Those are 2 different things, although you can use them together.
The
Call Control API is a .NET Core API, you use it from C# code.
The Call Flow Designer is a graphical tool to create callflows and voice apps. You can use it to create callflows or dialer:
- Callflows: these are visual flows to handle inbound calls. You deploy the callflow to a queue extension, and then you route inbound calls to this extension, so the callflow can handle it. This callflow can be used to perform intelligent routing, to play wav files to the caller, to present menus where the user needs to enter a DTMF option, etc.
- Dialers: these are visual flows to trigger new calls. You usually use them to make calls between an internal extension and an external party.
The CFD has many standard building blocks out of the box, which let you access databases, execute web services, etc. without programming. It also lets you execute C# code, and there you can invoke methods from the Call Control API...
Here you have useful links for the CFD:
https://www.3cx.com/docs/manual/call-flow-designer-manual/
https://www.3cx.com/docs/manual/call-flow-designer-manual/
Kind regards.