In order to realize this behavior you need to:

  1. Set the PA1 with a registered extension
    [Setup -> Identity -> Log In Information]


  2. Configure a speed dial with callee's phone number
    [Setup -> Speed Dial]


    More information on Speed Dial
    [See example 1 at the bottom of this article]  
    NOTE: 
    You can avoid the use of the speed dial if you match directly the input digit with the Dial Plan (see next point)

  3. Configure a dial Plan that match the speed dial digit and place call
    [Setup -> Identity -> SIP -> Dial-Plan String]


    How to use a Regular Expression: Dial-Plan
    [See example 2 at the bottom of this article]  


  4. Short circuit the Pa1 keyboard pin to simulate the button according to the following list:

     Key

     PIN

     PIN

    0

    2

    3

    1

    6

    2

    3

    4

    5

    6

    1

    7

    6

    8

    5

    9

    7

    0

    P1 3 4
    P2 2 4
    P3 1 3
    P4 1 4

If you want to avoid the use of Dial-Plan you can set a function key as speed dial type and fill with the number to dial

In order to simulate the function key button you need to short circuit the two pins according to the Keyboard Matrix
This will start the calls immediately. [See example 3]  



Example 1

If you short-circuit the contacts 2 and 3 of the KBD connector you are simulating the pressure of the Key Number 0,
so adding a regex dialplan like the following you will be able to automatically call speed dial associated from key 0 to 9: 

!([0-9]+)!sip:\1@\d!d


Example 2

If you short-circuit the contacts 2 and 3 of the KBD connector you are simulating the pressure of the Key Number 0,
so adding a regex dialplan like the following you will be able to automatically call the extension 108:

You need to add the number to call in the string. 

|^1$|sip:108@\d|d


Example 3

If you short-circuit the contacts 2 and 4 of the KBD connector you are simulating the pressure of the P2 key, 

this will dial the number that you put into the label (in this case extension 108)

There's no need of a dial-plan. 


More info on wiki: