Abstract: A monitoring device is provided for use in association with a limit switch or similar mechanically actuated device in order to permit its end of life to be predicted. The system uses nonvolatile random access memory to store a count which represents the number of occurrences of one of two alternative events. The first event is the occurrence of a number of switch actuations and the second event is the lapse of a predetermined period of time. When either of these two events occurs, a microprocessor increments a count in the nonvolatile memory unit and clears both the clock and the volatile memory parameter. When the number stored in the nonvolatile memory represents a number of actuations estimated to be appropriately equal to the total life of the switch, this condition can be signaled to a sensor bus by a communication circuit. Alternatively, a light emitting diode can be alternately energized and de-energized to represent the number of actuations having exceeded the predicted end of life total.