The second one is used for NAV. there's also a standby freqency and a switch button. The right button is used to toggle ADF and transponder code while the left button is used to toggle NAV1 an NAV2 freqency.
Push buttons and toggle buttons
I have a 2 GF-T8 (toggle buttons) modules and 1 GF-P8 (pushbuttons) module. I assig lightning, parking brake, BATT, ALT, IGN, etc to those buttons. In the next version I will duplicate the switched on the lower panels from the 1900D. To that effect, I will use a Hagstrom key encoder (36 keys)
I use them to control the effis system. I can increase/decrease the range, the decision heigt, lower or raise the horizon on the attitude indicator. With the buttons I choose for arc or rose view, show or hide the CDI needle, toggle between VOR/ADF needles and show/hide airports, inetresections, Vor's and that kind of stuf. This happens through FSUIP, because GOFLIGHT doesn't support the Reality XP instruments.
I have integrated the Landing gear module in the lower part of the panel. That function will also be connected to the Hagstrom encoder in the future.
The modules that I will get back will be assigned to simulator functions like pause, slew, rate, etc.
The last module, but the best one is the MCP
It's the actual autopilot and it can be used for almost everything (except Vnav and Lnav). When not engaged, but with an altidude and a heading keyed in, it drives the flight director.