Abstract: A computerized system is of the type that responds to imminent loss of power by storing crucial data to a safe storage area. In the system, lockup caused by the system entering a tight loop awaiting power loss, is avoided by a combination of stored program and hardware. A test performed in the tight loop checks repeatedly to see whether the power-failure signal comes no longer to be present, and if that condition occurs the stored program causes the meter to return to normal function. As a consequence momentary power losses and other brief interruptions, whether due to user manipulation of the power switch or otherwise, are much less likely to result in undesired lockup of the system.

Abstract: A system for identifying faults in an electrical circuit such as a circuit of a road vehicle. The electrical circuit is intended to provide a plurality of outputs such as lamp illumination in response to predetermined circuit conditions. Data describing individual components of the electrical circuit and the interconnections therebetween is stored. Data identifying a fault symptom is input to the system by a technician to indicate that for one said predetermined set of circuit conditions the intended output is not provided. Stored data is accessed which describes selected components which if faulty could be the cause of the fault symptom. Values of electrical variables to be expected at predetermined measurement points in a sub-circuit defined by the selected components and the connections therebetween are calculated.