Abstract: Logic circuitry for use in electrical apparatus for providing an interrupt signal to a controller when there is a power failure in the electrical apparatus. The logic circuitry is connected to a bus from the controller. When the logic circuitry receives a power failure signal, it sets an interrupt state register and provides an interrupt signal on the bus as long as the interrupt state register is set. If the power failure signal no longer indicates a power failure, the logic circuitry responds to a signal from the controller indicating that the interrupt has been received by resetting the interrupt state register, thereby ending the interrupt. However, if the power failure signal is still active, the logic circuitry will not reset the interrupt state register in response to the signal from the controller.