Draytek Vigor2500V Series Quick Start Manual page 21

For each Dial Plan, you will see the settings below:
The detail explanation of the index window:
Enable
Phone Number
SIP Address
Loop Through
Backup Phone
Number
Tick this to enable this entry.
The "Speed-dial" number of this index. This can be any number
you choose, using digits 0-9 and*
Enter your friend's SIP URL
This function provides comprehensive ways to call your friend.
PSTN/ISDN: When the router detect your Internet connection is
available, the router will dial SIP URL so your call will be directed
via Internet. If the Internet connection is down, Loop Through
function enable the router automatically dial Backup Phone
Number so your call will be directed via PSTN/ISDN network. This
ensures your call will always be dialed.
This is important because you don't want your call get trapped in
the VoIP mechanism. Please be sure to fill in the Backup Phone
Number.
None: The router will always dial SIP URL no matter what the
status of Internet connection is. It might cause your call failed due
to the Internet connection might not be available.
Although the Loop Through function provides convenient
live lines for your call, you might prefer None for directing
all calls via Internet. Please be reminded that you can still
make the call via PSTN by manually dialing "#0" first or
ISDN by manually dialing "#*".
This will also work if you may wish to know in which way
every call dial out so that you can count how much they
save before receiving the phone bill.
The telephone number to dial if you select PSTN / ISDN in Loop
Through
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