Abstract: Aircraft systems and sensors are monitored by pre-wiring a plurality of mating connectors to each system. Each mating connector has a positive voltage pin, a zero voltage pin and a reference pin. For those systems and sensors that emit zero voltage, the system is connected to the positive voltage pin while a jumper is used to connect the zero voltage pin to the reference voltage pin. For those systems emitting positive voltage, the system is connected with the zero voltage pin while a jumper is used to connect the positive voltage pin to the reference voltage pin. For each system or sensor monitored, there is a voltage comparator having both a positive and a negative input connected with a rear-mounted connector for connection with the pre-wired mating connectors. The rear-mounted connectors have identical pin arrangements with the mating connector for proper connections.