Personal study notes of Ryan. PLEASE NOTE: I do NOT claim that these notes are accurate. They are for my own personal study. Using an analogy: Voltage is similiar to water pressure Amperage is similiar to the speed of water flow. US power is nominally 115 volts and 60hz Computer power supplies usually supply -5, +5, -12, +12 voltages. They also supply a "power good" signal to let the motherboard know that everything is working right. In general, PC power supply fans are exhaust fans. They blow outward and suck air from inside of the computer. In AT Power Supplies, the black cord that runs from the power supply to the power switch usually has 4 wires and 4 spade connectors: Back to our homepage