[asterisk-users] Problem: Digium TDM400 with XOptionsFlex - Line Busy

[John Novack]

Thomas Klettke wrote:
> Perhaps someone with more experience can help me solve this puzzle:
>
> Asterisk 1.4.18 on a Dell PowerEdge SC440, CentOS 5, 2.6.18-53.1.14.el5,
> Digium TDM400 with 3FXO(1-3) and 1FXS(4)
>
> Phone service is provided by XO Communications via their XOptionsFlex
> service (5 analog lines, 3 of which are used by Asterisk).
> For simplicity I refer to them as xx43, xx44, and xx45 - based on their
> phone numbers. They are connected to the Digium as follows:
>
> xx43 = FXO 1
> xx44 = FXO 2
> xx45 = FXO 3
>
> Here is the problem: 
> When I connect the Asterisk box to the analog lines the first two lines
> (xx43 and xx44) will instantly switch to "busy". xx45 works fine -
> incoming and outgoing calls work as expected.
>
> I had XO check the lines - all three lines are programmed the same in
> their equipment. The work OK - until they are connected to the PBX -
> when xx43 and xx44 instantly switch to "busy". 
>
> I checked the lines with an analog phone: Each line wokred fine when I
> plug an analog phone into it.
>
> I suspected that my FXO ports 1 and 2 may be bad. Thus I connected FXO 3
> - which is working with xx45 - to line xx43 and then xx44: They went
> "busy" right away in either case. 
> I connected FXO 1 and then 2 to line xx45: Worked fine both times.
>
> I replaced the entire TDM400 with another card, and repeated the above
> tests - the results were the same as above. 
>
> >From those experiments I think I can rule out that the card is
> defective, as every FXO channel works with line xx45. None of them work
> with lines xx43 and xx44.
>
> I finally replaced the Digium card with a Sangoma A200 with 4 FXO ports
> (using 1-3 while leaving 4 unused). All 3 lines work as they should.
>
> Does anyone have an explanation for this strange behavior? 
> Any suggestions on how to fix it? I would like to get the Digium card to
> work with this setup as I need the 4th (FXS) port for an analog
> extension in the office.
>   
Assuming you have also checked the obvious possible defects regarding 
cords from the XO device to the Digium card, what happens if you reverse 
tip and ring?  When you say "busy" does that mean the line appears to be 
in use when attempting to receive a call? If both a POTS phone and the 
FXO are connected, does the line appear dead, is there noise or static, 
or by busy is it only Asterisk that thinks the port is "busy" The only 
thing that immediately comes to mind is line polarity.
Not certain even if the Digium FXO circuit is even sensitive to line 
polarity, but I have seen some permanent failures to the module when 
connected to a device that produces an inductive kick when used in pulse 
mode.  These were attempts to interface very old telephony devices that 
were in use before semiconductors were even in a engineer's wet dream.
Clearly the Sangoma is a better card in many ways, but your needs would 
require you expand the A200 to do what you want.
That ultimately may be the best solution.

John  Novack

John Novack



-- 
Dog is my co-pilot