Draytek Vigor2920 Series User Manual page 333

Dial Out Account
Loop through
Backup Phone Number
Secure Phone
Choose one of the SIP accounts for this profile to dial out. It is
useful for both sides (caller and callee) that registered to
different SIP Registrar servers. If caller and callee do not use
the same SIP server, sometimes, the VoIP phone call
connection may not succeed. By using the specified dial out
account, the successful connection can be assured.
Choose PSTN to enable loop through function.
When the VoIP phone is obstructs or the Internet breaks down
for some reasons, the backup phone will be dialed out to
replace the VoIP phone number. At this time, the phone call
will be changed from VoIP phone into PSTN call according to
the loop through direction chosen. Note that, during the phone
switch, the blare of phone will appear for a short time. And
when the VoIP phone is switched into the PSTN phone, the
telecom co. might charge you for the connection fee. Please
type in backup phone number (PSTN number/ISDN number)
for this VoIP phone setting.
ZRTP+SRTP: A call made to the number specified in the
phonebook will be "compulsorily" encrypted. If the encryption
is not successful (e.g. peer side does not support ZRTP/SRTP),
a warning voice should be played.
Note: If the incoming or outgoing calls do not match any
entry on the phonebook, the router will try to make the call
"being protected". But, if the call ends
up "unprotected"(e.g. peer side does not support
ZRTP+SRTP), the router will not play out a warning
message.
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Vigor2920 Series User's Guide