Some devices are connected to all others, while others are only connected to a subset.

Hybrid Topology:

A combination of two or more different topologies.
Advantages: Inherits strengths of combined topologies, flexible, scalable.
Disadvantages: Complex design and management, potentially expensive.
Example: A star network connected to a bus network.

Modem and Repeater

Modem (Modulator-Demodulator):
- Function: Converts digital signals from a computer into analog signals suitable for transmission over analog lines (like telephone lines) and vice-versa.
- Modulation: Digital to Analog (at sender).
- Demodulation: Analog to Digital (at receiver).
- Use: Connects a local network (LAN) or a single computer to a wider area network (WAN) or the Internet.
Repeater:
- Function: A network device that regenerates and retransmits signals to extend the reach of a network. It operates at the Physical Layer (OSI Layer 1).
- How it works: Receives a signal, cleans it (removes noise), amplifies it, and retransmits it to its original strength.
- Use: Overcomes cable length limitations, extends network segments.

What is a Router?

A router is a network device that forwards data packets between computer networks. It performs the "traffic directing" functions on the Internet. It operates at the Network Layer (OSI Layer 3).

Function: Determines the best path for data packets to travel from source to destination across different networks.
How it works: Uses IP addresses to make routing decisions, maintains routing tables, and connects different network segments (LAN to LAN, LAN to WAN).
Key Features:
- Connects dissimilar networks (e.g., Ethernet to Wi-Fi).
- Provides network security (firewall capabilities).
- Enables communication between different subnets.

LED, Wi-MAX, Bluetooth Architecture, Hub and Bridge

LED (Light Emitting Diode):
- A semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons.
- In Communication: Used as light sources in short-distance fiber optic communication systems due to their low cost, reliability, and ease of modulation, though less powerful and slower than laser diodes.
Wi-MAX (Worldwide Interoperability for Microwave Access):
- A wireless broadband communication standard (IEEE 802.16) designed to provide high-speed internet access over large areas (up to several kilometers).
- Features: Provides an alternative to wired broadband (DSL, cable), supports both fixed and mobile access.
- Architecture: Consists of a WiMAX base station (similar to a cellular tower) and subscriber stations (user devices).
Bluetooth Architecture:
- A short-range wireless technology standard (IEEE 802.15.1) for exchanging data between fixed and mobile devices over short distances.
- Piconet: A small, ad-hoc network formed by 2 to 8 Bluetooth devices. One device is the "master" (controls communication), and up to 7 others are "slaves". Communication is typically one-to-many.
- Scatternet: Multiple interconn