Abstract: In a sequence-of-events system for a distributed process control system, unfiltered changes in process element status are initially stored at each remote site along with a time tag. Each remote site has an I/O manager board to which are connected a number of individual I/O boards. Each I/O board in turn has connected to it process signal inputs from a number of process elements (e.g., 16), which can be in an "on" or "off" state. Each I/O board includes a change-of-state detector to which the process signal inputs are coupled. The change-of-state detector detects a change of state of any process input and generates an interrupt signal, which is coupled to a microprocessor also located on the I/O board. The microprocessor reads the status of all the process element inputs coupled to the scanner and also the output of a local clock on the I/O board.

Abstract: In a triac power switching system, two triacs are connected in series between an AC power source and a load. Each time power is applied to a load, the triacs are tested by first turning on one of the triacs while maintaining the other triac turned off, then turning on both triacs to apply power to the load for a set time interval and then turning off one of the triacs and determining whether power is still applied to the load. If power is applied to the load while either one of the triacs is supposed to be off, an alarm is sounded. In addition, if power is not applied to the load when both triacs are turned on, an alarm is sounded.

Abstract: In an industrial process control system, in which a plurality of remote stations interconnected by a communications link each control and manage a plurality of input/output devices, each remote station comprises a primary data processor and a back-up data processor. The primary data processor normally exercises control over and manages the input/output devices, but, should the primary data processor fail, the back-up processor takes over management and control of the input/output devices. Periodically, the primary data processor transfers status data relating to its operation in the control of the input/output devices to the back-up data processor via a dual ported memory connected between the two processors. The back-up processor maintains a record of the status data and updates its record of the status data with the periodically transferred copy of the status data.

Abstract: A combined mode program-panel controller method for a distributed industrial process control system permits a system operator to configure the overall system architecture to control the sequential operation of the entire system or a sub-portion thereof. The program-panel controller includes a first user accessible graphic program by which the system architecture can be symbolically reconfigured and a second user accessible instruction set program by which the operating parameters of the so-configured system or a sub-portion thereof may be altered.

Abstract: An industrial process control system in accordance with the present invention includes a plurality of device controllers connected together through a common buss with each device controller connected to an associated controlled device(s) that effect process control. A computer-aided system interface for controlling the overall system includes a visual display device in the form of a multi-color CRT and a graphic input device in the form of a transparent touch-responsive panel that overlies the CRT display screen. Computer generated symbols representing the controlled devices are displayed on the CRT screen to define touch-responsive target areas. When an appropriate target area is touched by a human operator, a signal, such as a command signal, is generated to cause the controlled device whose symbol is displayed in the designated target area to respond, with this response being then indicated by a change in the device symbol being displayed on the screen.

Abstract: An industrial process control system in accordance with the present invention includes a plurality of device controllers connected together through a common buss with each device controller connected to an associated controlled device(s) that effect process control. A computer-aided system interface for controlling the overall system includes a visual display device in the form of a multi-color CRT and a graphic input device in the form of a transparent touch-responsive panel that overlies the CRT display screen. Computer generated symbols representing the controlled devices are displayed on the CRT screen to define touch-responsive target areas. When an appropriate target area is touched by a human operator, a signal, such as a command signal, is generated to cause the controlled device whose symbol is displayed in the designated target area to respond, with this response being then indicated by a change in the device symbol being displayed on the screen.

Abstract: In a system employing a plurality of touch sensitive screens which generate analog signals representing the coordinates of a position touched, a selection means is provided to select the screens rapidly in sequence with the analog output signals from the selected screen being fed to analog-to-digital converters. The sequence of selection proceeds rapidly from screen to screen until it is detected that a screen has been touched whereupon the selection sequencing pauses to permit the analog-to-digital conversion to be carried out and the resulting digital values to be read out to a computer system. Upon readout of the digital values to the computer system, the screen selection sequencing is again permitted to proceed. Means are provided to indicate whether a selected screen that is being touched was touched the last time the same screen was selected.

Abstract: A control system for controlling an industrial process includes a plurality of remotely located process control units (remotes) each coupled to an associated input/output device(s) and adapted to communicate with one another through a dual channel communications link. Each remote has a unique succession number within a predetermined succession order with supervisory communication-control of the communication link sequentially transferred to each remote according to its succession number to provide a revolving or master for the moment control of the system. Digital information in the form of data and control information blocks is transmitted between the remotes with the blocks transmitted twice on each channel of the communications link.

Abstract: In an industrial control system, a plurality of remote data processing units communicate with one another over a communications link. Some of the processing units called primary remotes have inputs and outputs and control a process operation in response to signals received on the inputs by signals transmitted over the outputs. One or more of the remote processing units, referred to as a redundant remote, monitors a plurality of the other primary remotes to determine whether any of the monitored primary remotes has failed. If any of the primary remotes fails, the redundant remote takes over operation of the process controlled by the failed primary remote by sending instructions and commands over the communications link interconnecting the primary and redundant remotes.