Oki 1.2 - Manual (Page 45)

37 Setup
Add: Click on this button to add a VoIP telephone number, IP address or
port number in the address table.
Change: Click on this button to change the contents of the address table.
Click on the line where a change in the VoIP telephone number, IP
address, or port number is to be made, then make the changes in the
selected line.
Clear: Select the line to be cleared, and then click on this button to clear
the entire selected line.
All Clear: Click on this button to clear all information in the address
table.
The VoIP-TA port number is 1720.
When specifying another gateway, enter a port number specified for the
call (usually 1720).
*