Listed below are detailed instructions for each of the parameters available on the Modify Existing Extension - SIP & Dialing Tab:

SIP Extension Provisioning Password

This is the password that permits the phone to register with the PBX.  For IP phones that you configure manually, you will need to copy this password and paste it into the account registration password field in the phone user interface.  If you are using Protel LTS auto-provisioning tools, this password is loaded into the phone automatically.  Please use letters and numbers only - no special characters.  We strongly recommend using a very robust, random text string to secure your system and prevent unauthorized registrations and theft of phone service.  It is also a good practice to store this password in a spreadsheet document that contains all of your users, extension numbers, MAC addresses, IP addresses and SIP passwords.  An example of an excellent password is TWP873skt788CJK.  15 characters, alternating letters and numbers, with a mix of upper and lower case letters.

Trunk Selection

By default, every extension will use the default trunk settings in the PBX to place outbound calls.  If you want to override the default, select the desired trunk from the drop down menu.

NAT & Keep-Alive

Network Address Translation.  If the end point (IP Phone) for this extension will be connecting on the same LAN or VLAN as the PBX, you do not need to activate this option (although it will still work if you do).  If the phone will be connecting from a remote location that is not on the same network as the PBX, this option must be turned on.  Turning on NAT tells the PBX that the phone is connecting from an external IP address through a NAT router.  This is very important for the proper addressing of RTP (Real Time Protocol) media.  The Keep-Alive option is on by default and should be left that way.

Incoming Call Limit

This limits the number of concurrent calls that the PBX will allow for this extension.  The default is 2, meaning that if the user is on a call, an incoming call will activate the second line appearance on the phone, but if both "lines" are in use, an incoming call will go straight to voicemail.  You may want to set this to a higher number depending on the user and the number of call appearances you can program into the phone.

Caller ID

Each trunk in the PBX is configured with a default caller ID.  All extensions are, by default, going to use that caller ID for outbound calls unless you override it here.  You can select any DID number that is provisioned in the PBX as caller ID.  Keep in mind that PBX-generated caller IDs only work on SIP trunks.  If your PBX is using a PRI or standard POTS lines for outbound calls, the caller ID is set by the phone company and this PBX setting will have no effect.  If you want to program advanced caller ID settings, such as for E911, see further instructions HERE

Extension Display Override

In some complex dialplans, a published extension number for a particular user is actually a group number in the PBX, and the person for whom the group extension number is published has a different peer extension number so that his phone can register to the PBX.  In that event, you want to override the extension display so that when that "boss" user makes an internal call, the group number displays on the receiving phone and not the actual peer registration number.

Area Code for 7-Digit Dial

The PBX trunk configurations have an optional setting for 7-digit dialing, which becomes the default for all users.  If you want to override this for a particular user, enter the 3-digit area code for the PBX to add to 7 digit numbers.  This is generally only used if you have a remote user in a different area code and you want them to be able to dial their local numbers without the area code.  This feature is becoming less used, since most area codes in the USA and Canada have already deployed, or will deploy soon, a 10-digit dialing requirement.

Number of Rings before Going to Voicemail or Forward

This determines how long this extension will ring before voicemail kicks in.  Or, if you are using a delayed PBX forward that you set from the extension user interface (not a feature code forward), how long it will ring before the forward kicks in.  This entry is made in "number of rings", but since phone manufacturers vary, you may need to adjust this setting to achieve your desired delay.  If this extension does not have voicemail activated, the PBX will terminate the call when the time limit is reached, so we advise setting this to a high number for an extension with no voicemail.  The maximum value here is 99.