An access control system comprising: a control panel; one or more door locks (24, 34); and a multi-output power supply including: an input power port of the multi-output power supply for receiving input power; a first output power port of the power supply configured to supply a first voltage derived from the input power received from the input power port; and a second output power port of the power supply configured to supply a second voltage derived from the input power received from the input power port, characterised by the first output power port being arranged to provide power to the control panel and the second output power port being arranged to provide power to the one or more door locks, and the multi-output power supply further including a shut-down circuit configured to shut down one of the first or second output power ports independently of the other of the first or the second output power ports, if power drawn from the one shut down output power port exceeds a first predetermined value, wherein the shut-down circuit is further configured to shut down one of the first or second output power ports if a total power exceeds a maximum power for a power overcurrent time and to shut down the other of the first or second output power ports if the shutting down of the one shut down output power port, when the total power exceeds the maximum power, does not reduce the total power below the maximum power, the total power being the sum of the power of the first and second output power ports. a control panel; one or more door locks (24, 34); and a multi-output power supply including: an input power port of the multi-output power supply for receiving input power; a first output power port of the power supply configured to supply a first voltage derived from the input power received from the input power port; and a second output power port of the power supply configured to supply a second voltage derived from the input power received from the input power port, characterised by the first output power port being arranged to provide power to the control panel and the second output power port being arranged to provide power to the one or more door locks, and the multi-output power supply further including a shut-down circuit configured to shut down one of the first or second output power ports independently of the other of the first or the second output power ports, if power drawn from the one shut down output power port exceeds a first predetermined value, wherein the shut-down circuit is further configured to shut down one of the first or second output power ports if a total power exceeds a maximum power for a power overcurrent time and to shut down the other of the first or second output power ports if the shutting down of the one shut down output power port, when the total power exceeds the maximum power, does not reduce the total power below the maximum power, the total power being the sum of the power of the first and second output power ports. an input power port of the multi-output power supply for receiving input power; a first output power port of the power supply configured to supply a first voltage derived from the input power received from the input power port; and a second output power port of the power supply configured to supply a second voltage derived from the input power received from the input power port, characterised by the first output power port being arranged to provide power to the control panel and the second output power port being arranged to provide power to the one or more door locks, and the multi-output power supply further including a shut-down circuit configured to shut down one of the first or second output power ports independently of the other of the first or the second output power ports, if power drawn from the one shut down output power port exceeds a first predetermined value, wherein the shut-down circuit is further configured to shut down one of the first or second output power ports if a total power exceeds a maximum power for a power overcurrent time and to shut down the other of the first or second output power ports if the shutting down of the one shut down output power port, when the total power exceeds the maximum power, does not reduce the total power below the maximum power, the total power being the sum of the power of the first and second output power ports.