---
title: "Compare analog and digital communication"
subject: "Data Communication"
chapter: 1
key: "semester_5/data_communication:digital-vs-analog-comparison"
source: https://www.bctengineer.com/q/semester_5/data_communication/digital-vs-analog-comparison
site: BCT Engineering
---

# Compare analog and digital communication

Data Communication · Chapter 1: Introduction

- Asked in: 2076 Chaitra, 2 marks; 2074 Asoj, 6 marks; 2070 Chaitra, 5 marks; 2070 Asar, 6 marks (asked 4 times)
- Video: [Analog and Digital communication and Their Difference || Lec -02](https://www.youtube.com/watch?v=M2J37iS90_4) — Engg. & Math Insights
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/digital-vs-analog-comparison
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-1

## Question

Compare analog and digital communication systems with appropriate block diagrams.

## Short answer

Analog signals are continuous, noise accumulates, bandwidth lower, no error control, poor security, uses FDM, simple equipment. Digital signals are discrete, noise regenerated by repeaters, higher bandwidth, error detection/correction possible, strong encryption, TDM multiplexing, more complex circuitry.

## Answer

Analog systems carry information as a continuously varying signal; digital systems carry it as a sequence of discrete values (bits).

```text
Analog system:
 Source -> Modulator (AM/FM) -> Channel -> Demodulator -> User

Digital system:
 Source -> A/D (sample, quantize, encode) -> Channel encoder
        -> Line coder / modulator -> Channel (+ noise)
        -> Demodulator -> Channel decoder -> D/A -> User
```

| Point | Analog | Digital |
|---|---|---|
| Signal | Continuous in time and amplitude | Discrete levels (0 and 1) |
| Noise effect | Accumulates, cannot be removed | Regenerated by repeaters |
| Bandwidth | Less | More |
| Error control | Not possible | Detection and correction possible |
| Security | Poor | Easy encryption |
| Multiplexing | FDM | TDM (and FDM) |
| Equipment | Simple, low cost for short links | Needs ADC/DAC, more complex |
| Example | AM/FM radio, old telephone | Mobile phone, Internet, digital TV |

Digital systems are preferred today because of their noise immunity, flexibility and easy processing, even though they need more bandwidth.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does noise affect analog versus digital systems?
   A. Accumulates in analog; regenerated away in digital
   B. Accumulates in digital; removed in analog
   C. Equally in both
   D. Neither is affected
   Answer: A. Digital repeaters rebuild the pulses, while analog noise cannot be removed. (Key point: Noise effect)

2. Which needs more bandwidth?
   A. Analog
   B. Digital
   C. Both the same
   D. Neither needs bandwidth
   Answer: B. Digital transmission needs more bandwidth, a trade-off accepted for noise immunity. (Key point: Bandwidth)

3. Which block turns an analog source into bits in the digital system?
   A. Demodulator
   B. Line coder
   C. A/D converter (sample, quantize, encode)
   D. D/A converter
   Answer: C. The A/D stage samples, quantizes and encodes the signal. (Key point: Digital chain)

4. What multiplexing does the answer associate with analog and with digital systems?
   A. TDM for analog; FDM for digital
   B. FDM for both only
   C. None for either
   D. FDM for analog; TDM (and FDM) for digital
   Answer: D. Analog uses FDM; digital commonly uses TDM as well. (Key point: Multiplexing)

## Related in Data Communication

- [Advantages of digital over analog systems](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adigital-vs-analog-advantages) — Data Communication, chapter 1, asked 5×
- [Block diagram of digital communication system](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Ablock-diagram-digital-comm) — Data Communication, chapter 1, asked 8×
- [PCM and analog-to-digital conversion](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Apcm-working) — Data Communication, chapter 5, asked 4×
- [Define analog and digital signals](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aanalog-digital-signal-define) — Data Communication, chapter 1
- [Short note: Analog vs digital mux hierarchy](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aanalog-vs-digital-mux-hierarchy) — Data Communication, chapter 6
- [Digital vs analog spread spectrum](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aspread-spectrum-digital-vs-analog) — Data Communication, chapter 6

## Related in other subjects

- [Digital vs analog communication; DCS block diagram](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Adigital-vs-analog-dcs-block) — Communication Systems, chapter 1
- [Analog and digital system block diagrams; linear and non-linear distortion](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aanalog-digital-block-linear-nonlinear-distortion) — Communication Systems, chapter 1
- [Analog and digital communication systems](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aanalog-digital-comm-systems) — Instrumentation II, chapter 5
- [Analog communication block diagram; FDM of three signals](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aanalog-block-fdm-three-signals) — Communication Systems, chapter 5