TDM800P CDR always shows ASWERED even if it was NOT answered

Hello are some days I am trying to solve this problem.
My configuration is:
TDM800P card with 1 FXO and 4 FXS ports
ZAPTEL 1.4.10
the problem is:
when I call from a sip client to another sip client ( extensions ) in the CDR database is correctly shown when the call was answered or not.
When I call from a SIP client to the outside PSTN via the line connected to the FXO port, all calls are in the ANSWERED state, below a piece of log:

1. 2008-04-30 15:02:47 SIP/105-b6… 105 “alessandroportatile” <105> 0335xxxx ANSWERED 01:11
the above call was NOT answered by my cell phone

I tried also tho change the parameter answeronpolarityswitch=yes in ZAPATA.CONF but the result is exactly the opposite, all calls are UNANSWERED and also a line containing an “s” in the DST column is added with the same time stamp instead of the called number.

This is my ZAPTEL.CONF

Autogenerated by /usr/sbin/zapconf on Thu Apr 24 14:39:09 2008 – do not hand edit

Zaptel Configuration File

This file is parsed by the Zaptel Configurator, ztcfg

Span 1: WCTDM/0 “Wildcard TDM800P Board 1” (MASTER)


channel 6, WCTDM/0/5, no module.

channel 7, WCTDM/0/6, no module.

channel 8, WCTDM/0/7, no module.

Global data

loadzone = us
defaultzone = us

Do I have to change loadzone and defaultzone to IT since I am in Italy?

Please help me to solve this problem because is essential for me to know WHEN a call is answered for correctly billing calls to my customers. I deeply searched into the forum and outside but the only tip I found is the ANSWERONPOLARITYSWITCH as described above.
Many thanks in advance for the help
Best regards

try to use
callprogress=yes in zapata.conf

If you search this forum and many others. you will see that accurate billing is not possible with Alog trunks. If you want to bill use either ISDN, SIP or IAX as these all provide answer supervision.


Hello many thanks for the suggestions but I already tried the CALLPROGRESS and BUSYDETECT parameter without success; I made a lot of checks and definitely there is no way to have on CDR record the correct state of a call, ANSWERED or NOT.
I think that this problem is on due to the FXO hardware interface that doesn’t correctly detect when a call was answered or not.
Please someone has other ideas to solve this problem?
Many thanks


As I said you cant use Alog trunks as they will in almost all cases report answered when the call starts.
This is the case for almost all PBXs. (or at least all the ones I have come across in the last 27 years)
As I said move to a trunk that supprts answer supervision.


Thanks Ian for your support.
At this point I will move to a GSM SIP gateway and some DID’s so all calls, I think, will be correctly documented.
Thanks again for your support.

Hi If you are going to use a SIP -> GSM gateway expect to get the same problem as many answer the call and then call the GSM leg. You will need to check with the supplier.


Ciao Alessandro,
sei riuscito a venirne a capo.

Se si ci fai sapere, grazie