A power supply comprises a chassis, a plurality of alternating current power receptacles formed into the chassis, and power supply circuit contained within the chassis and selectively coupled to ones of the plurality of AC power receptacles. The private network also typically includes a local area network and the private network typically connects to the public networks using the wired-packet protocol, such as IP. The chad recoverydelivery unit delivers a chad perforated by the perforating unit to the chad storage unit via discharge channels in the chad guiding unit. The unloading apparatus includes a scissor mechanism to raise andor lower tire racks to an unloading platform. The sense circuit can thereby operate at a relatively wide common-mode voltage range, and utilizes a lower power supply voltage. The heat sink includes a body with a cavity, a number of fins radiating outwards from the body, and a cover plate covering the fins.