What is a network card?

A network card (otherwise called an ethernet card) plugs into the computer's motherboard and provides a port for connecting to a computer network.
A computer network consists of more than one computer and peripherals connected together by cables or hubs to be able to share common information among each other. It handles the communication and network protocol for the computer.

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There are three kinds of network topologies that are supported by the network card. Ethernet, Token Ring or FDDI (Fiber Distributed Data Interface).

The card and its device drivers are the only components in the system that recognize the type of network being used. This means the type of network being used is only transparent to the application software using it.

The network card, also called a network interface card (NIC), sends and receives data to and from the system bus in parallel and sends and receives data to and from the network in series.

The card also converts the transmitted data into a signal that is appropriate for the network. Examples of this are:

• The fiber optic FDDI card has a laser diode that converts the data to light pulses for transmission.

• The twisted-pair ethernet card converts the data from the 5-volt signal to the voltage used by the twisted-pair cable. The component on the card that performs the signal conversion is called the transceiver.

  Some ethernet cards have more than one transceiver with different ports to allow for different cabling. Such a card is known as a combo card.

All the cards are manufactured with a unique address called media access control (MAC) address. This means no two cards should have the same MAC address.

Each card requires an IRQ (Interrupt Request) and an I/O (Input/Output) address.

Most present day cards are Plug and Play while older cards use jumpers or dip switches to determine which resources to request.

Conclusion

Finally, when selecting a network card, remember these important factors:

• The type of network you are connecting to (Ethernet, Token Ring or FDDI).

• The type of cable you are using (shielded twisted-pair, coaxial or fiber optic cable).

• The type of I/O (Input/Output) bus you are connecting the card to - PCI (Peripheral Component Interconnect) or ISA (Industry Standard Architecture).

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