Asterisk can't detect Hangup signalling!

Hi friends,
I have a card TDM400p (1 module fxo and 1 module fxs), and asterisk ver 1.4.20 and zaptel ver 1.4.11.
I have a problem, the call from Asterisk to analog phone of PSTN, when analog phone of PSTN party Hangup, but Asterisk do not detect Hangup signalling.

I config file zapata.conf following:

busydetect=yes
busycount=4
busypattern=500,500
callprogress=yes
progzone=br

File zaptel.conf:
loadzone=us
defaultzone=us
fxoks=1
fxsks=4

I from vietnamese, my country not standard tonelist. I must to choose progzone=br then asterisk was detect Ringing, Answer, and Hangup signalling (When i call to mobile of PSTN) but when call ro analog of PSTN then not detect signalling Hangup.

If you know about these problem, please help me.
Than’k and regard!