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Coin-telephone auditor
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Patent number 4,599,492
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Issue date Jul 8, 1986
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David Otten
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Automatic switching matrix
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Patent number 4,326,191
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Issue date Apr 20, 1982
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Massachusetts Institute of Technology
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Martin F. Schlecht
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H01 - BASIC ELECTRIC ELEMENTS
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Totalizer system
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Patent number 4,201,907
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Issue date May 6, 1980
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International Totalizing Systems, Inc.
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David M. Otten
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G07 - CHECKING-DEVICES
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Totalizer for vending machine
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Patent number 4,143,749
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Issue date Mar 13, 1979
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International Totalizing System
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David M. Otten
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G07 - CHECKING-DEVICES