[. . . ] [. . . ] These screws are solely for mechanical protection during transport, they don't serve any further purpose. If the unit doesn't work please make sure to check the wiring and the fuse that's located on the back of the unit. Basic operation: Press any button (except 7 and 4) to switch the unit on. Please refer to the operation manual for a more detailed description about the units functions. [. . . ] [. . . ]