[Asterisk-Users] tdm400p static - out of ideas

[Ryan Courtnage]

On 8-Jul-04, at 9:37 AM, Jorge Mendoza wrote:

> We have not experience with Digium cards. However we had similar 
> problems when installing legacy pbx. The problem: local ground. One 
> easy way to test the local ground is with a voltmeter measure the 
> voltage between the CO tip wire (in open loop state) and local ground. 
> This must be less than 2 VDC and must be stable (not oscillations). 
> Correcting the local ground all problems were fixed.
> When you plug a regular phone, the phone is floating and have not 
> electrical contact with other devices, then there are not ground 
> currents.
> My guess is that there are some hardware design that are more 
> sensitive than others to ground currents.

This is very good advice - I will certainly check for this.

Digium has suggested that loading the driver like this will resolve the 
static noise problems I've been seeing:

	modprobe wcfxs lowpower=1

I'll report back in a few days with the results.

I'd like to know exactly how this will fix the prob (ie: the chain of 
events that occur to create the problem).


>
> Hope this helps.
>
> Jorge
>
> Ryan Courtnage wrote:
>> On July 8, 2004 03:22 am, Nicholas Bachmann wrote:
>>> Ryan Courtnage wrote:
>>>
>>>> Hello,
>>>>
>>>> Over the past several weeks, we have been having an intermittant 
>>>> problem
>>>> with our deployment of a TDM400P card (4 fxo).  We have tried many
>>>> things, and the problem still re-occurs.
>>>>
>>>> The Problem:
>>>>
>>>> Occasionally (every 48 hours), the TDM400p card will stop answering
>>>> incoming calls on ALL fxo ports.  Attempts to send outbound calls 
>>>> on any
>>>> Zap channel will result in hearing a loud 'static' noise on the 
>>>> line.
>>>
>>> Let's look at some possibilities of line problems:
>>> What time does it stop answering? Is it ever during ALIT times 
>>> (usually
>>> very early morning)?
>> It's totally random - morning/evening/afternoon.  Once it stops 
>> answering, that's it, a reboot or module-reload is needed.  If ALIT 
>> for some reason prevents the card from answering, it should be able 
>> to recover and begin answering after the ALIT is complete.
>>> Have you tried calling the telco to see if it could be their problem?
>> When the card goes into the non-functional state, I can plug a 
>> regular phone into any of the lines and make calls just fine.  After 
>> verifying working lines and plugging them back into the tdm400p card, 
>> I still can't dial out (the Zap channel will answer, but I will hear 
>> only static, and the call to the pstn is never placed).  As well, 
>> incoming calls will not be answered (* console will not even show the 
>> 'started simple switch on zap/x' message).
>>> How far away from the CO/mux are you?
>> Not too sure - it's in downtown Calgary - so probably not far.
>> There is the possibility that _something_ with the phone line is 
>> triggering the problem.  Maybe it's some noise, an unexpected signal, 
>> some crosstalk ...  things that will cause unexpected behavior ... 
>> but also things that shouldn't put the entire card into a 
>> non-functioning state.
>>> Have you tried a new/different card?  If you didn't want to fork out 
>>> the
>>> cash for a new one, you could try a X100P/knockoff* on one of the 
>>> lines
>>> to see if that fixes the problem... if so you can deduce a bad card.
>> I may have to push for a replacement tdm400p card from Digium.
>>> Nick
>>>
>>> *I usually don't recommend the knockoffs, but for a day of testing 
>>> $10
>>> sure beats $100... everybody else should support Digium! :-)
>> An acquaintance who is having the same problem has reluctantly 
>> replaced his card with an openline4.  I would like nothing more than 
>> to stick with Digium hardware - this thread and obtaining a 
>> replacement card is my last kick at the cat.
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