---
title: "Define analog and digital signals"
subject: "Data Communication"
chapter: 1
key: "semester_5/data_communication:analog-digital-signal-define"
source: https://www.bctengineer.com/q/semester_5/data_communication/analog-digital-signal-define
site: BCT Engineering
---

# Define analog and digital signals

Data Communication · Chapter 1: Introduction

- Asked in: 2073 Chaitra, 2 marks
- Video: [Signals | Analog & Digital |  Data Communication | Lec-03 | Bhanu Priya](https://www.youtube.com/watch?v=6CyXtvOfm4g) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/analog-digital-signal-define
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-1

## Question

Define analog and digital signal with example.

## Short answer

An analog signal varies continuously in amplitude (e.g., voice waveform); a digital signal has discrete voltage levels representing bits, such as 0 V and 5 V in a computer.

## Answer

**Analog signal**: a signal whose amplitude varies continuously with time and can take any value in a range. Examples: the human voice picked up by a microphone, a sine wave, a temperature sensor output.

**Digital signal**: a signal that has only a limited number of discrete levels, usually two (for binary 0 and 1). Examples: the voltages (0 V and 5 V) in a computer, pulses on an Ethernet cable.

```text
Analog:   /\    /\        Digital:  _____     _____
         /  \  /  \  ...            |     |___|     |__
        /    \/    \
```

## Check yourself

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

1. An analog signal
   A. has only two levels
   B. is discrete
   C. varies continuously and takes any value in a range
   D. is always binary
   Answer: C. Examples: voice from a microphone, sine wave. (Key point: Analog)

2. A digital signal
   A. varies continuously
   B. cannot represent bits
   C. is a sine wave
   D. has a limited number of discrete levels, usually two
   Answer: D. Example: 0 V and 5 V in a computer. (Key point: Digital)

3. Which is digital?
   A. Pulses on an Ethernet cable
   B. Sine wave
   C. Microphone output
   D. Temperature sensor output
   Answer: A. Others are analog signals. (Key point: Example)

## Related in Data Communication

- [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×
- [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×
- [Compare analog and digital communication](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adigital-vs-analog-comparison) — Data Communication, chapter 1, asked 4×
- [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
- [Data representation; analog vs digital system](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Adata-representation-analog-digital) — Data Communication, chapter 1

## Related in other subjects

- [Advantages of digital over analog signals](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Adigital-over-analog-advantages) — Digital Logic, chapter 1, asked 5×
- [Analog/digital signals and digital advantages](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Adefine-analog-digital-advantages) — Digital Logic, chapter 1, asked 5×
- [Difference between analog and digital signals](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Aanalog-vs-digital-signals) — Digital Logic, chapter 1
- [Digital/analog signals, Gray and Excess-3 codes](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Adigital-analog-gray-excess3) — Digital Logic, chapter 1