A portable power supply capable of furnishing up to 2500 volts at ten microamperes is described. An input of 45 volts at 3 milliamperes gives 600 volts output with a constancy equal that of the driving battery. The weight including the 600‐volt output condenser but excluding batteries is 450 grams. A modification requiring a 90‐volt supply and weighing 175 grams is discussed. Possible additional uses such as pulse generator, counting‐rate‐meter and ignitron control are mentioned.