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Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

disfroot
Rising Star
Posts: 236
Thanks: 11
Registered: ‎28-04-2008

Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

A techie question for the BT-aficionados 🙂
Pressac make a centralised ADSL (sic) filter box. (Pressac Part Number - 60/10705/PS9XX).
They claim it is tested to BT SIN 346 v2.2 in their spec sheet DS029.
The current version of SIN 346 available from BT appears to be v2.8.
Filters that pass BT SIN v2.1 are _not_ ADSL2+ tested , e.g. see the attached datasheet for the YCL MF608B - where, on page 3 ref 2 they claim SIN 346 v2.1 compliance, but, on page 4 Table 4.2 we see the claimed ADSL band to be 30kHz - 1104kHz - this is ADSL1 only.
I actually have one of these YCL MF608Bs - it was supplied with my ADSL2+ router, but I never used it, even under ADSL1, because I read that the Safecom SAMF-2000s were better.  I have recently had line troubles, and tried this YCL for the first time as part of my troubleshooting. Guess what, the modem wouldn't sync after 10+ attempts when I used it ! Swap back to the Safecom filter and it synched after the 2nd attempt.
So I am immediately suspicious that this Pressac NTE2000-style box may not have an ADSL2+ compliant microfilter, because they do not advertise the product as ADSL2+ and they only claim that it is tested to version 2.2 of the BT SIN.

To save me the headache of acquiring and reading the different versions of SIN 346, does anyone know OTOTH whether the spec at v2.2 made the change to specify filters that would be fully compliant with ADSL2+ ?
[edit: found http://www.btwebworld.com/sinet/history.htm ( use Google's cached version - it is down as I type). I'm even more confused now, because ADSL2+ is not mentioned in the BT revision history notes until SIN 346 version 2.6 ! e.g. from the history page's entries for SIN 346 we have
[tt]---------------------------------------------------------------------------
SIN 346 Issue 2.7 - BT ADSL Interface Description
Issue 2.7 of SIN 346 has been updated from the previous issue in order to remove explicit support for ADSL2.
Published 13/2/08
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.6 - BT ADSL Interface Description
This SIN has been updated to cover 21CN versions of ADSL, the possibility of ADSL 2 plus and CPE filters to ETSI standard TS101 952.
Published 03/02/06
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.5 - BT ADSL Interface Description
The SIN has been updated to be compatible with a new repair process for problem lines.
Published 11/8/04
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.4 BT ADSL Interface Description
This Supplier Information Note describes the interface presented at the end of an ADSL line at the end customer premises. The issue reflects the changing situation regarding the compatibility of ADSL lines and Redcare.
Published 7/11/03
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.3 - BT ADSL Interface Description
An Operations and Maintenance section has been added recommending that end-user CPE support F5 loopback. The clause on CPE approval requirements has been removed and Figure 6 amended
Published 11/8/03
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.2 - BT ADSL Interface Description
This supplier information note (SIN) describes the interface presented at the end of an ADSL line at the end customer premises. It is one of a family of SINS relating to ADSL delivered services. This issue includes editorial changes to clarify topology options and source of CPE ADSL filter specification requirements
Published 11/07/02
----------------------------------------------------------------------------[/tt]

[tt]----------------------------------------------------------------------------
SIN 346 Issue 2.1 - BT ADSL Interface Description
This supplier information note (SIN) describes the interface presented at the end of an ADSL line at the end customer premises. It is one of a family of SINS relating to ADSL delivered services. This issue includes editorial changes to clarify topology options and source of CPE ADSL filter specification requirements
Published 02/10/01
----------------------------------------------------------------------------[/tt]

[/edit]
10 REPLIES 10
disfroot
Rising Star
Posts: 236
Thanks: 11
Registered: ‎28-04-2008

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

here's another microfilter/splitter that still seems to be about in the wild - Excelsus Z-420A-UK rev E.
This one claims SIN 346 v2.4. It also only claims G 992.2 ( G.lite). It should mention G 992.5 if it is ADSL2+, shouldn't it ?
The  ADSL band used for testing is only up to 1MHz again according to the manufacturer's datasheet (attached)
The relevant parameters seem to be the On and Off-hook stopband isolation and the frequency they have measured it up to.
Is this one going to give the maximum speed with ADSL2+ ?
The current model on the PulseEng website is Z-350UK (attached). The stopband isolation on this model is specified up to 30MHz  (VDSL2)
How about people post the make and model of their microfilters and their datasheets, if available, so we can flush out which ones were designed before SIN 346 v2.6  ?
Anonymous
Not applicable

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

Manufacturer - "adsl nation"
Model - "XTE-2005"
Quote
Designed to exceed the the BT SIN 346 v2.2 guidelines for UK microfilters the XTE-2005 offers complete compatibility with BT services such as CLI (Caller ID).
The XTE-2005 is designed with a large ring capacitor to support the maximum REN (Ringer Equivalent Number) that the line is capable of REN 4. Fully compatible with ADSL, MaxDSL, ADSL 2 and ADSL 2+
itsme
Grafter
Posts: 5,924
Thanks: 3
Registered: ‎07-04-2007

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

@disfroot Have you got the schematics for the filters you are questioning? The schematics I have seen for filters is that it's the A/B pair go straight to the modem and a low pass filter is placed between the A/B pair and the phone. So in this case the adsl frequencies are immaterial.
disfroot
Rising Star
Posts: 236
Thanks: 11
Registered: ‎28-04-2008

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

@itsme
Yes, the low-pass filter is on the telephone side - there is a schematic in the YCL MF608B datasheet I attached to the first post that shows this. They must all be basically like this, but...
...the filter must stop _all_ of the ADSL2+ signal passing into your house POTS wiring. If the filter has only been tested up to ADSL1 (1.104MHz) frequencies and you apply an ADSL2+ signal to the line port, then the filter may pass the upper portion (from 1.104MHz to 2.208MHz) of the ADSL2+ spectrum into your house wiring (and back again) with less than the specified 55dB attenuation ( e.g see BT SIN 346 v2.8 sections 7.2 (e), (f) & (g)). The signal can then be reflected back to interfere with the ADSL2+ signal going to the modem - albeit at a much reduced level. Some low-pass filters keep on attenuating the signal in the stop band ; others don't.
There is also the issue of how the loading that the filter presents to the AB pair varies over the ADSL2+ band (return loss) if it has only been designed to meet the ADSL1 return loss spec (>16dB up to 1.MHz). If the return loss is too low, a portion of the ADSL2+ signal will get reflected at the microfilter back into the BT line, where it can interfere with the incoming signal and confuse the modem.

They've been thrashing this out in the Aussie forums since about 2006, it appears, because they are about 5 years ahead with their ADSL2+ Annex M deployment  Undecided
have a look at http://whirlpool.net.au/forum-replies.cfm?t=590510
disfroot
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Posts: 236
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Registered: ‎28-04-2008

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

@purleigh
thanks.
I couldn't find a spec sheet for this one, either. How many inductors does it have in the filter ? ( the cylindrical things - possibly with turns of fine red wire visible), e.g. the filter in the attached pic has 4.
Anonymous
Not applicable

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

disfroot
Rising Star
Posts: 236
Thanks: 11
Registered: ‎28-04-2008

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

@purleigh
Thanks ! It will be interesting to see if any ADSL2+ rated microfilters have fewer than 4 inductors.
Anonymous
Not applicable

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

I will let you search through these then ! - http://www.adslnation.com/support/filters.php  Wink
disfroot
Rising Star
Posts: 236
Thanks: 11
Registered: ‎28-04-2008

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

@purleigh
fantastic resource !! thanks !!
It looks like my Safecom SAMF-2000 is the same PCB layout as the AdslNation XF-1E (compare the 2 photos)  with the exception that the XF-1E appears to have a  non-polarised polyester capacitor where the Safecom has a 1uF 250V electrolytic - which will eventually dry out and give problems. The fact that they seem to use the 48v BT battery voltage to power part of the filter ( the 4 diodes are there to prevent polarity reversal problems if the A & B wires are swapped, presumably) is interesting. I'll get around to tracing out the circuit to confirm this.
Anonymous
Not applicable

Re: Microfilters: which version of BT SIN 346 compliance needed for ADSL2+ ?

While not directly relevant to the question you are asking (as they are not ADSL2 specific), the following links make interesting background reading for anyone else following this thread -
http://www.edn.com/contents/images/46414.pdf
http://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Line
http://www.epanorama.net/documents/telecom/adsl_filter.html
http://www.digikey.com/Web%20Export/Supplier%20Content/Pulse_553/PDF/Pulse_TIP102.pdf?redirected=1