An apparatus for moving a closing barrier, in particular for moving a door or a gate, the apparatus comprising: - a control station comprising a supply circuit for supplying a Pulse-Width Modulated, PWM, supply voltage to a two-wire communication and supply bus that is coupled to said control station; and - at least one utilizer device configured to use said PWM supply voltage and is coupled to said two-wire communication and supply bus, said utilizer device comprising a conversion circuit for converting said PWM supply voltage into a supply current for an electric motor for movement of said closing barrier, wherein said control station further comprises an amplitude modulation circuit for transmitting an amplitude-modulated data communication signal superimposed on said PWM supply voltage onto said communication and supply bus, wherein said amplitude modulation circuit comprises a circuit for generating a carrier signal and a circuit for amplitude modulation of said carrier signal, which is coupled the generator circuit, in that said at least one utilizer device that is configured to use said PWM supply voltage is coupled to a circuit for amplitude demodulation of said amplitude-modulated data communication signal for receiving signals from said communication and supply bus, wherein said signals received at said utilizer device from said communication and supply bus comprise commands for moving said closing barrier; the apparatus is characterized in that: - said supply circuit for supplying said PWM supply voltage and said conversion circuit for converting said PWM supply voltage are coupled to the communication and supply bus via respective choke filters (1002; 1202); and - said amplitude demodulation circuit (124; 142'; 104) comprises a band-pass filter having a central frequency equal to the frequency of said carrier signal, an envelope-detector circuit and a discriminating and squaring circuit. - a control station comprising a supply circuit for supplying a Pulse-Width Modulated, PWM, supply voltage to a two-wire communication and supply bus that is coupled to said control station; and - at least one utilizer device configured to use said PWM supply voltage and is coupled to said two-wire communication and supply bus, said utilizer device wherein said control station further comprises an amplitude modulation circuit for transmitting an amplitude-modulated data communication signal superimposed on said PWM supply voltage onto said communication and supply bus, wherein said amplitude modulation circuit comprises a circuit for generating a carrier signal and a circuit for amplitude modulation of said carrier signal, which is coupled the generator circuit, in that said at least one utilizer device that is configured to use said PWM supply voltage is coupled to a circuit for amplitude demodulation of said amplitude-modulated data communication signal for receiving signals from said communication and supply bus, wherein said signals received at said utilizer device from said communication and supply bus comprise commands for moving said closing barrier; the apparatus is characterized in that: - said supply circuit for supplying said PWM supply voltage and said conversion circuit for converting said PWM supply voltage are coupled to the communication and supply bus via respective choke filters (1002; 1202); and - said amplitude demodulation circuit (124; 142'; 104) comprises a band-pass filter having a central frequency equal to the frequency of said carrier signal, an envelope-detector circuit and a discriminating and squaring circuit. - said supply circuit for supplying said PWM supply voltage and said conversion circuit for converting said PWM supply voltage are coupled to the communication and supply bus via respective choke filters (1002; 1202); and - said amplitude demodulation circuit (124; 142'; 104) comprises a band-pass filter having a central frequency equal to the frequency of said carrier signal, an envelope-detector circuit and a discriminating and squaring circuit.