I want to know exactly the same thing.. ive tried
3CXVoIPClient.exe call [number]
which sort of works but is unusable because the phone number winds up getting corrupted.
It will try to dial out to a number, but 2 or 3 random digits from the ph no don't wind up getting entered in before dialing, rendering it useless.
This software is quite good and i want to integrate it with the custom CRM i'm developing, but i can't find any resources on this topic, which is annoying, because they MUST be there somewhere.
Alternatively, is there some sort of TCP/IP protocol controlling the dialer?