The top black switch is the on/off for the Vibrato, the white "tea-cup" knob controls the Vibrato Intensity, and the lower white "chicken-head" regulates and switches the active circuit pre-amp in or out. The bank of three black switches adjacent to the Hofner rectangular control console are used to select the three pickups, either individually or in multiples.
A photo showing the complexities of the electric circuits.
The rotating cover adjacent to the strap button provides access to the active circuits' battery.