A keyboard apparatus in which the radius of turning motion of a mainly operated portion of each black key in a key depressingreleasing direction is maximized so as to enhance the operability of the black key for performance. In this case, the result of the comparison between the load current and the maximum value is only taken into consideration within at least one time window during at least one timing period of the switching pulses. The secure CDN may be a dedicated network or a subset of a larger distributed network that is managed by the service provider. A third user selection of an inset definition from the set of inset definitions is received. The pin is detachable from the via and the contact element deforms upon insertion of the pin. The level control system makes it possible that the pump has to always run only in one direction.