US Patent 7659726 Image forming apparatus with plural AC sources

An image forming apparatus includes two AC power input cords to be connected to an AC power source. The image forming apparatus can detect if at least one of the two AC power input cords is not connected to the AC power source. An input voltage detector or a zero-cross signal detector receives an input from the one AC input power cord, and detects a voltage state of connection to the AC power input cord. A controller utilizes signals from the input voltage detector or zero-cross signal detector to detect whether the one AC input power cord is connected to the AC power source. An operator can also be provided an indication if it is determined that the one AC power input cord is not connected to the AC power source.