Call a device.

1. The Operator has to press the button from the Device and a popup menu will appear.

1. In the menu, the Operator can find two status:
   1. White Deivce name: Expert is connected. It is possible to call.
   2. Grey Device name: Expert is not connected. It is not possible to call

2. Finally, the Operator in the device called can decide to accept or decline the call.