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  # 82310 14-Aug-2007 10:58
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The filters (technically filters as splitters have a 2 socket point for phone and dsl when used from the same wallplate, or at the demarc) are there to BLOCK dsl signal from normal phones.


Not wanting to be picky, but this is not strickly true. Yes one of the functions of the filter is to remove DSL energy from getting to phones (POTS devices) but the primary function is to create a impedance transformation such that any POTS device does not load the line in the DSL band. That is why DSL filters always have a sereies inductance to the line side. There are several performance parameters that a filter must meet, outof band attenuation on the POTS pass is one critical one, Loading of the ADSL band is another which is typically required to be less than 0.25dB. This means that you can create a short on the POTS side of the filter and it will have less than a 0.25dB reduction in the ADSL band energy at the input of the filter. Most POTS devices, ie phones faxs etc have a very low impedance in the band above round 20kHz, this is to prevent RF interference, if it was not for the ADSL filter this would kill the DSL signal.

Cyril

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  # 82311 14-Aug-2007 10:59
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AFAIK current "filters" also have DSL and phone sockets.

 
 
 
 


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  # 82315 14-Aug-2007 11:16
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cyril7:
The filters (technically filters as splitters have a 2 socket point for phone and dsl when used from the same wallplate, or at the demarc) are there to BLOCK dsl signal from normal phones.


Not wanting to be picky, but this is not strickly true. Yes one of the functions of the filter is to remove DSL energy from getting to phones (POTS devices) but the primary function is to create a impedance transformation such that any POTS device does not load the line in the DSL band. That is why DSL filters always have a sereies inductance to the line side. There are several performance parameters that a filter must meet, outof band attenuation on the POTS pass is one critical one, Loading of the ADSL band is another which is typically required to be less than 0.25dB. This means that you can create a short on the POTS side of the filter and it will have less than a 0.25dB reduction in the ADSL band energy at the input of the filter. Most POTS devices, ie phones faxs etc have a very low impedance in the band above round 20kHz, this is to prevent RF interference, if it was not for the ADSL filter this would kill the DSL signal.


Not picky at all, I was just rounding it up in non-geek terms for general consumption :)

Bung:
AFAIK current "filters" also have DSL and phone sockets.


http://www.dse.co.nz/cgi-bin/dse.storefront/46c0e6450072dcc8273fc0a87f330703/Product/View/XH8556

Not when you go the mum n dad/cheap route ala Cap in a box.

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  # 82317 14-Aug-2007 11:23
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I agree, these simpler filters are fine if your close to the exchange (<2.5km) and have only one or at most two POTS devices, beyond that I strongly recommend a proper Marque Magnetics filter, as noted on these forums previously these can be obtained over the counter to the public an MasterTrade for around $60, in this OPs situation based on the latter revelation that alls fine when no phones are across the line it would be $60 well spent if he has the simple ability to wire it in.

Cyril

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