I have 2 sites, one site is a 3640 to PSTN via FXO, the other site is a 5300 to a switch. I use Connetion PLAR to connect 2 sites via internet. The IOS in 3640 is IOS (tm) 3600 Software (C3640-JS-M), Version 12.2(31), RELEASE SOFTWARE (fc2), in 5300 is IOS (tm) 5300 Software (C5300-JS-M), Version 12.3(6), RELEASE SOFTWARE (fc3). My problem is sometimes when users finished a call, the call did not hang up in the switch, especially when there is no one answer at the switch side, this call will be busy for a long time in the switch. Is there any configuration in the 5300, like a FXO supervisory disconnect, to inform the switch when the call has been hung up. But I do not have this problem with this 5300 with other voice traffic, like the traffic from another 5300.