Network Basics: Coaxial Cable

A type of cable that was once popular for Ethernet networks is coaxial cable, sometimes called thinnet or BNC cable because of the type of connectors used on each end of the cable. Thinnet cable operates only at 10 Mbps and is rarely used for new networks. However, you’ll find plenty of existing thinnet networks still being used.

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Here are some salient points about coaxial cable:

  • You attach thinnet to the network interface card by using a goofy twist-on connector called a BNC connector. You can purchase preassembled cables with BNC connectors already attached in lengths of 25 or 50 feet, or you can buy bulk cable on a big spool and attach the connectors yourself by using a special tool. (Buy preassembled cables, attaching connectors to bulk cable can be tricky.)

  • With coaxial cables, you connect your computers point-to-point in a bus topology. At each computer, a T connector is used to connect two cables to the network interface card.

  • A special plug called a terminator is required at each end of a series of thinnet cables. The terminator prevents data from spilling out the end of the cable and staining the carpet.

  • The cables strung end-to-end from one terminator to the other are collectively called a segment. The maximum length of a thinnet segment is about 200 meters (actually, 185 meters). You can connect as many as 30 computers on one segment.

    To span a distance greater than 185 meters or to connect more than 30 computers, you must use two or more segments with a device called a repeater to connect each segment.

  • Although Ethernet coaxial cable resembles TV coaxial cable, the two types of cable aren’t interchangeable. Don’t try to cut costs by wiring your network with cheap TV cable.