The new power supplies pack as much as 1.2 kilowatts into a 19-inch, rack-mounted box that measures just 1U (1.75 inches) in height. Furthermore, these VSP Power Supply achieves an energy conversion efficiency of 80%, while keeping noise levels under 20 millivolts. Behind the performance advantages of the VSP series are advances in switching techniques. Two are particularly significant. One is soft switching; the other is a two-device asynchronous half-bridge DC to DC converter design. The soft switching technique is a vital step for reducing switching noise. This technique ensures that the switching action will occur when the voltage across the switching device is at a minimum. By turning the switching device in the converter on and off when there is little voltage across it, the transformer load does not see sharp voltage transients. Eliminating that transient gets rid of much of the high-frequency system noise that would otherwise propagate through the transformer to the output stage. It also helps reduce the noise that would typically feed back to the source. A built-in RFI filter further reduces conducted power line noise emissions, as well as susceptibility, allowing the supplies to meet EN55022 Class A standards. The VSP series further reduces the converter’s noise by using a "piggy pack" linear regulator to follow the conversion stage. The total effect is to improve the transient response to the changes in load and to reduce output noise and ripple from the DC converter to a maximum of 20 milli-volts, with 5 millivolts typical at full load. Along with controlling output noise, the converter and regulator allow the VS series devices to offer precise output voltage control.