[Asterisk-Users] TDM400P Revision question.

[Robert Webb]

On Thu, 14 Apr 2005 08:14:37 -0600
  Rich Adamson  <radamson at routers.com> wrote:
> 
>> > > 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.

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.

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.

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.

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.