Abstract: A first local controller (30) having a device port coupled to a device control port for communicating with a device to be monitored or controlled, a primary local port for coupling to a first interface port (90) of an interface unit, and a secondary local port.

Abstract: In a push-pull-connected final stage (111) of an audio amplifier, its two supply poles (117, 118) are supplied by low-impedance current sources, the voltages of which comprise, in principle, a constant positive voltage and a constant negative voltage superimposed by the input signal to the final stage. Each of these voltages is obtained by a respective pulse-width modulated amplifier (103, 104) coacting with lowpass filter circuits (109, 110) and recovery diodes (107, 108). Distortion factors which are thirty times better than the distortion factors obtained with conventional class D-amplifiers with pulse-width modulation can be achieved.