---
title: "Define switching and multiplexing"
subject: "Computer Networks and Security"
chapter: 2
key: "semester_7/computer_networks_and_security:define-switching-multiplexing"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/define-switching-multiplexing
site: BCT Engineering
---

# Define switching and multiplexing

Computer Networks and Security · Chapter 2: Physical Layer

- Asked in: 2074 Asoj, 2 marks; 2069 Chaitra, 4 marks (asked 2 times)
- Video: [Switching Techniques in Computer Networks](https://www.youtube.com/watch?v=-HlJ4psu5aU) — Neso Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/define-switching-multiplexing
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-2

## Question

Define switching and multiplexing.

## Short answer

Switching connects input lines to correct output lines at network nodes to route data without direct links, with types circuit, packet, and message switching. Multiplexing combines multiple signals onto one shared link using FDM, TDM, or WDM to improve bandwidth use.

## Answer

#### Switching
Switching is the technique of connecting the many input lines of a network node to the correct output line so that data can travel from the source to the destination across a network without a direct link between every pair of devices. The three main types are circuit switching, packet switching and message switching.

#### Multiplexing
Multiplexing is the technique of combining several signals from many users into one signal that is carried over a single shared link (the multiplexer, MUX, combines them and the demultiplexer, DEMUX, separates them at the other end). It makes better use of bandwidth and reduces cable cost.

Types:
- **FDM** (Frequency Division Multiplexing) for analog signals: each signal gets its own frequency band.
- **TDM** (Time Division Multiplexing): each signal gets a time slot (synchronous or statistical).
- **WDM** (Wavelength Division Multiplexing): different light wavelengths over fibre.

## Check yourself

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

1. What is switching?
   A. Combining many signals into one
   B. Connecting input lines of a node to the correct output line so data can reach its destination without direct links between every pair
   C. Encrypting packets
   D. Amplifying signals
   Answer: B. Switching forwards data from input to the right output across a network. (Key point: Switching)

2. What is multiplexing?
   A. Combining several signals into one signal over a shared link, separated by a DEMUX at the other end
   B. Choosing a route
   C. Dividing a link into dedicated cables
   D. Detecting errors
   Answer: A. A MUX combines signals and a DEMUX separates them. (Key point: Multiplexing)

3. Which matches the type with its basis?
   A. FDM: time slots; TDM: frequency bands
   B. FDM: frequency bands; TDM: time slots; WDM: light wavelengths
   C. WDM: time slots
   D. FDM: wavelengths
   Answer: B. FDM uses frequency bands, TDM time slots, WDM light wavelengths over fibre. (Key point: Multiplexing types)

## Related in Computer Networks and Security

- [Switching compared with multiplexing](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aswitching-vs-multiplexing) — Computer Networks and Security, chapter 2