Cisco Systems PAP2T, SPA2102, SPA3102, WRP400, SPA8000 manual Two-Stage Dialing

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

NOTE If Authentication is disabled, a default dial plan is used for all unknown VoIP users.

Two-Stage Dialing

In two-stage dialing, the ATA device takes the FXO port off-hook but does not automatically dial any digits after accepting the call. To invoke two-stage dialing, the VoIP caller should INVITE the PSTN Line without the user-id in the Request-URI or with a user-id that matches exactly the <User ID n> of the PSTN Line. A different user-id in the Request-URI is treated as a request for one-stage dialing if one- stage dialing is enabled, or dropped by the ATA device (as if no user-id is given) if one-stage dialing is disabled.

NOTE If Authentication is disabled, a default dial plan is assigned to all VoIP callers.

HTTP Digest Authentication can be also used for two-stage dialing, as in one- stage dialing. If using HTTP Digest Authentication or Authentication is disabled, the VoIP caller should hear the PSTN dial tone right after the call is answered (by a SIP 200 response).

If PIN Authentication is enabled, the VoIP caller is prompted to enter a PIN number after the ATA device answers the call. The PIN number must end with a # key. The inter-PIN-digit timeout is 10 seconds (not configurable). Up to eight VoIP caller PIN numbers can be configured on the ATA device. A dial plan can be selected for each PIN number. If the caller enters a wrong PIN or the ATA device times out waiting for more PIN digits, the ATA device tears down the call immediately with a BYE request.

NOTE When the source address of the INVITE is 127.0.0.1, authentication is automatically disabled because this is a call by the local user. This applies to both one-stage and two-stage dialing.

ATA Administration Guide 97