Toshiba PCX260 - Manual (Page 8)

8
Overview
The modem provides you with high-speed data communications over the television
cable network by following the widely accepted DOCSIS standards that were
developed by Cable Television Laboratories, Inc. This standard offer a combination of
high performance and interoperability among many of the cable system operators in
North America.
How does a cable modem work?
As you know, digital signals are represented by high and low electrical voltage le vels.
And how fast these levels can switch and still be transmitted is determined by the
"bandwidth" of the transmission system. The pair of wires used in a telephone
connection have greatly limited bandwidth, because of their electrical characteristics.
So what we do is connect a device called a modem between the computer output and
the phone line. The modem generates an electrical wave whose strength and phase
change in step with the highs and lows of the computer's digital output. It's because of
the "smoothness" of the resultant signal that a higher data rate can be transmitted.
A cable modem MOdulates and DEModulates electrical signals in the same sense that
the telephone modem does. However, since coaxial cable can carry much higher
wave frequencies, cable modems are far more sophisticated. Their internals can
include a tuner, a bridge, a router, an encryption/decryption device, an SNMP agent,
USB port and an Ethernet hub. Furthermore, none of the activity caused by these
circuits and codes disturbs yo ur regular cable TV reception.
How does a cable modem connect to a computer?
The Ethernet connection and USB connection used in this Cable Modem are
emerging as the most popular means of connecting a Cable Modem.
The new DOCSIS standard may change this in the future. But for now, an Ethernet or
USB must be ready in your computer for the Cable Modem to work.