A decay is accomplished by applying a given voltage to the coil in order to decrease the current in the coil. Depending on the voltage that is applied, there are two types of decay. Using the equation U = l x dI/dt, it is shown that the higher the voltage is, the faster the current will increase or decrease. When a system recirculates the current in a high or low side of an H-bridge, a small voltage is applied to the coil, which is a slow decay. When the inverse of the DC bus is applied to the coil, the voltage is high, called fast decay.