| 1. What is a cable modem? |
| A cable modem is a small box that connects your computer to the Internet via your local cable television provider. A cable modem has two connections, one that leads to the cable lines outside your home and an Ethernet connection to your computer. A one-way cable modem will also have a telephone line connection. |
| 2. How does a cable modem work? |
| Cable modems modulate and demodulate RF signals. The cable modem receives data in what is known as the downstream signal. This signal is modulated on television channels that are six MHz wide at frequencies between 88 to 750 MHz. Using QAM 64 technology, downstream speeds can reach up to 27 MBs on the six MHz channel through which the data is transferred. This signal usually runs adjacent to other television signals.
Cable modems transmit upstream signals at frequencies between 5 and 42 MHz. This frequency range carries more noise than the downstream signal, such as noise from the home, loose connectors on the cable line, etc. All of this noise makes the upstream signal more difficult to successfully transmit. Although QPSK modulation technology makes the upstream signal more robust at this noise level, it sends data at slower speeds than the QAM 64 technology.
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| 3. What are the advantages of using a cable modem to access the Internet? |
| A cable modem will provide you with rapid download transmission speeds. Downloading a file that would take one-half hour using a telephone modem connection will take only a few minutes with a cable modem connection.
A cable modem provides a continual connection to the Internet. Two-way cable modems do not require the use of a telephone line.
Your service will not be interrupted or receive external static since the outer layer of the cable line will not allow any noise to enter the transmission line.
As a high-speed medium, you will be able to view many different multimedia presentations---"live" or streamed---such as concerts, movies, etc.
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| 4. How does a cable modem connect to a computer? |
| There are three main components that connect a cable modem to a computer: a coaxial cable, a Category 5 twisted pair line, and a 10Base-T Ethernet network interface card (also called a NIC card). The coaxial cable line from the outside of the building connects to the cable modem. The Category 5 twisted pair line connects the computer to the cable modem. The network interface card inside the computer enables the cable modem to "talk" to the computer. |
| 5. Can I watch television and browse the Internet at the same time? |
| Yes, you can. Since television and the cable modem operate on separate frequencies of the available cable bandwidth, you will be able to watch television and browse the Internet at the same time. |
| 6. How fast will a cable modem download and upload data? |
| Cable modem speeds vary depending on network architecture, your system configuration, and the number of users accessing the network at the same time. Network speeds can reach up to 27 Mbps, but speeds will also depend on the service level to which you subscribe.
The asymmetric cable modem scheme is the most common type of cable network setup, and will allow for a faster data transmission rate (higher bandwidth) on the downstream data path than the upstream data path. This network setup works well since most cable modem users download more information than they send. For example, downloading web pages and multimedia files and participating in newsgroups requires much more bandwidth than sending web page requests or email.
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| 7. Is a telephone line still required when using a cable modem to access the Internet? |
| You will not need a telephone line when using a two-way cable modem. The cable line carries both upstream and downstream signals. However, you will need a telephone line if you are using a one-way cable modem. The upstream signal travels via the telephone line to the cable office and then to the Internet. Information that you request is sent back to you via the cable line. |
| 8. How does a cable modem compare to a dialup modem? |
| Cable modems can connect to the Internet and download information much faster than a dialup modem. For example, it will take a cable modem user milliseconds to connect to the Internet while it will take a dialup modem user about a minute. Cable modems can also download information at speeds up to 500 Kbps while a dialup modem will only download information at 53 Kbps or less. |
| 9. How does a cable modem compare to xDSL? |
| Cable modems use a RF signal to carry data through your television cable wire. Since cable modem users share a single network connection to the Internet, speeds will fluctuate depending on the number of customers online at the same time.
xDSL uses the same copper wire as your copper wire telephone line to carry data, but the data is carried on a higher frequency than voice. In order for the xDSL signal to work, the copper wire must be less than 18,000 feet away from the Telephone Company's central office.
Cable modem speeds and xDSL speeds are similar, but xDSL is more expensive in most markets. |
