ARCHIVED: What is a cable modem?

A cable modem is a device that connects a computer system to the Internet via the cable television network. Cable Internet technology allows for transfer rates as high as 30Mbps (megabits per second, or 30 million bits per second; contrast that to phone modems at 56 thousand bits per second). However, that bandwidth is commonly divided up among all subscribers in a defined area, such as a neighborhood or a subdivision. Because of this, real-world transfer rates are anywhere from 256Kbps to 4Mbps. The most common way to link to the cable modem is through an Ethernet 10BASE-T connection.

The term "cable modem" implies that it functions like a plain old telephone modem. This is not the case. A cable modem Internet connection is always on. You don't dial up anymore; just having the computer turned on is enough to be connected. Most users familiar with Ethernet should treat a computer connected through a cable modem exactly as they do one connected to an Ethernet network.

Increasingly, things are changing so that a cable modem isn't really a modem any longer; that is, it's not a device that modulates and demodulates a signal between an analog network and a digital end device. For example, a phone modem modulates a digital signal from the computer into an analog signal for the phone lines, and demodulates the analog phone signal into a digital one. The first cable modems did the same thing, except with a cable TV signal. But now, things are changing. Many cable Internet service providers (ISPs) are migrating toward a fully digital network for everything, including their television signals. This means that cable modems on those systems will no longer be modems; they will more properly be called media converters or cable terminal devices (this is the term the cable TV industry says is the proper one).

For information regarding the availability of cable modems in Bloomington, visit the Comcast web site.

For general information and an overview, visit the Cable Modem Info Center, provided by Kinetic Strategies, Inc.