How Voip-To-Pstn Calls Work; One-Stage Dialing (Spa3102 And Spa8800) - Cisco SPA2102 Administration Manual

Configuring the PSTN (FXO) Gateway on the SPA3102

How VoIP-To-PSTN Calls Work

How VoIP-To-PSTN Calls Work
Cisco Small Business ATA Administration Guide
- FXO Port: The SPA3102 has 1 FXO port that you can connect to the
PSTN. Configure the FXO settings by using the SPA3102 PSTN Line
page.
• The SPA8800 is designed to work with your PBX as a PSTN gateway and a
VoIP gateway. Call control is provided by a standard PBX, an Asterisk-
based IP PBX, the SPA9000 Voice System, or an Internet-based call control
system.
- FXS Port: The SPA8800 has 4 FXS ports that you can connect to
standard analog telephones or fax machines. Configure the FXS settings
by using the SPA8800 Phone 1-4 pages.
- FXO Port: The SPA8800 has 4 FXO port sthat you can connect to the
PSTN. Configure the FXO settings by using the SPA8800 Line 1-4 pages.
To obtain PSTN services through the SPA3102 or the SPA8800, the VoIP caller
establishes a connection with the PSTN Line by way of a standard SIP INVITE
request addressed to the PSTN Line.

One-Stage Dialing (SPA3102 and SPA8800)

One-stage dialing allows a call to be started over VoIP and then immediately get a
dial tone on the PSTN. When you take a phone off hook and dial a number, the call
is automatically routed to the VoIP or the PSTN, based on the dial plan.
On the SPA3102, you can enable HTTP Digest Authentication. In this case, the
SPA3102 challenges the INVITE with a 401 response if it does not have a valid
Authorization header. The Authorization header should include a <
parameter, where n refers to one of eight VoIP user accounts that can be
configured on the ATA device. The credentials are computed based on the
corresponding password using Message Digest 5 (MD5). The <
parameter must match one of the VoIP accounts stored on the ATA device. You can
configure these settings on the Voice tab > PSTN Line page. For more information,
see “VoIP Users and Passwords (HTTP Authentication) section,” on page
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