Patent ID: 7707458

Claim:
An electronic system comprising a system to be monitored having a plurality of output signals, a plurality of fault-monitoring devices each of which is adapted to have a respective first input from the system to be monitored and an output for outputting a fault signal when a respective first input indicates that the system to be monitored is in a fault condition, wherein: the fault-monitoring devices are arranged in a cascade fashion, a fault-monitoring device having a second input connected to the output of a preceding fault-monitoring device; the electronic system being adapted to induce a fault-monitoring device of the cascade to output a fault signal, which signal is cascaded as an input to the second input of a subsequent fault-monitoring device; the electronic system being arranged to determine whether there is a fault with a fault- monitoring device by being arranged to create a record of a fault from the output of the final fault-monitoring device, the absence of a record being created when the electronic system induces a fault signal output signifying a fault in one of the fault-monitoring devices; wherein a first fault-monitoring device is adapted to output a fault signal when the electronic system is placed into a switched-off condition; and wherein the electronic system is associated with a vehicle and the electronic system is placed into a switched-off condition by turning an ignition key.