How Pstn-To-Voip Calls Work; Terminating Gateway Calls - Linksys RTP300 - Broadband Router With 2 Phone Ports Administration Manual

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 on-
hook 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 Web
Page
Detect CPC PSTN
Line
Detect Long Silence PSTN
Line
Linksys ATA Administration Guide
Configuring the PSTN (FXO) Gateway
Description
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.
How PSTN-To-VoIP Calls Work
Values
Yes or No
The default is
Yes.
Yes or No
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