Calculator theft prevention device

Details Calculator theft prevention device Calculator theft prevention device

1976-04-27

1978-07-25

Pitts, Harold I.

Communications: electrical

Digital comparator systems

340149A, 340365E, 340571, G08B 1306, H04Q 100

Patent

active

041032896

ABSTRACT:
A security device for an electronic calculator consists of an electronic circuit within the calculator which permits operation of the calculator only after the operator has correctly operated a predetermined sequence of keys. The circuit is connected to the sense and the digit drive lines of an electronic calculator having an electronically scanned keyboard. The circuit includes a key selection matrix, a valid actuation discriminator logic, an actuation sequence counter, an alarm inhibiter and an alarm which disables the proper functioning of the calculator.

REFERENCES:
patent: 3633167 (1972-01-01), Hedin
patent: 3781804 (1973-12-01), Lederer
patent: 3839710 (1974-10-01), Rogers
patent: 3940738 (1976-02-01), Teeters

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