Bitting of line

[jgeneie]

I have start up 2x VoIP boxes and they are working fine. but the problem is that when any party hangs up, the line will still be hook-on for around 3 mins. seems like the box doesnt recognise the "hanging up" tone. im using voltel mosa 4500 series.

my senario is

pstn --> pbx --> Voip gateway --> router --> internet

the same setup for the other side.

please advice

genie