Abstract: A computer system in a fault-tolerant configuration employs three identical CPUs executing the same instruction stream, with two identical, self-checking memory modules storing duplicates of the same data. Memory references by the three CPUs are made by three separate busses connected to three separate ports of each of the two memory modules. The three CPUs are loosely synchronized, as by detecting events such as memory references and stalling any CPU ahead of others until all execute the function simultaneously; interrupts can be synchronized by ensuring that all three CPUs implement the interrupt at the same point in their instruction stream. Memory references via the separate CPU-to-memory busses are voted at the three separate ports of each of the memory modules. I/O functions are implemented using two identical I/O busses, each of which is separately coupled to only one of the memory modules. A number of I/O processors are coupled to both I/O busses.

Abstract: A computer system in a fault-tolerant configuration employs three identical CPUs executing the same instruction stream, with two identical, self-checking memory modules storing duplicates of the same data. Memory references by the three CPUs are made by three separate busses connected to three separate ports of each of the two memory modules. The three CPUs are loosely synchronized, as by detecting events such as memory references and stalling any CPU ahead of others until all execute the function simultaneously; interrupts can be synchronized by ensuring that all three CPUs implement the interrupt at the same point in their instruction stream. Memory references via the separate CPU-to-memory busses are voted at the three separate ports of each of the memory modules. Each CPU has a local memory, separate from the memory modules, and this local memory is of the dynamic type so it must be periodically refreshed.

Abstract: A device and process for measuring cervical range of motion about three axes comprises a frame which is supported on the nose of a subject and which has side temple pieces for locating the frame on the wearer's head. Cervical range of motion of a wearer's head can be measured through the use of gravity type angle meters and a magnetic type angle meter which are mounted on the frames and easily referenced back to the frame. The magnetic type angle meter is mounted above the head on a removable arm, which is supported on the frame. A magnetic field is created using magnets mounted on the subject to obtain reliable head rotation readings. The magnetic type angle meter can be removed, and an arm which is mounted on the frame and extends above the head of a wearer and which when coupled with a locator arm can determine a forward head position measurement.

Abstract: A device and process for measuring cervical range of motion about three axes comprises an eyeglass frame which is supported on the nose and ears of a patient. A pendulum angle finder and a compass and the pendulum is mounted a horizontal axis and the compass needle is mounted about a vertical axis. The angle finder and compass are mounted on the eyeglass frame with a clamp that permits rotating the angle finder 90.degree. to permit measuring angles about two mutually perpendicular axes in the horizontal plane to permit tri-planar angle measurements. The angle finder and compass can be adjusted to a zero position and cervical range of motion is then measured through the use of angle indictor scales provided on the angle finder and compass. Readings may be made about one, two, or all three axes of rotation.