The Click to Dial function allows you to dial a number directly from the GUI without needing to answer the call first from the phone. The phone starts the call as soon as you dial the number from the GUI. VOIspeed 6 uses the basic SIP standard REFER method for Click to Dial functionality. From the VOIspeed 6.4.15 version, the Call-Info method has been added to the PBX for IP phones that do not support REFER method.
Below are explanations for both methods:
REFER: REFER is standard SIP method which is also a default method that is used by the VOIspeed PBX sends the REFER method with the dialled number from the GUI to the phone which instructs the phone to dial the number. If your phone supports the REFER method then the phone must reply to PBX with SIP 202 Accepted message and then establish the call. Before the Phone sends the INVITE message it sends the NOTIFY message to the PBX which indicates that phone is going to call the number. The phone sends the INVITE message only after receiving the 200 OK reply from the PBX.
Call-Info: The Call-Info method has been added to VOIspeed versions after 6.4.15. This is not a SIP standard method but still it is used by many manufacturers. With this method the PBX sends an INVITE to the phone that contains the tag Call-Info: answer-after = 0 in the header message. If the phones support this message (e.g. Yealink phones) they accept the call from the GUI to quick-dial the number entered (without having the PBX calling back the phone before dialling).
Note: Some phones may take a few moments to accept the call and as a result you could hear the phone ringing in the meantime.
If your phone does not support any of the above methods then “Click to dial” and “Standard refer” available options will be unchecked under the Edit user agent section which you can see by going to Toolbox –>Devices. You can still call from the GUI but the call will require two different steps:
- Dial the number from the GUI which sends the call to the phone and phone will ring.
- Answer the call from the phone and only then will a number be dialled from the phone.