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Advanced Options for Voice Services
VoIP-to-PSTN and PSTN-to-VoIP Calling
Cisco SPA232D Administration Guide 220
C
Configuring VoIP Failover to PSTN
When power is disconnected from the ATA, the FXS port is connected to the LINE
port. In this case, the telephone attached to the FXS port is electrically connected
to the PSTN service via the LINE port. When power is applied to the ATA device,
the FXS port is disconnected from the LINE port. However, if the PSTN line is in use
when the power is applied to the ATA device, the relay is not flipped until the
PSTN line is released. This feature ensures that the ATA device does not interrupt
any call in progress on the PSTN line.
When Line 1 VoIP service is down (because of registration failure or loss of
network link), the ATA device can be configured to automatically route all outbound
calls to the internal gateway using the parameter listed below.
You can configure this setting on the Voice > Line 1 page.
Sharing One VoIP Account Between the PHONE and LINE
Ports
Both the PHONE port (Line 1) and LINE port (PSTN) can receive incoming calls for a
single VoIP account. Consider the following points:
• If the service provider allows multiple registration contacts and
simultaneous ringing, both lines can register periodically with the service
provider. In this case, both lines receive inbound calls to this VoIP account.
The PSTN Line should be configured with a sufficiently long answer delay
before the call is automatically answered to allow for the function of the
PSTN gateway.
• If the service provider does not allow more than one register contact, the
PSTN Line should not register. In this case, only Line 1 rings on the inbound
call to this VoIP account because it is the only line registered with the
service provider.
• Line 1 can have the call forwarded to the PSTN Line after a few seconds
using the Call-Forward-On-No-Answer feature with gw0 as the forward
destination. Similarly, Line 1 can apply Call-Forward-All, Call-Forward-On-
Busy, and Call-Forward-Selective feature, and direct the caller to the PSTN-
Gateway.
• Only PIN authentication is allowed when a VoIP caller is forwarded to the
PSTN-gateway from Line 1. If HTTP Authentication is used, the caller is not
authenticated.