Within Recruitis ATS, phone numbers are "clickable". This means that when you click on a phone number, you are offered the option to call that number using a native service on your computer (e.g., using FaceTime on Apple).
Now, if you have an active mobile application, clicking on a phone number in the desktop application, i.e., on a candidate card or in the candidate database, will trigger a notification on the paired mobile device with the app, and you can then call the candidate directly from your phone.
See how simply it all works in the video below: