networks

Modem

A device that converts a computer's digital signal into an analogue signal for transmission over an existing telephone line. 

Router

enables data packets to be routed between different networks. For example, it  can be used to connect a LAN to a WAN, however usually it has an internet cable plugged into it, and other cables that connect to computers on the LAN.

Hub

a hardware device that connects multiple computers or devices together; they’re mainly used to form a LAN with these devices. Its main task is to take any data packet (a group of data) that is received at its port and broadcast it to every computer in the network.

Switch

checks the data packet received and works out its destination address and sends the data to the appropriate computer only.

Bridge

a type of computer network device that connects with other LAN’s that use the same protocol.

Network Interface Card

This device is an internal device connected to the motherboard and allows a device such as a desktop PC to connect to a network.

LAN (local area network)

networks that are usually contained within a single building or small geographical location 

WAN (wide area network)

network that connects LANs over a large geographical area

WLAN (wireless local area network)

local area network accessed using radio wave connections

modem advantages

They can connect computers to networks from a long distance, operate  up to 100 Megabits* per second, they can be operate 24/7, ADSL modems allow telephone conversation and internet traffic to be proccessing at the sametime

modem disadvanatages

Modems are used just as an interface between LAN and the internet, Speed is slower than on a hub, It is expensive, a modem is not understood in the intermediate process.