Ubiquiti UVP-Pro UniFi - Call Management Features; In-Call Controls and Status

Call Manager
Volume
Slider
Connected
Number
Connection
Status
Connected Number Displays the extension or phone number
that is being dialed or that is currently connected.
Volume Slider Use the slider to increase or decrease the
volume level.
Connection Status Displays “Dialing” or the total elapsed
time of the currently connected call.