International Business Machines Corporation

Kenneth George Smith

John S Beeteson

David Sawdon

A display comprising a cathode ray display tube (1) having an electromagnetic deflection yoke (2) is described. A pair of first deflection coils (7,6) are located symmetrically about the longitudinal axis of the tube (1) on opposite sides of the yoke (2) for producing within the tube (1) a first magnetic deflection field. A pair of second deflection coils (8,20) are similarly located symmetrically about the longitudinal axis on opposite sides of the yoke (2) for producing within the lube (1) a second magnetic deflection field at right angles to the first deflection field. The display is further provided with a pair of first cancellation coils (4,3) connected to the first deflection coils (7,6) for producing a first cancellation field which tends to cancel a first stray field produced by the first deflection coils (7,6). Support means (10,11) secure the first cancellation coils symmetrically about the longitudinal axis. The display additionally comprises a pair of second cancellation coils (50,32) coupled to the second deflection coils (8,20) for producing a second cancellation field which tends to cancel a second stray field produced by the second deflection coils (8,20). Further support means (51,52) are provided for positioning the second cancellation coils (50,32) symmetrically about the longitudinal axis in such a way that a plane containing a second cancellation coil (50) is perpendicular to any plane containing a first cancellation coil (4). Preferably, the display also comprises control means (64) for generating a predetermined cancellation current in the second cancellation coils (50,32) in response to a particular second deflection current in the second deflection coils (8,20).

Cathode ray tube display with deflection yoke and radiation shield

A display comprising a cathode ray display tube (1) having an electromagnetic deflection yoke (2) is described. A pair of first deflection coils (7,6) are located symmetrically about the longitudinal axis of the tube (1) on opposite sides of the yoke (2) for producing within the tube (1) a first magnetic deflection field. A pair of second deflection coils (8,20) are similarly located symmetrically about the longitudinal axis on opposite sides of the yoke (2) for producing within the tube (1) a second magnetic deflection field at right angles to the first deflection field. The display is further provided with a pair of first cancellation coils (4,3) connected to the first deflection coils (7,6) for producing a first cancellation field which tends to cancel a first stray field produced by the first deflection coils (7,6). Support means (10,11) secure the first cancellation coils symmetrically about the longitudinal axis. The display additionally comprises a pair of second cancellation coils (50,32) coupled to the second deflection coils (8,20) for producing a second cancellation field which tends to cancel a second stray field produced by the second deflection coils (8,20). Further support means (51,52) are provided for positioning the second cancellation coils (50,32) symmetrically about the longitudinal axis in such a way that a plane containing a second cancellation coil (50) is perpendicular to any plane containing a first cancellation coil (4). Preferably, the display also comprises control means (64) for generating a predetermined cancellation current in the second cancellation coils (50,32) in response to a particular second deflection current in the second deflection coils (8,20).

Cathode ray tube display

An optical fibre communications link, for connecting a peripheral device to a computer system is presented, which includes circuit arrangement for generating a hybrid video signal, a device for transmitting such a signal along an optical fibre between the computer system and the peripheral device, characterized in that the transmitted video signal includes a reference pulse of predetermined amplitude, compensation devices for correcting changes in the characteristics of a received video signal which result from the optical communication link, and circuitry for using the reference pulse in a received video signal in order to control the compensation means.

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Eastleigh, United Kingdom

Kenneth George Smith