Abstract: A Local Area Network consists of a number of stations connected together by a transmission line, each station having a transmitter and a receiver. A transmitter generates a sequence of information signals having individual message portions separated from one another by flag signals, each message portion having a predetermined number of symbols. A receiver processes a message portion by analyzing the content of each section formed by dividing the message portion into the predetermined number of equal parts. The receiver includes stores and, a detector, a signal-divider and a unit which determines a representative value.

Abstract: In a variant of the type of radiographic apparatus known as CT scanners a scanning X-ray tube is used to provide a planar fan-shaped distribution and to scan the distribution in its plane. Means are also provided to rotate the system about an axis perpendicular to the plane. In order to properly relate operation of the system, it is desirable to monitor the progress of the tube scan. This invention disposes a detector into the radiation and a pair of gratings acting together to modulate the radiation, incident on the detector, in relation to the scan position. The detector output is processed to give pulses which can be used to regulate the tube scan.

Abstract: An electrical power supply for an X-ray tube has a source capable of providing constant current at a desired potential to a capacitor means which supplies pulses of current in excess of the source current to the X-ray tube. As each pulse is supplied, the potential at the output of the supply tends to drop. One side of the capacitor means is connected to the output. A compensator is connected to the other side of the capacitor means and responds to a drop in the output potential to apply to the other side of the capacitor means a voltage which maintains the output voltage constant.

Abstract: In radiographic apparatus in which a source of radiation and detectors receiving the radiation are orbited about a position for locating a patient, the examination can be carried out using a rotation through 360.degree. or more. This arrangement uses slip rings for carrying data, including the output of the detectors and provides a slip ring arrangement suitable for high speed use. The slip rings can have capacitative coupling to avoid data loss if the brushes are allowed to bounce and for use therewith the data should be encoded in a D.C.-component-removing digital code.