5.2.9 VoIP-to-PSTN Calls
This function is applicable on FXO port that functions as a bridge between VoIP and PSTN. The user
can remotely use PSTN line to initiate a call.
To make a VoIP-to-PSTN call:
1. Dial the FXO SIP account phone number to establish the VoIP session. The caller will hear the
ring back tone once. Then the caller hears either a special continuous tone or a dial tone. The
special continuous tone is played if the pin code is configured, or the dial tone otherwise.
2. Enter in the pin code that is configurable on the configuration page. The caller will hear the dial
tone and get connected to the PSTN line if the pin code is valid, otherwise the continuous tone
is played again to prompt caller to enter in the pin code again. The use may try up to 3 times to
enter in pin code, if none is valid, HT488 will hang up.
3. After the caller hears dial tone from PSTN line, the caller can start dialing number to make
calls.
Note:
• Users can choose whether apply password protection for VoIP-to-PSTN calls or not. A PIN
(Pin for PSTN calls) consists of up to 8 numeric digits can be configured through BASIC
SETTINGS of the web configuration page. By default, there is no password protection, i.e.
there is no authentication required for callers on the use of PSTN line through HT488.
• When a PIN is configured for VOIP-to-PSTN call flow, the VoIP device that calls into the
HT488 FXO account needs to configure RFC2833 or SIP Info for DTMF digit transmission.
• Upon hearing the special continuous tone for PIN code input, if the caller don’t enter any digit,
HT488 will time out and hang up the call in 10 seconds. During any stage of DTMF digits
input, a 4 seconds timeout is applied to serve as an end of PIN or destination number input.
Users may also use the “#” key to indicate the end of an input.
• On the web configuration page, if the “Forward to PSTN” is configured, the second stage
dialing is eliminated, i.e., after dialing into the FXO SIP account number, the PSTN number
will be called automatically.