Linksys RTP300 User Guide - Page 77

Configuring the PSTN (FXO) Gateway How PSTN-To-VoIP Calls Work How PSTN-To-VoIP Calls Work PSTN-To-VoIP calls can be made with two-stage dialing only. The only authentication method available is the PIN method. The Linksys ATA device takes the FXO port off hook after a configurable number of rings. If PIN Authentication is enabled, it prompts the caller to enter the PIN number followed by a # key. The Inter-PIN-digit timeout is set at 10 seconds. Up to eight PSTN PIN numbers can be configured in the Linksys ATA device. If the given PIN does not match any of the PSTN PIN values, the Linksys ATA device plays the reorder tone to the FXO port for up to 10 seconds, and then takes the FXO port on-hook. If the given PIN matches one of PSTN PIN values, the Linksys ATA device plays dial tone to the FXO port and is ready to accept digits for the target VoIP number from the PSTN caller. The collected digits are processed by the dial plan associated with the PIN number. NOTE: If Authentication is disabled, a default dial plan is used for all PSTN callers. 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 onhook so the PSTN line can be used again. The Linksys 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 Linksys 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 Linksys 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 Linksys 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 Linksys ATA device ends both call legs. The following table lists parameters for terminating gateway calls. Parameter Detect CPC Detect Long Silence Web Page PSTN Line PSTN Line Description Values If yes, the Linksys ATA device detects CPC as a disconnect signal. If yes, the Linksys ATA device detects prolonged silence period as a disconnect signal. Yes or No The default is Yes. Yes or No Linksys ATA Administration Guide 77