Some hardware types can report back to JMRI the track volatage and current being consumed.
The displayed Meter is selectable via the Voltage meters and Current meters menus.
The settings menu contains options to edit the unit display options ( eg. Volt, Millivolt ), along with the number of whole numbers and decimal places.
The Voltage / Current Meter can be opened from the JMRI Tools Menu.
To swtich track power on and off, see the Power Control.