You're right, the gxw is not alerting fs at all, i did some testing and there is absolutely nothing on the debug console (after pressing F8) between the moment i put the user on hold and the moment i pick up the call again.

"You might need to use tone_detect. See the example at the bottom (this is how I use it to detect a hang up as my telco doesn't vary the voltage levels on hangup)":
It recognizes when the hang up is done before picking up, but after picking up it won't recognize the hang up.
I tried configuring this on my dialplan configuration to-pstn then i dialed to an extension that would pick up and then hang up on me, but it didn't do the magic, I also tried adding it to the anti-action options on the default dialplan for the extensions 100X and testing again but it didn't work either,
I tried calling to my telco to get info on what kind of hangup signal did they send but i got stuck into a cycle of a person bouncing me to the "assigned area" over and over again.
Maybe the frequences i tried were not the right ones... maybe the gateway can be configured without having information about my telco... i don't know, i'll try asking for support on the Grandstream site.

2009/1/7 Michael Collins <msc@freeswitch.org>

What version of FreeSWITCH are you on? Also, can you get a debug trace from when the far end hangs up? We definitely need to know if the gxw is alerting FS to the fact that the far end actually hung up, which is in doubt right now.