Abstract: There is provided a power supply device 100 for switching power to an output line 150 between a first power supply 120 and a parallel second power supply 122. The power supply device 100 comprises: a first converter 130 connected to the first power supply 120 and configured to output a first voltage in a first predetermined range; and a second converter 132 connected to the second power supply 122 and configured to output a second voltage in a second predetermined range. The outputs of the first and second converters 130, 132 are connected together on the output line 150, and the first and second converters 130, 132 are arranged to maintain a voltage on the output line 150 within a third predetermined range.

Abstract: There is provided a power supply device 100 for switching power to an output line 150 between a first power supply 120 and a parallel second power supply 122. The power supply device 100 comprises: a first converter 130 connected to the first power supply 120 and configured to output a first voltage in a first predetermined range; and a second converter 132 connected to the second power supply 122 and configured to output a second voltage in a second predetermined range. The outputs of the first and second converters 130, 132 are connected together on the output line 150, and the first and second converters 130, 132 are arranged to maintain a voltage on the output line 150 within a third predetermined range.

Abstract: An apparatus and system for monitoring usage of one or more power tools, the system comprising setting means by which a prescribed extent of usage of a tool can be set. The prescribed extent of usage is determined by conversion of usage units into time units using a conversion function specific to said tool, wherein the conversion function is dependent upon operational characteristics of said tool. The apparatus or system further comprise sensing means for sensing usage of a tool, timing means for timing the duration of usage of the tool in accordance with said sensing means, and control means arranged to provide indication when the timed duration of usage of said tool reaches or exceeds the prescribed duration.