bandwidth. Example: telephone, Ethernet switched links.
By the number of bits sent together
- Serial: one bit at a time on one line; used for long distance.
- Parallel: n bits at a time on n lines; fast but short range.
Synchronous vs asynchronous transmission
Async: | S | 8 data bits | P | St | gap | S | data ...
Sync : | SYN SYN | data block ... | CRC | SYN |
| Point | Asynchronous | Synchronous |
|---|---|---|
| Unit sent | One character (5-8 bits) | Block/frame of many characters |
| Framing | Start and stop bits on every character | Header/trailer, sync flags per frame |
| Clock | Separate clocks, resynchronised at each start bit | Common clock, recovered from the data |
| Overhead | High (about 20-30%) | Low |
| Speed | Slow | Fast |
| Gaps | Irregular gaps allowed | Continuous stream without gaps |
| Cost | Cheap and simple | Complex and costly |
| Example | Keyboard, RS-232 | Ethernet, HDLC, leased lines |
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Multiplexing; synchronous vs asynchronous TDM · Data Communication, chapter 6 · asked 6×
- Types of data transmission technology · Data Communication, chapter 1
- Guided vs unguided transmission media · Data Communication, chapter 4
- Optical fiber vs satellite transmission · Data Communication, chapter 4
- FDM bandwidth for 10 voice channels · Data Communication, chapter 6
- Data representation; analog vs digital system · Data Communication, chapter 1
- Sync vs async; mod-12 synchronous counter · Digital Logic, chapter 8 · asked 3×
- Sync vs async; MOD-10 synchronous counter · Digital Logic, chapter 8 · asked 2×
- Sync vs async; 3-bit synchronous down counter · Digital Logic, chapter 8
- Sync vs async; 3-bit synchronous up counter (T) · Digital Logic, chapter 8