[Asterisk-Users] TDM400P Revision question.

[Rich Adamson]

> >> > > I was following a discussion on this list about the 
> >>TDM400P 
> >> > revisions. 
> >> > >It is my understanding that the current revision that 
> >>one 
> >> > should have 
> >> > >is the Rev. H and not the E/F. I have not yet been 
> >>able to 
> >> > verify the 
> >> > >rev stamped on the board, but zaptel is reporting 
> >>that I 
> >> > have the Rev. 
> >> > >E/F. I just bought this card in January direct from 
> >>Digium and was 
> >> > >wondering if I got the wrong Rev.
> >> > >somehow?? I have been having some intermittent 
> >>problems but only 
> >> > >thought it was my setup.
> >> > > 
> >> 
> >> 
> >> 
> >> I did some more testing today. I called Digium on 4/12 
> >>and they
> >> suggested some things to try, like different 
> >>motherboard, switching pci
> >> slots, etc.. I did everything they asked, except for the 
> >>mother switch
> >> as I do not have a different one to put in the system at 
> >>this time.
> >> 
> >> So, after all that, my ringing issue still persists. Too 
> >>some
> >> measurements from bot the card and my POTS line in both 
> >>the on-hook
> >> state and ringing state. I uses a digital multi-meter to 
> >>make the
> >> measurements on both. Here are the results....
> >> 
> >> TDM400P
> >> 
> >> Before slot change:
> >> 
> >> On hook idle:
> >> 
> >> 43.8 Volts DC
> >> 0    Volts AC
> >> 
> >> Ringing:
> >> 
> >> 0    Volts DC
> >> 56.4 Volts AC
> >> 
> >> After slot change:
> >> 
> >> On hook idle:
> >> 
> >> 48.7 Volts DC
> >> 0    Volts AC
> >> 
> >> Ringing:
> >> 
> >> 0    Volts DC
> >> 65.5 Volts AC
> > 
> > We can only assume the above represents a fxs module on 
> >the
> > card. Correct?
> > 
> > I would find it hard to believe that changing slots 
> >would cause
> > the on hook DC voltage to change from 43v to 48v. That 
> >smells like
> > a funcky voltmeter. Slots should have nothing to do with 
> >DC
> > voltage unless the module is simply bad. The AC 
> >(ringing) voltage
> > is reasonable, but again it should not have changed 
> >simply
> > because of a slot change; again, questionable voltmeter.
> > 
> >> On my POTS line:
> >> 
> >> On hook idle:
> >> 
> >> 43.8 Volts DC
> >> .013 Volts AC
> >> 
> >> Ringing:
> >> 
> >> 50.5 Volts DC
> >> 93.9 Volts AC
> > 
> > The on hook DC voltage from all US telco's will 
> >factually be
> > in the 48v to 52v range. If their central office 
> >equipment produced
> > 43 volts, they would have alarms going off all over the 
> >place.
> > Their alarms would trigger somewhere in the 46 to 48 
> >volt range.
> > So, that measurement implies the voltmeter is not 
> >accurate.
> > The AC (ringing) voltage is well within acceptable telco 
> >limits
> > and can range from about 70v to upwards of 105v.
> > 
> >> Could it bee that from the phone company they retain the 
> >>DC offset
> >> voltage while applying a ring frequency and as it 
> >>appears on the TDM it
> >> shuts off the DC offset when ringing starts. Could this 
> >>be the issue
> >> with those of us in the U.S. having ringing issues with 
> >>the TDM's??
> > 
> > Doubtful that is an issue. The reason for saying that is 
> >the chipset
> > used on the fxo & fxs modules was manufactured by 
> >Silicon Labs, and
> > those same chipsets are used in other telephony 
> >equipment worldwide.
> > Silicon Labs is known for good to excellent products. If 
> >their chipsets
> > didn't function correctly, there would have been a large 
> >uprising a
> > couple of years ago when those chips were first 
> >produced. That
> > hasn't happened, and they don't have a lengthy chip 
> >revision history.
> > 
> > Asterisk code does not have any control over 
> >adding/removing the DC
> > component during ringing, so that's not an issue either. 
> >Doubtful
> > that adding/removal the DC component would have any 
> >impact on 
> > normal telephone sets, however there certainly could be 
> >funcky sets
> > that don't like that DC removal.
> > 
> > Given the number of postings relative to the TDM card 
> >lately, I don't
> > remember exactly what your ringing issue was. Could you 
> >remind us
> > without deleting the significant parts of the above?
> > 
> > 
> 
> Even though it is long, I will leave everything intact.
> 
> I have had a few issues with dropped calls when using the 
> FXS to FXO connection. Not sure what the issue is with 
> that. THe main issue I have is with the ringing on the FXS 
> card. I have three differnt brands of phones and all three 
> do the same thing. I might get two or three calls in where 
> everything works fine. But then the next one will cause 
> intermittent ringing one all phones and no data for caller 
> id.
> 
> I have tried every combination of the phones I have that 
> is possible. From only one of each type hooked directly to 
> the FXS card to hooking the card to my internal house 
> wiring and using various combos of the phones connected.
> 
> It almost acts like the phones are requiring just a hair 
> more ring voltage to work properly. That is why I was 
> testing the voltage levels. I will try and grab a 
> different meter to test with.

There is a compile-time option to increase the ring voltage.
I don't recall the specifics, but its likely in wctdm.c or
an associated header file. (As you probably can tell, I don't
use the fxs modules on my TDM card.)

> The system is a PIII 933MHZ, VIA chipset and has a 500 
> watt power supply in it. So I don not think it is a power 
> issue from the computer itself.

That shouldn't be a problem at all.
 
> The reason I asked about the DC offset during ringing, is 
> that on the telco side, I noticed that the offset remained 
> even when ringing voltage was applied. On the TDM, it does 
> not. In the manual for the chipset that someone sent me, 
> there is the option to apply a DC offset voltage during 
> ringing. Additionally, the telco side gives the 93 Volts 
> AC when ringing where the TDM is only supplying the 65 AC 
> as according to my meter. These tests were conducted 
> several times to get average readings.

I think you can safely assume that Mark (and/or digium) tested
the fxs modules with at least a couple of phones, so its unlikely
there is a software issue such as the offset parameter lurking.
 
> As far as the issue with DC voltage on the POTS line only 
> being  43.8 DC, my guess was that is just an issue with 
> voltage drop on the line because of distance between me 
> and the CO.

No possible way. If everything is truly on hook, there isn't
any current draw and therefore no way for a voltage drop to
occur. Basic ohm's law.
 
> If I need to answer anything else, please let me know.
> 
> 
> P.S. - I do realize that that the chipset is a good 
> shipset. I am just wondering if everything is setup 
> correctly in the zaptel driver for the proper programming 
> of the registers in the chipset to make it function within 
> specs.

I don't know about the fxs module, but I know for a fact that
the fxo module has more capability then what has been implemented
in the current driver.