I am using 3cx version 11 on my machine. On version 11 they provide the api for making up the calls from your client machine to destination. There is no need to configure the devices, we just need to use the following URLto generate the calls:
http://:5000/ivr/PbxAPI.aspx?func=make_call&from=&to=&pin=
where pbx is the ip of the machine which got the 3cx. Click here! for more info about the api.
As you can see it is mention on their website that this api is not available on version 12. I need to ask that is there any alternative to generate the calls if some one is using version 12? Because most of the users now are using version 12, and as an admin I need to figure it out that how can I provide this facility to my clients who have installed version 12.