Abstract: An apparatus provides hot standby operation with normal and standby processors, each of which includes vital inputs electrically interconnected with the vital inputs of the other processor, vital outputs, and an application routine inputting the vital inputs and outputting the vital outputs. Communication ports communicate with communication ports of the other processor. A health routine provides a health status after communication is established with the other processor. A vital relay includes an input controlled by a vital output and an output to a vital input of the other processor. A synchronization routine provides a synchronization status through the communication ports. The application routine outputs the vital outputs when the synchronization status is set. The standby processor includes a reset routine, which resets the standby processor when the health status of that processor is not provided. A vital “OR” circuit outputs from the vital outputs of the normal and standby processors.