Sorry to be a bit off topics, but I don't know how to get there information and I know you are very skilled and you have good information about these AR7.

Where I can find the hardware differences from the annex A to the annex B configurations? On the internet I found only brochures about the AR7 and no application notes that can be usefull.

I saw two AVM routers that differ for the annex A o B standard. They seem to have differences in the dicretes and in the line coupling. Could someone confirm this?

I found few old post with similar questions but without replys.

Thank you in advance.

Livio

Not sure if you are asking about functional or technical differences. Also, this question really does not belong here, but nevermind. I only know the functional differences:

Annex A is for ADSL over POTS (plain old telephone system)
Annex B is for ADSL over ISDN

Because the cutoff frequency for the filter is different, they need different filter coils (or so I suspect), so it is not a simple matter of different firmware, but different hardware. You need either one or the other, based on whether you have a ISDN phone or not. I've only ever seen one device that supported both.

Wrong. It's only a firmware (or better say microcode) question on the client side.

Really? So all these companies keep double stock, double packaging etc, when it could be a simple firmware setting?  Being blessed with no actual knowledge, I choose to think it is *also* a firmware setting.

Not that it matters really.

can confirm from practice that modems exist that can do either, selectable through the modem setup menu.
As the frequency spectrum is different for the two (the ISDN compatible annex B must leave the lower 100 kHz available to ISDN) the filtering is different. When all filtering is done digitally, it's a microcode issue. When some filtering is done using discrete LC networks there will exist different modem hardware versions, as often the case in older adsl modems.

Thank you for yours reply also to an off-topics question.

It's true that the firmware is different, but not only the firmware. With the AVM routers, you can load the firmware for the other standard/annex and it could work if the line attenuation is low and the signal to noise rate is high.

AVM sells two models: annex A and B. I have both of them. The pcb is the same, but it is differently populated in the line coupling section. Much more complex for the Annex A, may be a higher order filter.

I don't know the AR7 family. May be it is possible to support both standards with the same hardware, but I think that there are a way to switch the external filters/discretes according to the frequency band you want to be filtered.

Is there anyone who has the application notes or the schematics of the Texas Instruments reference board?

Thank you very much for your support.

Livio