The buttons are to do with record enabling or monitoring I would have thought. The supplied mics probably run off 'plug in power', low voltage not phantom (24 or 48 volts). I could be wrong about this but it is odd that phantom doesn't get a mention anywhere - eg in relation to battery life - nor is there evidence of a physical switch which is the normal arrangement. And given the theoretical hazards involved in making connections with phantom on, there's usually a well labelled method of turning it off and on, and, as far as I'm aware, it's not usually a menu function.