Abstract: Apparatus is connected by way of a serial communication link to at least one computer-based elevator controller in order to monitor the diagnostic output of each connected controller. The diagnostic output of a controller is determined in a manner by which the elevator system is modeled as normally operating sequentially from state to state in a closed loop sequence of linked operating states. Any deviations from this sequence generate diagnostic messages that are communicated from the controller to the monitoring apparatus. Also communicated are the last to occur of a plurality of parameter signal state changes. The monitoring apparatus processes the diagnostic signals for visual and/or hard copy display to interested elevator personnel in a meaningful way. Further, the monitoring apparatus provides a plurality of signals to the elevator controller indicative of corresponding reference standards that the elevator controller utilizes in determining the occurrence of certain elevator event conditions.

Abstract: An elevator monitoring apparatus and method are disclosed in which an elevator is modeled as operating in a closed loop chain of normal operating states from which message initiating transitions to abnormal states causes the latest to occur of a selected number of monitored events are recovered from a storage buffer as an aid to an analysis of an abnormal state. Door and motion closed loop chain state machines are disclosed as effective tools for abnormal event detection, especially for a state machine approach implemented within an elevator controller.

Abstract: A serial signal communications system includes a central station unit connected through a balanced impedance signal communication bus to one or more remote station units.

Abstract: An elevator control system wherein signals between fixtures and the controller are provided in time-division, half-duplex multiplexing protocol is disclosed. Remote stations (64, 150) serialize multiple fixture inputs (66-69) and outputs (106-109) and are characterized for response during particular time slots by binary address means (84). A master station (90) serializes multiple controller inputs (102-105) and outputs (93-96) and is responsive for all time slots in either a transmit or receive mode. A portion (82) of the controller (78) provides clocking (76) and dynamic addressing (98) for the system.