Here is some info I put together a while back when I was setting it up.
PBX Programming
Station Programming
Add a new station (this station should be your Ascom wireless extension)
Port = X
Security Code = 6 digits
Keys 4-5 should be programmed as brdg-appr for your personal extension number
On page two of the program form you will need to change bridge call alerting to Yes
Off PBX Telephone station-mapping programming
Change off-pbx-telephone station-mapping XXXXX (your ascom extension number)
Type in your extension number as the station extension
Set the Application to OPS
Set the Phone Number to the same as the station extension
Set the Trunk Selection to 13
Set the Config Set to 1
Portable Device Manager Programming (Browser)
The Ascom phone needs to be release 1.4.21
You must then use a template from a working SIP phone
Once the template has run you must change the below parameter settings
Device/User/User display text should be set to the correct name
Device/User/endpoint number should be set to the Ascom extension
Device/User/endpoint ID should be set to the Ascom extension
Device/General/Voice Mail Number should be set to XXXXX (users VM number)
Device/Unite/IMS phone number should be set to the Ascom extension
Protocol/SIP/Proxy Password should be set the same as the PBX station security code
Save
SIP Server Programming
Login = admin
Password = XXXXX
Select add user
Primary Handle = Ascom extension
User ID = Ascom extension
Password = the same as the PBX station security code
Enter the 1st and last name
Check the box to Add media server extension
Select Add
Select Continue
Add the media server extension (Ascom extension number)
Select continue
Under the Host selection on the side menu
Select update all