Key Difference: Modem (short for modulator-demodulator) is a device modulates an analog carrier signal to encode and then decode digital information. A router is a device that is capable of sending and receiving data packets between computer networks, also creating an overlay network.

Modems and routers are often confused as they seem to perform the same job, connect us to the internet. However, this is wrong; as both are not responsible for connecting to the internet. When someone gets a new connection from the ISP, they are usually given a device that allows them to connect to the internet. This device is a modem. Routers are different.

Modem (short for modulator-demodulator) is a device modulates an analog carrier signal to encode and then decode digital information. The device aims to produce a signal that can easily be transmitted easily after encoding and can be easily decoded as well. Modems can be used over various means for transmitting signals such as LEDs, radio, etc. The most popular form of modems is devices that negotiate the connection between the telephone line and the ISP.

Originally modems were stand-alone devices that allowed users to connect directly to the computer using a standard RJ45. The modem was then connected with a RJ11 telephone line. Its job was then to transmit data from the telephone line to the computer resulting in an internet connection. Modems are generally classified by the amount of data they can send in a given unit of time, which is expressed in bits per second or bytes per second. Modems also play an important part in telephonic services, where it is used to transmit data from end to the other. The latest ADSL (asymmetric digital subscriber line) modems are a more recent development and are not limited to the telephone's voiceband audio frequencies. DSL modems can be used to transmit much higher frequency signals by utilizing a twisted-pair telephone cable. The new broadband modems also offer functions of a router.

Mobile broadband modems are modems that use a mobile telephone system. These modems can be embedded inside a laptop or portable system or can be connected externally. The internal systems are chips that are installed inside the portable system for wireless capability, while external systems include connect cards, USB modems, etc. These systems allow the computers to connect to the internet wirelessly using satellite connections. These are made for people who require internet during travelling.

A router is a device that is capable of sending and receiving data packets between computer networks, also creating an overlay network. The router connects two or more data line, so when a packet comes in through one line, the router reads the address information on the packet and determines the right destination, it then uses the information in its routing table or routing policy to direct the packet to the next network. On the internet, routers perform "traffic directing" functions. Routers can also be wireless as well as wired.

The most common type of routers are small office or home routers, which are responsible for passing data from the computer to the owner's cable or DSL modem, which is connected to the internet. Other routers are huge enterprise types that connect large businesses to powerful core routers that forward data to the internet. When connected in interconnected networks, the routers exchange data such as destination addresses by using a dynamic routing protocol. Each router is responsible for building up a table that lists the preferred routes between any two systems on the interconnected networks. Routers can also be used to connect two or more logical groups of computer devices known as subnets. Routers can offer multiple features such as a DHCP server, NAT, Static Routing, and Wireless Networking.

In simple terms, modems are used to connect to the internet, while routers allow wireless capabilities, the ability to connect more than one device on a single network, firewall protection, NAT, DHCP server and NAT. When getting a new internet connection, a user is usually provided with a modem that allows the user to connect to the internet. This modem can also be router or can be connected to a router to allow the user to use it on multiple networks. Modern modems usually come imbedded with routing capabilities.

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