International Business Machines Corporation

David Leaver

Frederick S Jackson

Neil Wright-Boulton

Michael D Henry

John S Beeteson

Andrew Ramsey Knox

Mark W Hare

A cathode ray tube display having reduced electric field emissions comprising a cathode ray tube 100, an element 200 for detecting modulations in the final anode voltage of the CRT, the signal not being directly dependent on the deflection driving means 115. A matching network 205 provides phase and gain correction to the signal from element 200, amplification means 210 receives the signal from network 205 and an emission means 215 radiates a cancelling electric field dependent on the modulations detected by said element 200.

Cathode ray tube display with cancellation of electric field emissions

Cathode ray tube display apparatus includes a cathode ray tube having a screen (210) and a neck (350). In use an electron beam is directed from the neck (350) towards the screen (210) along an axis (S) of the cathode ray tube containing the centre of the screen (210). However, deflection means (320) mounted on the neck (350) deflects the beam from the axis (S) at a deflection centre (X) of the cathode ray tube to scan the beam across the screen (210) in a raster pattern. Raster rotation means (300, 310) permits rotation of the raster pattern about the centre of the screen (210). The raster rotation means (300, 310) includes first and second coils. The first coil (300) is located around the neck (350) at or near the deflection centre (X) to generate, in use, a first magnetic field in the path of the electron beam. The second coil (310) is parallel to the first coil (300) and located around the neck (350) on the side of the deflection centre (X) remote from the screen (210) to generate, in use, a second magnetic field, of opposite polarity to the first field, in the path of the electron beam.

Cathode ray tube display apparatus with rotatable raster

Synchronization apparatus comprising a phase-locked loop for generating an output signal and for synchronizing the output signal to an input signal, characterized in that the apparatus comprises a controller for iteratively determining whether the output signal is synchronized to the input signal by the phase-locked loop and adjusting the frequency of the output signal to bring the output signal within the capture range of the phase-locked loop if the output signal is not synchronized to the input signal.

Synchronization apparatus

An interrupt-driven processor system comprising a processor connected via a plurality of processor input and output lines to a keypad or keyboard. Actuation of one of the keys of the keypad or keyboard generates an interrupt signal on one of the input lines which invokes an interrupt service routine in the processor. A secondary interrupt source can be attached via an interrupt line to each of the input lines with the interrupt service routine being designed to discriminate between an interrupt signal generated by actuation of a key and an interrupt signal generated by a secondary source. Using this technique, further interrupts can be added to an off-the-shelf processor including keypad interrupts without the need for additional interrupt controlling hardware. Furthermore, a custom-built microprocessor can be designed with fewer interrupt pins.

Processor system with interrupt discrimination

Deflection apparatus for a raster scanned cathode ray tube display comprises a flyback circuit (T2,T4,Ly,Df,Cf) including a switch (T2,T4) connected in series with an inductor (Ly). The switch (T4) is responsive to a line drive signal (LINE) to alternately open and close a current path through the inductor (Ly) between a first voltage level (B+) and a second voltage level (0V) lower than the first voltage level (B+) to generate a raster scan current signal in a deflection coil of the display. The amplitude of the raster scan signal is determined as a function of the first voltage level (B+) and the frequency of the line drive signal (LINE). A feedback circuit (D2,R3,D3,C2) connected to the switch (T4) generates a feedback signal (F) as a function of current flowing out of the switch (T4). A regulator (600-630,T3,L,D1,C1) is connected to the flyback circuit (T2,T4,Ly,Df,Cf) for varying the first voltage level (B+) as a function of the feedback signal (F) to maintain a constant raster scan width despite variations in the frequency of the line drive signal (LINE).

Deflection apparatus for raster scanned CRT displays

A deflection apparatus for a raster scanned cathode ray tube display, the apparatus comprising: a ramp generator having a flyback circuit including a first inductor connected in series with a first transistor switch, the first transistor switch being responsive to a line drive signal to alternately open and close a current path through the first inductor between a first voltage level and a second voltage level lower than the first voltage level to generate a raster scan current signal in a deflection coil of the display, the amplitude of the raster scan current signal being determined as a function of the first voltage level and the frequency of the line drive switching signal, and a boost circuit connected to the flyback circuit, the boost circuit comprising a second inductor connected in series with a second transistor switch, the second transistor switch being responsive to a pulse signal synchronized to the line drive signal to alternately open and close a current path through the second inductor between the second voltage level and a third voltage level higher than the second voltage level to generate the first voltage level, the first voltage level being determined as a function of the third voltage level and the width of the pulses of the pulse signal; and a regulator connected to the flyback circuit and the boost circuit for varying the width of the pulses of the pulse signal as a function of the amplitude of the line scan signal to maintain a constant raster line width as the frequency of the line drive signal is varied.

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Hassocks, United Kingdom

David Leaver