Communications: electrical – Visual indication – Switchboard or panel type
Patent
1998-02-20
1999-11-02
Lefkowitz, Edward
Communications: electrical
Visual indication
Switchboard or panel type
340458, 340641, 340642, 34081544, 34081547, 34081553, 359 59, 359 72, G08B 502
Patent
active
059778792
ABSTRACT:
A display device having driving circuits one for each of its light-emitting elements permits easy inspection of the driving circuits. The display device is formed as a fluorescent display tube that has an array of light-emitting units each consisting of a light-emitting element and its driving circuit. The display device further has a multiple-stage AND circuit consisting of 2-input AND circuits connected sequentially. One input of each stage is connected to the output of one of the driving circuits, another input of the first stage is connected to a power line, and the output of the last stage is connected to an inspection terminal, so that inspection is performed by checking whether a driving voltage appears at the inspection terminal. By activating all the driving circuits, whether they are functioning properly when they are in operation is checked globally; then, by deactivating one of the driving circuits, whether they are functioning properly when they are not in operation is checked individually. Instead of the multiple-stage AND circuit, a multiple-stage OR circuit may be used, in which case the other input of the first stage is grounded, and the output of the last stage is connected to the inspection terminal.
REFERENCES:
patent: 3792276 (1974-02-01), Toman et al.
patent: 4143297 (1979-03-01), Fischer
patent: 5056897 (1991-10-01), Akiyama et al.
patent: 5377031 (1994-12-01), Vu et al.
patent: 5402157 (1995-03-01), Nagato et al.
Lefkowitz Edward
Rohm & Co., Ltd.
Woods Davetta
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