[Asterisk-Users] PSTN Incoming call on real line disrupts VoIP call over DSL circuit - EXPLAINED

[Bob Chiodini]

Jürgen,

The TAE jack sounds like a great idea.  In my house all of the phone and
data cabling is home-run to a punch-down block in a "Comm closet".  The
single DSL/POTS filter is located there along with the modem router and
a SPA-3000.  Other than a nearby lightning strike destroying my filter,
router and one NIC, it works pretty well.  It's very similar to your
diagram.

Bob...

On Wed, 2006-05-10 at 10:44 +0200, Juergen K. Zick wrote:
> Well,
> 
> 
> >Bellsouth gave me a box of filters that have two RJ-11 jacks.  One for
> >the DSL modem and one for a phone.  The instructions specified that
> >every phone be connected to a filter.  The DSL modem would then be
> >connected to the DSL jack along with one of the phones.  The modem
> >should not be connected directly to a phone line.
> >
> >The point is to isolate (filter) the DSL signaling from the voice
> >signaling as Juergen describes.  However in the US the wiring is not,
> >typically, "home-run", but daisy chained, one wall plate to the next
> >with no place to put a whole house filter.  Telcos do not like customers
> >in the demark at the cable entrance and customers can install their own
> >DSL equipment.  I did.  Bellsouth mailed the equipment to me with a CD
> >and a set of paper instructions.  It's just easier to tell the DIY'r to
> >filter everything.
> 
> Yes, I was aware of that "daisy chain" problem. Nowadays, the same problems 
> are appearing in German flats as well, as many outlets / jacks are mounted 
> to the same line. And I agree that the TELCO advice for filtering 
> everything is much simplier for the DIY people, _BUT_ it can lead to a 
> mismatch of your phone line and additional reflections especially in the RF 
> band where the DSL signals are being located.
> German phone jacks (TAE jacks) are different from RJ jacks and include 
> switches. That mean that you can install the splitter into the _FIRST_ TAE 
> jack  connect your DSL modem to the splitter and the filtered POTS output 
> is automatically being sent into the the rest of the daisy chain ...
> The proposed filtering works _ONLY_ when your line to the DSLAM is quite 
> short and you have not a high attenuation on it.
> 
> --Jürgen
> 
> 
> 
> 
> But slowly, we are getting completely off-topic on this list. I doubt that 
> changing to static IP will solve to decribed problem, because it is a line 
> mismatch problem on the physical layer of the connection. And these will 
> not go away unless you change the wiring !
> 
> Hadar, I would suggest to try my wiring first before you take other action 
> to buy something. Also, while testing the line with BellSouth, I would ask 
> for BERT-tests in the ATM-layer loop of your DSL.connection while your 
> father has no phone talk on the POTS side and then with a running phone 
> talk on on his phone.
> 
> 
> 
> 
> >Bob...
> >
> >
> >
> >
> >
> >On Tue, 2006-05-09 at 20:41 +0200, Juergen K. Zick wrote:
> > > Well,
> > >
> > > to avoid a misunderstanding see the following drawing:
> > >
> > >
> > >
> > > 
> > /-------DSL-MODEM-----HT-----PC
> > >                                             H|                      |
> > >                                    +----------+ 
> > Inet-PHONE
> > > from BellSouth (DSL over POTS) ---| SPLITTER |
> > >                                    +----------+
> > >                                             L|
> > > 
> > \------------------------------
> > >                                                          | 
> >     |
> > >                                                      answering 
> >    POTS
> > >                                                      machine 
> >    phone
> > >
> > >
> > >
> > > (maybe you have to reformat it into COURIER font)
> > >
> > > It's depending on the calling in your father`s flat but on the incoming
> > > line you should have only _ONE_ device, the SPLITTER !!!
> > >
> > > maybe your dad can try that ...
> > >
> > > All DSL connections in Germany are build up like that and I have not seen
> > > any that did _not_ work with this cabling ...
> > >
> > >
> > > --Jürgen
> > >
> > >
> > >
> > >
> > > >Juergen K. Zick wrote:
> > > >>HI,
> > > >>well, that was what I expected in my posting yesterday. For me, your
> > > >>wiring looks strange. Here in Germany, we have "spiltters" connected to
> > > >>the incoming line which have two outputs: A high pass filter output for
> > > >>the DSL signal and a low pass output with DC  pass-through for the POTS
> > > >>signal. the DSL output is being connected to the DSL-modem and the POTS
> > > >>output will feed your internal POTS wiring.
> > > >
> > > >The only jack that has both a phone and the DSL connector indeed has a
> > > >splitter on it, provided by Bellsouth.
> > > >
> > > >>Therefore, there is _NO_ filter needed on each POTS outlet, because 
> > there
> > > >>is nothing to be filtered out on your internal line anymore.
> > > >
> > > >You may be correct. I am definitely _not_ familiar enough with DSL.
> > > >However, 5 years ago, I had a DSL line in my apartment, and I was
> > > >specifically told by the installation tech that I needed a filter on 
> > _any_
> > > >jack that had a real phone connected to it. That may not have been
> > > >necessary, or perhaps isn't necessary any longer, or perhaps varies by
> > > >provider, but that's what I was told at the time, and that's what I did
> > > >(with no problems).
> > > >
> > > >The filters on the phone jacks that didn't have the modem connected were
> > > >not splitters, just single filters.
> > > >
> > > >>Seen from my German wiring knowlegde, your cabling is wrong and causes
> > > >>the interruptions on the DSL service.
> > > >
> > > >That's definitely possible, just not my personal (single point!) 
> > experience.
> > > >
> > > >>Don`t you have something like a "spiltter" available ? It should be the
> > > >>_ONLY_ filter on your incoming line and then the DSL-modem and the POTS
> > > >>phone should be connected to it ...
> > > >
> > > >OK, it would be easy for him to remove the other filters temporarily and
> > > >test again.
> > > >
> > > >Thanks!
> > > >
> > > >>--Jürgen
> > > >
> > > >>>Replying to my own post (and my most recent follow-up). I have now
> > > >>>confirmed 100% that the DSL modem gets a _new_ IP address every time 
> > his
> > > >>>"real" phone gets answered, or hung up! This (of course) disrupts the
> > > >>>audio coming from to him, since the sending machine (Asterisk in my
> > > >>>case), no longer has the correct IP address to send to him.
> > > >>>
> > > >>>I lowered his registration from the default 1 hour to 1 minute, so 
> > after
> > > >>>we're disconnected, I can see that he's re-registering with a new IP
> > > >>>address, each and every time :-(.
> > > >>>
> > > >>>I told him to call Bellsouth and ask about a Static IP address, but I
> > > >>>don't know if they offer it, or how much they charge.
> > > >>>
> > > >>>While this one isn't "solved", it's at least "explained".
> > > >>>
> > > >>>Thanks to everyone who responded!