Grandstream Networks UCM6510 User Manual page 63

Insecure
Enable Keep-alive
Keep-alive Frequency
Other Settings
SRTP
Fax Detection
Strategy
Firmware Version 1.0.0.5
"RFC2833". If "Info" is selected, SIP INFO message will be used. If
"Inband" is selected, 64-kbit codec PCMU and PCMA are required.
When "Auto" is selected, RFC2833 will be used if offered, otherwise
"Inband" will be used.

Port: Allow peers matching by IP address without matching port
number.

Very: Allow peers matching by IP address without matching port
number. Also, authentication of incoming INVITE messages is not
required.

No: Normal IP-based peers matching and authentication of
incoming INVITE.
The default setting is "Port".
If enabled, empty SDP packet will be sent to the SIP server periodically
to keep the NAT port open. The default setting is "Yes".
Configure the number of seconds for the host to be up for Keep-alive.
The default setting is 60 seconds.
Enable SRTP for the call. The default setting is "No".
Enable to detect Fax signal from the user/trunk during the call and send
the received Fax to the Email address configured for this extension. If no
Email address can be found for the user, send the received Fax to the
default Email address
GUI->PBX->Internal Options->Fax/T.38.
Note:
If enabled, Fax Pass-through cannot be used.
This option controls how the extension can be used on devices within
different types of network.

Allow All
Device in any network can register this extension.

Local Subnet Only
Only the user in specific subnet can register this extension. Up to
three subnet addresses can be specified.

A Specific IP Address.
Only the device on the specific IP address can register this
extension.
The default setting is "Allow All".
UCM6510 IP PBX User Manual
in Fax setting page under web
Page 62 of 192