Network Interface Cards. Modems

Network Interface Cards. Modems.

A Network Interface Card (NIC) is a computer hardware component that connects a computer to a computer network, typically a Local Area Network (LAN). Networked computers communicate with each other using a particular protocol or agreed-upon language for transmitting data packets between the different machines or "nodes." The network interface card acts as an interpreter, allowing the machine to both send and receive data on a LAN. Information Technology (IT) specialists often use these cards to setup wired or wireless networks.

Function and Purpose of an NIC

One of the most common languages or protocols used with a LAN is Ethernet. There are also other, lesser-used protocols such as Token Ring and technology that allows an electronic device to exchange data or connect to the internet wirelessly using radio waves, called WI-FI. When building a LAN, a network interface card is installed in each computer on the network and each one must use the same architecture. For example, all the cards must be Ethernet cards, Token Ring cards, or an alternate technology.

An Ethernet network interface card is installed in an available slot inside the computer, typically on the motherboard. The NIC assigns a unique Media Access Control (MAC) address to the machine, which is used to direct traffic between the computers on a network. Network cards also change data from a parallel format, used by computers, to a serial format necessary in data transfers; and then back again for received information.

Wired Networks

A card's back plate features a port that fits a data cable, such as an Ethernet cable, which runs from each NIC to a central hub or switch. The hub acts like a relay, passing information between computers using their MAC addresses and allowing them to share resources like printers and scanners. In a wired network, a cable physically connects each computer to each other or to a hub.

Wireless Networks

A network interface card does not have to be hard-wired with physical cable. Wireless cards are installed like their wired counterparts, but rather than a port for a cable, the card features a small antenna. The NIC communicates with a central wireless switch or hub via radio waves. Wireless LANs are often convenient, but may have some restrictions depending on the material a building is made from. For example, lead in walls can block wireless signals between the network interface card and a hub or switch.

A NIC, or network interface card, allows your computer to connect to a network where all the systems are physically cabled together.  
A modem, or modulator/demodulator, serves much of the same functions as a NIC except that it changes digital computer signals to analog signals to transfer information.

The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel. These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

Integrated NIC's and Modems

Many motherboards have integrated (built-in) network cards and/or modems (although modems are becoming less common as fewer people are using dialup Internet service). The quality of these built-in adaptors range from truly horrible to quite good, depending on the quality and price range of the board.

If you select a motherboard with a built-in modem or NIC, you should be sure that there are expansion slots available for an aftermarket card, just in case the on-board device ever fails or doesn't work to your satisfaction.