The gateway is responsible to detect and notify the peer side of the call when the remote party is disconnected. This function is called disconnect supervision. This section explains the attributes that controls how the gateway detects PSTN call disconnect.

By default the carrier does not notify the FXO port when the remote party is disconnected. In such case the gateway could be configured to disconnect the call when one if the following conditions occurs:

However, it is possible to ask the carrier to provide feed-back when the remote end is disconnected. The following modes exist: