Network Interface Cards

The network Interface Card (NIC) provides the physical connection between the network and the computer workstation. Most NIC's are internal, with the card fitting into an expansion slot inside the computer. Some computers, such as Mac Classics, use external boxes which are attached to a serial port. Laptop computers can now be purchased with a network interface card built-in or with network cards that slip into a PCMCIA slot.

Network inteface cards are a manor factor in detrmining the speed and performance of a network.

The three most common network interface connections are Ethernet cards. LocalTalk connectors and Token Ring cards. According to a International Data Corporation study, Ethernet is the most popular, followed by Token Ring and LocalTalk.

1. Ethernet Cards - Ethernet cards are usually purchased separately from a computer, although many computers (such as th Macintosh) now include an option for a pre-installed Ethernet card. Ethernet cards contain connections for either coaxial or twisted pair cables (or both). If it is designed for coaxial cable, the connection will be a BNC. If it is designed for twisted pair, it will have RJ-45 conenction. Some Ethernet cards also contain an AUI connectors. This can be used to attach coaxial, twisted pair or fiber optics cable to an Ethernet card. When this method is used there is always an external transceiver attached to the workstation.
2. LocalTalk Connectors - LocalTalk is Apple's built-in solution for networking Macintosh computers. It utilizes a special adapter box and a cable that plugs into the printer port of a Macintosh. A major disadvantage of LocalTalk is that it is slow in comparison to Ethernet. Most Ethernet connections operate at 10 Mbps (Megabits per second). In contrast, LocalTalk operates at only 230 Kbps (or .23 Mbps).

Ethernet Cards vs. LocalTalk Connections
Ethernet	LocalTalk
Fast data transfer (10 to 100 Mbps)	Slow data transfer (.23 Mbps)
Expensive - purchased separately	Built into Macintosh computers
Requires computer slot	No computer slot necessary
Available for most computers	Works only on Macintosh computers

3. Token Ring Cards - Token Ring network cards look similar to Ethernet cards. One visible difference is the type of connector on the back end of the card. Token Ring cards generally have a nine pin DIN type connector to attach the card to the network cable.