[plug] modem on adsl

[Arie Hol]

On 9 Mar 2005 at 11:31, Russ Pitman wrote:

> Can a normal 56k external modem be used on the phone line side of an
> adsl installation? I tried,no go, but dont know if possible or if the old
> modem has died?

ADSL works over POTS by using "Spectrum sharing" where the normal telephone services such as fax, 
voice  and serial modems use the lower frequencies and ADSL uses the higher frequencies.

You must use filters on all lines/points that use normal services - the number of lines and devices 
connected connected simultaneously can affect the quality of your ADSL service.

Telstra use the term REN which is the "ring equivalent number" they can test your line remotely - 
if the REN is greater than three - then you must install a central splitter/filter which is hard 
wired into the telephone circuit in the roof space your house.

D-link manufacture central splitters but they use RJ sockets/plugs which are illegal for use as 
hardwired solutions.

If any one is interested in technical information about splitters/filters you can read the Telstra
documents RCIT.0004 and RCIT.0006 available from :

http://www.telstra.com.au/adsl/equipmnt.htm

Most of the splitters/filters made by D-Link no longer conform to Telstra specifications according 
to the above documents - if they are already in use then it is OK but they are not acceptable for 
new installations. (See above web page).

Telstra has also made some documents available about the setup and testing of ADSL connections, 
these are in PDF  and are very technical in nature but they contain a lot of info about ADSL as 
well as some very good diagrams - I don't have the URL for these documents but if any one wants 
copies I may be able to send them as attachments off-list.

If you have more than three standard telephony devices on the one service you must install a 
"central splitter/filter" and have the ADSL bypass this splitter/filter so as not to filter out the 
high frequency needed for ADSL.

Using standard devices without filters can affect the line synchronisation of your ADSL connection.

The small plug in type splitter/filters often cause problems ( humming over the line when using the 
phone handset ) sometimes it helps to have the ADSL connected to its own point and then use the 
standard inline filters on all other phone points.

The best central splitter to buy is manufactured by C10 communications -  (Part no. C10100E)
goto : 

http://www.c10.com.au/web/Products/ADSL%20Filters/

and is sold by Pacific Datacom (as part no. DC-ADSLF-CFS) at 103-107 Edwards St. East Perth -
cost about $29.00 ex gst - but they need to be installed by a Tesltra certified telecoms 
technician. They are not generally available in W.A. and may need to be ordered.

HTH

Regards Arie
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