Chapter 16 VoIP
P-2601HN(L)-F1 Series User’s Guide
191
Each field is described in the following table.
16.9 
Technical Reference
This section contains background material relevant to the 
VoIP
screens.
16.9.1 
VoIP 
VoIP is the sending of voice signals over Internet Protocol. This allows you to 
make phone calls and send faxes over the Internet at a fraction of the cost of 
using the traditional circuit-switched telephone network. You can also use servers 
to run telephone service applications like PBX services and voice mail. Internet 
Telephony Service Provider (ITSP) companies provide VoIP service. 
Circuit-switched telephone networks require 64 kilobits per second (Kbps) in each 
direction to handle a telephone call. VoIP can use advanced voice coding 
techniques with compression to reduce the required bandwidth. 
Table 55 
VoIP > FXO
LABEL
DESCRIPTION
Pre-Fix For FXO Outgoing Call
Pre-Fix Number
Enter 1 - 7 numbers you dial before you dial the phone number, if you 
want to make a regular phone call while one of your SIP accounts is 
registered. These numbers tell the ZyXEL Device that you want to make 
a regular phone call.
Voice Features
Active G.168
Select this if you want to eliminate the echo caused by the sound of 
your voice reverberating in the telephone receiver while you talk.
Active VAD
Select this if the ZyXEL Device should stop transmitting when you are 
not speaking. This reduces the bandwidth the ZyXEL Device uses.
SIP Fail Over
Force to SIP if 
PSTN un-
plugged
Select this check box to have the ZyXEL Device redirect outgoing calls 
to the registered SIP account if the ZyXEL Device is not connected to 
the PSTN network.
When you try to make a PSTN call, but the PSTN port on the ZyXEL 
Device is unplugged, the ZyXEL Device uses the phone port’s registered 
SIP account to make the call.
Apply
Click
Apply
to save your changes.
Cancel
Click 
Cancel
to restore your previously saved settings.
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