Abstract: An interface circuit for use between an input circuit and an industrial automation system is disclosed. The industrial automation system includes an opto-coupler capable of being operably connected to the interface circuit. The interface circuit includes a first and second terminal, each terminal capable of being operably connected to the opto-coupler. A first current-source is operably connected to the first terminal and a second current-source is operably connected to the second terminal. A reference voltage is operably connected to the first current-source and the second current-source wherein the first and second current-source cooperate to provide a total input current in accordance with the operating characteristics of the industrial automation circuit.

Abstract: A system having a redundant topology for communication between one or more devices and a central hub. The system comprises a central hub or switch and one or more end nodes where each end node includes a first port and a second port. A first active cable is connected to the first port in each end node and a first port in the hub and, a second active cable is connected to the second port in each end node and a second port in the hub. Messages are transmitted across both the first and second cables to the first and second ports of the end nodes. The end node performs an integrity check on the messages received over the first and second cables and utilizes the first one to pass the check. Thus, if one cable malfunctions, the end node still is able to receive the message over the other cable without any loss of data.

Abstract: A control system includes an Internet web interface to a network of at least one programmable logic control system running an application program for controlling output devices in response to status of input devices. The Web interface runs Web pages from an Ethernet board coupled directly to the PLC back plane and includes an HTTP protocol interpreter, a PLC back plane driver, a TCP/IP stack, and an Ethernet board kernel. The Web interface provides access to the PLC back plane by a user at a remote location through the Internet. The interface translates the industry standard Ethernet, TCP/IP and HTTP protocols used on the Internet into data recognizable to the PLC. Using this interface, the user can retrieve all pertinent data regarding the operation of the programmable logic controller system.