Allen-bradley Company, LLC

Irwin International, Inc.

Bruce Graham

Juan F Velazquez

Francis Lum

Samuel N Irwin

Joseph David Purcell

Data is sent over a digital communication network in a message frame which includes a header, a data field and an end delimiter. An analyzer for such a network evaluates the response of network interface devices to test message frames. Included in the analyzer is a mechanism for creating a test message frame which allows the user to define a number of pad-idle symbols, a sequence of symbols for a start delimiter, a series of symbols for the data field and a set of symbols for the end delimiter. The use defined test message frame may include invalid symbols to test the error response of the interface device. A transmitter is provided for repeatedly sending the test message frame to the network interface device with a given number of silence symbols inserted between each repetition. The analyzer has a section for receiving message frames back from the network interface device and sequentially comparing the symbols of the test message frame to those of the received message frame. A count is maintained of the number of received message frames which do not coincide with the test message frame.

Communication network interface testing system

A method for positioning and maintaining a disc head over a desired track centerline on a disc rotatably carried on a disc drive. The distance between the current position of the disc head and the desired track centerline is monitored, and a signal generally proportional to that distance is applied to the disc head moving mechanism to cause the disc head to move toward the track centerline. The control signal is clipped if it exceeds predetermined maximum and minimum values.

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Ypsilanti, MI, United States of America

Bruce Graham