Cisco Systems SPA3102, SPA2102, WRP400 Terminating Gateway Calls, Parameter Web Description Values

Configuring the PSTN (FXO) Gateway on the SPA3102	6
How PSTN-To-VoIP Calls Work

Terminating Gateway Calls

There are two call legs in a PSTN gateway call: the PSTN call leg and the VoIP call leg. A gateway call is terminated when either call leg is ended. When the call terminates, the FXO port goes on-hook so the PSTN line can be used again. The ATA device detects that the PSTN call leg is ended when one of the following conditions occurs during a call:

•The PSTN Line voltage drops to a very low value (this occurs if the line is disconnected from the PSTN service or if the PSTN switch provides a CPC signal).

•A polarity reversal or disconnect tone is detected at the FXO port.

•There is no voice activity for a configurable period of time in either direction at the FXO port.

When any of the above conditions occur, the ATA device takes the FXO port on hook and sends a BYE request to end the VoIP call leg. On the other hand, when the ATA device receives a SIP BYE from the VoIP during a call, it takes the FXO port on hook to end the PSTN call leg.

In addition, the ATA device can also send a refresh signal periodically to the VoIP call leg to determine whether the call leg is still up. If a refresh operation fails, the ATA device ends both call legs.

The following table lists parameters for terminating gateway calls.

Parameter	Web	Description	Values
	Page
Detect CPC	PSTN	If yes, the ATA device detects CPC as a	Yes or No
	Line	disconnect signal.	The default
			is Yes.
Detect Long	PSTN	If yes, the ATA device detects prolonged	Yes or No
Silence	Line	silence period as a disconnect signal.
Long Silence	PSTN	The minimum duration of continuous	10-255
Duration:	Line	silence before the ATA device	The default
		disconnects the call, if the Detect (PSTN)
			is 30(s).
		Long Silence parameter is enabled.

ATA Administration Guide 99