[Asterisk-Users] Major problems with TDM400 and specific telephones: suggestions?

[Andrew Kohlsmith]

On March 22, 2005 03:08 pm, tmassey at obscorp.com wrote:
> The phone in question is what I would consider to be a good-quality GE
> two-line cordless telephone.  Digium's guess is that it is "putting power
> on the telephone line and the card doesn't like that."  They have given me
> zero solution other than to use a different telephone.

I have a Panasonic 900MHz digital cordless phone that also causes the TDM card 
to have fits.  I've sent it to Digium to try and figure out what's going on, 
as every single other phone and fax (probably two dozen brands between the 
two) I have ever hooked up has worked just fine.  This is not a normal thing 
and it may just be that the actual POTS system is able to handle their 
particular brand of yuck.

I certainly don't blame Digium for this, but they have been more than willing 
to help me correct it, especially since I am willing to get the phone to them 
to test with since they seem to be unable to recreate it in their lab.  My 
5.whateverGHz Panasonic digital cordless phone works great, and my 900MHz 
non-digital (cheapass) cordless phone works great.

> As an aside, why is it that just about *any* other device with an analog
> interface you can buy today more robust than the TDM cards?  I've used
> countless different ISDN NT-1's without problems, from $100 cheapo models
> to $1000 high-end devices and tons in between and none have had problems
> like this.  Now there's a ton of SIP gateway devices.  They don't seem to
> have these issues.  Why do the TDM cards?  And most importantly, can an
> end user do anything about this?

As I said, I've hooked up countless devices to the TDM cards and this 
particuar phone is the ONLY one I've had trouble with.  It is perhaps a 
corner case in the TDM design, but as I said Mark has personally been more 
than willing to help fix this.

As an electronics designer myself, I know how unbelievably frustrating it is 
to have a customer with an issue and not be able to recreate it myself such 
that a fix can be found.

-A.