The Foxboro Company

Other

Codenoll Technology Corporation

Triconex Corporation

Nathan H Tobol

Simon Korowitz

Frederick W Scholl

William M Slechta

Michael H Hilford

Melvin G Oster

M Charles Cheney

Thomas Michael Schurman

Walter B Hatfield, Jr

A process and apparatus for performing a ground fault test of a device is disclosed. A current level may be selected from a plurality of predetermined current levels. A ground fault current may be generated between a first power line and a ground at the selected current level until a ground fault interrupter within the device trips, or until expiration of an on-time period associated with the selected current level. The ground fault current may then be set to zero for an off-time period associated with the selected current level. The process may be repeated for each of the plurality of current levels. When the ground fault interrupter within the device trips, the current level and a time interval from an onset of the ground fault current at the selected level and a time when the ground fault interrupter tripped may be recorded.

Plug-in electric vehicle charger validation and test device

A method for transmitting messages between a communications controller and devices in a factory process control system, wherein each device has an associated identification number which is unique to that device. A message to be transmitted is compiled, and then based on the criticality of the message, one of a standard, secure, or critical message protocols is chosen for the message; each protocol being defined to generate a message checksum for the message in a manner different from the other protocols. The generated checksum is then included in the message. Using the secure and critical protocols, a message checksum is generated from the message to be transmitted and the identification number of the intended recipient device. In the secure protocol, the message checksum is included in the message, but the identification number is not included in the message; in the critical protocol, both the message checksum and the identification number are included in the message. A crosstalk query message may be sent from the controller to determine if a link of a factory process control system is susceptible to crosstalk. The controller sends to a link on which a particular device is known to reside a diagnostic message indicating the identification number of the particular device and requesting any other devices that unintentionally receive the message to transmit a response message to the communications controller.

Protection against communications crosstalk in a factory process control

A token passing media access protocol provides distributed time scheduling. The token provides an indication of each time at which a network device is to perform a cyclic or time critical operation. The token also provides an indication of system time to enable all devices on the network bus to be synchronized. The format of data transmissions on the network bus employs a shortened device address when referencing the device as a source. The source address corresponds to a unique portion of the device address.

Token device for distributed time scheduling in a data processing system

A multiple pin block having a distinct electrically readable pin pattern and a corresponding visually readable label is useful as an identifier for electronic modules and other elements in electrical networks. Differing blocks each with identifiable labels, and corresponding electrical pin patterns may be inserted in devices to identify and distinguish the differing network modules or lines and thereby facilitate assembly, maintenance, testing and operation.

Identity insert block for electronic modules

Through the method and apparatus of the present invention the collision of two packets can be detected with a high degree of accuracy under a variety of conditions. The preamble of each packet transmitted is modified to include collision detection data comprising an initial pulse having an amplitude sufficiently high to be detected even when attenuated and having a pulse width twice the normal data pulse width followed by a transceiver code of a predetermined length unique to each transceiver. Thus, in the event two packets collide, the collision may be detected by recognizing a second large pulse within a time period less than the sum of the packet duration and the gap between packets, by determining if a large initial pulse has a pulse width larger than the generated pulse width, and by determining if the transceiver code echoed back to the transmitting transceiver is equal to transceiver code stored in memory on the transceiver. If a transceiver detects a collision, a large collision detect pulse having an amplitude and pulse width similar to the amplitude and pulse width of the large initial pulse is transmitted within the time period less than the sum of the packet duration and interpacket gap, thus assuring that the collision is detected by all transceivers.

Method and apparatus for detecting the collision of data packets

A majority-voted output circuit generates an output parameter which is the majority vote of its input parameters by series-parallel combination of four intermediate switches, each said switch being a Boolean function of the input parameters, and the circuit being arranged so that failure of any one switch does not affect the value of the output parameter. Alternate embodiments are provided which use 'don't care' signals to allow the majority vote of less than the full complement of input parameters. The majority-voted output circuit is subjected to testing by stepped transitions of its input parameters (to test for failure of any of the four intermediate switches) and by forcing current flow through predetermined current paths (to test for failure of a particular electrical connection).

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Wrentham, MA, United States of America

Nathan H Tobol