Cable Modems
A cable modem is a digital device, which connects the computer system to the Internet, via a coaxial cable, usually the same as used in a cable television network. It converts digital information into modulated RF signals(upstream) and RF signals back to digital information (downstream) across cable TV networks. Cable modem allows high-speed access to the Internet via a cable TV network. A cable modem will typically have two connections, one to the cable wall outlet and one to a computer. Most cable modems are external devices that connect to the PC through a standard 10Base-T Ethernet card and twisted-pair wiring. Cable modem speeds vary widely, depending on the cable modem system, cable network architecture, and traffic load. In the downstream direction (from the network to the computer), network speeds can be anywhere up to 27 Mbps, an aggregate amount of bandwidth that is shared by users. In the upstream direction (from computer to network), speeds can be up to 10 Mbps. However, most modem producers have selected a more optimum speed between 500 Kbps and 2.5 Mbps. An asymmetric scheme is used in most cable modems.The term ‘Cable Modem’ is quite new and refers to a modem that operates over the ordinary cable TV network cables. Basically you just connect the Cable Modem to the TV outlet for your cable TV, and the cable TV operator connects a Cable Modem Termination System (CMTS) in his end (the Head-End).
Actually the term “Cable Modem” is a bit misleading, as a Cable Modem works more like a Local Area Network (LAN) interface than as a modem.
Cable modems allow consumers access to the Internet at higher speeds and at a fraction of the time it takes traditional telephone modems.
This is true for two reasons:
1. Broadband networks make the connection up to a hundred times faster
2. The service is “always on,” meaning customers get the information they want, when they want it.
Unlike telephone modems, cable modems allow consumers to keep their telephone lines open for voice conversations.
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Electronics Engineering
