First of all it is the Bluetooth accessory for our range of inverter/chargers: Multis, Multi Plusses, Multi Plus-II, Multi Grid, Multi  Grid-II, Quattros, and our series of Phoenix Inverters with a VE.Bus port. When installed, use the Victron Connect App to monitor operation and also operate the system: change the input current limit as well as switch between Off, On and Charger-only modes.