ZyXEL Communications ADSL VoIP IAD with 802.11g Wireless 2602HW Series User Manual page 44

Prestige 2602HW Series User's Guide
As data rates increase, the carrying distance decreases. That means that users who are beyond
a certain distance from the telephone company's central office may not be able to obtain the
higher speeds.
A DSL connection is a point-to-point dedicated circuit, meaning that the link is always up and
there is no dialing required.
Introduction to ADSL
It is an asymmetrical technology, meaning that the downstream data rate is much higher than
the upstream data rate. As mentioned, this works well for a typical Internet session in which
more information is downloaded, for example, from Web servers, than is uploaded. ADSL
operates in a frequency range that is above the frequency range of voice services, so the two
systems can operate over the same cable.
44 Introduction to DSL