[asterisk-users] Answer Supervision problem

[Timur S. Sattarov]

 Hi !

I've Linux Debian/testing, asterisk-1.2.13, zaptel 1.2.10 and Digium, 
Inc. Wildcard TDM2400P with 24 FXO ports.
Our equipment is located in US. Lines and phone numbers from AT&T.
How can I detect answers on these lines ?
We've discovered that during answer voltage falls and after hangup - rises.
During remote hangup there is kernel message from zaptel driver  - NO 
BATTERY on 2/24 and then BATTERY on 2/24 (-)! and 
hanguponponlarityswitch option in zapata.conf works fine.
There is no such message during answer. But we can see voltage change. 
Is there any way to detect answer like we have on hangup ?
Or if there any possibility to detect answer through voltage changes 
with zaptel ?
Please help me.

Thanks in advance.

With best regards
Timur.