Desktop computer power supplies convert alternating current (AC) to direct current (DC), needed for the computer. Standard box units for computer power supplies are defined with industry-standard names, for instance, ATX, FlexATX, microATX, AT, LPX, NLX, SFX and TFX. There are a variety of computer motherboard styles and cases available. Most case styles have a corresponding power supply type. Common choices for DC output voltage include +/- 3.3 V, +/- 5 V, +/- 12 V, +/- 15 V, +/- 24 V and +/- 48 V. The number of outputs, DC output current and power are also important to consider. The DC output current is the output current corresponding to the primary DC voltage output. AC inputs include input voltage and input frequency. Choices for input voltage include 115 VAC and 230 VAC. Input frequencies for computer power supplies can be 50 Hz, 60 Hz, or 400 Hz.