Adsl Faq; How Does Adsl Compare To Cable Modems; What Is The Expected Throughput; What Is The Micro Filter Used For - ZyXEL Communications P-660R-T1 Support Notes

P-660 series Support Notes

ADSL FAQ

1. How does ADSL compare to Cable modems?

ADSL provides a dedicated service over a single telephone line; cable modems offer a
dedicated service over a shared media. While cable modems have greater downstream
bandwidth capabilities (up to 30 Mbps), that bandwidth is shared among all users on a
line, and will therefore vary, perhaps dramatically, as more users in a neighborhood
get online at the same time. Cable modem upstream traffic will in many cases be
slower than ADSL, either because the particular cable modem is inherently slower, or
because of rate reductions caused by contention for upstream bandwidth slots. The big
difference between ADSL and cable modems, however, is the number of lines
available to each. There are no more than 12 million homes passed today that can
support two-way cable modem transmissions, and while the figure also grows steadily,
it will not catch up with telephone lines for many years. Additionally, many of the
older cable networks are not capable of offering a return channel; consequently, such
networks will need significant upgrading before they can offer high bandwidth
services.

2. What is the expected throughput?

In our test, we can get about 1.6Mbps data rate on 15Kft using the 26AWG loop. The
shorter the loop, the better the throughput. Besides, please do not stay in menu 24.1 it
will slow down the throughput.

3. What is the micro filter used for?

Generally, the voice band uses the lower frequency ranging from 0 to 4KHz, while
ADSL data transmission uses the higher frequency. The micro filter acts as a low-pass
filter for your telephone set to ensure that ADSL transmissions do not interfere with
your voice transmissions. For the details about how to connect the micro filter please
refer to the user's manual.

4. How do I know the ADSL line is up?

You can see the DSL LED on the P-660's front panel is on when the ADSL physical
layer is up.

5. How does the P-660 work on a noisy ADSL?

Depending on the line quality, the P-660 uses "Fall Back" and "Fall Forward" to
automatically adjust the date rate.
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