A printing and display device for use with an external computer. In one or more embodiments, the present disclosure relates to an expandable interbody spacer. The positioner operating mode identifying function identifies the operating mode of a positioner or from the direction of change of a control output and the direction of change of an amplified pneumatic pressure signal Pout, and the identification result is set automatically as the current operating mode of the positioner. A significant improvement in the efficiency of a power amplifier is achieved by the combination of the voltage supplied by means of a DCDC converter for the amplifiers with distributed power gain.