The API 500VPR model is externally powered by a three-pole power supply and is designed to accept standard API 5.25" x 1.5" format modules. The 500VPR is internally wired for hot PIN 2 and comes with the L200PS API. The input/output jacks are both XLR. The 500VPR can hold up to ten PLC modules. API manufactures several modules suitable for this rack, including the 550A, 550b, 560, 525 and 512c. Like all API products, the 500VPR rack benefits from the standard API 5-year warranty.