Text 13348, 59 rader
Skriven 2005-12-13 10:47:22 av TOM WALKER (1:123/140)
Ärende: DSL, Filter or Splitter
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Splitter or Filters ?
 Separating the DSL signal from the telephone service requires either a
splitter in or near the NID or filters at each telephone device. Ideally,
the DSL service provider will install a DSL splitter module inside the NID
or in a separate enclosure next to the NID and run a new cable to the DSL
modem location. But many service providers will avoid the cost of sending a
technician to install a splitter and instead will provide filters as part
of a "self installation kit." In addition to the DSL modem or router and
the cables to connect it to the line and to your computer or LAN, these
kits include a few filters (also known as "microfilters") for your phones.
The kit may also include a few duplex adapters to so that you can use one
jack for both the DSL connection and a voice connection or one filter for
several voice connections. Of course, there will probably be an additional
charge for the filters and adapters. 

 Using filters isolates the DSL service at each individual telephone jack,
but the DSL signal is present on all the jacks. That's an additional
physical connection for each telephone device. Interference on any phone
jack may impact DSL speeds or could cause DSL to stop functioning entirely.
Because the filters are connected to the line cord for each device, their
connections are subject to damage by someone just tugging on a phone line
cord and a single damaged filter connection could result in problems with
both your DSL and telephone services. If you're willing to replace all of
your telephone jacks, there are filters available mounted in faceplates
that replace standard telephone jacks. The cost of a few of these will pay
for a splitter. Using a splitter completely isolates the DSL service from
the telephone line, so the DSL signal is not present at each telephone
jack. A splitter also limits how many connection changes are required to
complete your DSL installation and is not normally subject to incidental
physical damage. DSL signal from a splitter is much more isolated from
sources of interference, resulting in optimal DSL speeds. 

If filters are used instead of a splitter, a maximum of five or six
telephone devices with filters can be used before they begin to excessively
degrade the DSL signal. Remember that "telephone devices" include answering
machines, fax machines, and satellite/cable receivers with phone line
connections. Don't forget modems - you'll want to keep dialup as a backup
capability and may need a modem to connect to the remote access at your
office. If you're looking at this page, I'd wager you have more than six
telephone devices. Even if you can limit your installation to five or six
telephone devices, you'll probably have to buy more filters than will be
included in a self installation kit. The cost of just the additional
filters would probably pay for a splitter. 

A splitter is really a better solution because it allows you to connect the
voice side to multiple jacks, normally does a better job of separating the
data and voice bandwidth, and helps prevent cross-talk problems. A splitter
requires a different cable/pair be used for the voice and data. However, if
you use a DSL splitter, your existing inside wiring can be used for voice
with very little change and without filters at each phone. 

If you have an alarm system, installing a DSL splitter has an additional
advantage. An alarm system will require either a special filter for the
connection to the RJ 31X jack for the alarm system or a splitter to
separate the DSL service from the telephone line before it goes to the RJ
31X jack for the alarm system. A splitter is the preferred option by most
alarm system companies. 
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