ShoreTel IP8000 Application Note page 8

The next item to change is under "Trunk Digit Manipulation" (Figure 12).
Typically when sending digits to the IP8000 phone it is not necessary to check the boxes for "Remove leading 1 from
1+10D", "Remove leading 1 for Local Area Codes" and "Dial 7 digits for Local Area Code' because only the extension digits
will be sent as this is an Off System Extension (OSE). No configuration is needed for the "Local Prefixes" parameter, or the
"Prepend Dial Out Prefix".
Next configure an Off System Extension for each IP8000
phone you will deploy.
Selecting the "Edit" button for the Off System Extensions
will bring up the "Off System Extension Ranges" dialog box
(Figure 13).
Figure 13 – Off System Extension Ranges
Selecting the "New" button will bring up the "New Range"
dialog box (Figure 14).
Figure 12 – Trunk Digit Manipulation
Input a new range of off system extensions for the IP8000
phone and click "OK". For this example the extension range
3000-3019 has been configured, although you only really
need one Off System Extension (OSE) defined, where First
and Last are the same number. This completes the settings
needed to set up the SIP Trunk Groups on the ShoreTel system.
Note: It is important to note that only one dynamic trunk
group can be set up per ShoreGear switch. If another
dynamic trunk group is desired another ShoreGear switch
will be needed.
Figure 14 – Edit Range for Off System Extensions
IP8000 Conference Phone Application Note—Page 8