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公开(公告)号：GB2287813B
公开(公告)日：1997-12-03
申请号：GB9405136
申请日：1994-03-16
Applicant: IBM
Inventor： BEETESON JOHN STUART , JACKSON FREDERICK SAMUEL
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公开(公告)号：GB2287813A
公开(公告)日：1995-09-27
申请号：GB9405136
申请日：1994-03-16
Applicant: IBM
Inventor： BEETESON JOHN STUART , JACKSON FREDERICK SAMUEL
Abstract: A display device comprises a display screen. A drive circuit (200) generates an image on the display screen (210) in response to an input video signal (R, G, B). Stand-by means (SL) disables the drive circuit (200) in response to a stand-by signal. Reset means (RL) restores operation of the drive circuit (200) on receipt of a predetermined security code from push-buttons on a user control panel (260). The invention prevents unauthorised access to data when the user of a computer system forgets to log-off after the display automatically enters stand-by mode.
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公开(公告)号：GB2279188A
公开(公告)日：1994-12-21
申请号：GB9312273
申请日：1993-06-15
Applicant: IBM
Inventor： JACKSON FREDERICK SAMUEL , LEAVER DAVID
IPC: H03K17/0812 , H04N3/16 , H04N3/27 , H02H7/20 , H03K4/08
Abstract: A CRT display scan circuit 100 having a switch transistor 101 with multiple frequency operation, has a supply voltage Vs which changes with changing scan frequency. A decrease in scan frequency at a rate faster than the supply voltage can decrease may cause overcurrent failure of the switching element 101. In a protection circuit, Fig. 2, a sawtooth voltage waveform representing the current flowing in the switching device 101 is synthesized at 208 based on the supply voltage Vs and the conduction time of the switching element 101, using a storage capacitor 339, current sink 200 and zero crossing detector 210. If the sawtooth voltage exceeds a reference voltage 214, a comparator 220 indicates overcurrent in the transistor 101 and terminates drive signal 108 in the current cycle or until the supply voltage has decreased.
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