The second option to communicate in the row of communication buttons is the Call from Phone. When you click this button, the desk phone instantly starts ringing and the call is established from your desk phone. This depends on your service provider configuration as other devices may also ring.
For remote calls initiated using Communicator, you can also have mid-call controls such as hold/resume, transfer, and add participant.
Depending on your service provider settings, it is also possible to control calls initiated without Communicator in the Active Communications view. The same mid-call controls are also available in this case. In case of an incoming call, the actual answering action must happen with the other device.