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Fail-safe time delay circuit
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Patent number 4,059,845
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Issue date Nov 22, 1977
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Westinghouse Air Brake Company
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Dick J. Kolkman
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H01 - BASIC ELECTRIC ELEMENTS
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Shunt enhancement logic circuit
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Patent number 3,958,782
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Issue date May 25, 1976
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General Signal Corporation
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Henry C. Sibley
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H03 - BASIC ELECTRONIC CIRCUITRY
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3842746
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Patent number 3,842,746
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Issue date Oct 22, 1974
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B61 - RAILWAYS
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3815866
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Patent number 3,815,866
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Issue date Jun 11, 1974
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B61 - RAILWAYS
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3710100
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Patent number 3,710,100
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Issue date Jan 9, 1973
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B61 - RAILWAYS
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3691368
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Patent number 3,691,368
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Issue date Sep 12, 1972
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B61 - RAILWAYS
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2806943
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Patent number 2,806,943
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Issue date Sep 17, 1957
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B61 - RAILWAYS
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2620435
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Patent number 2,620,435
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Issue date Dec 2, 1952
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B61 - RAILWAYS
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2540089
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Patent number 2,540,089
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Issue date Feb 6, 1951
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G08 - SIGNALLING
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2457663
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Patent number 2,457,663
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Issue date Dec 28, 1948
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B61 - RAILWAYS
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2454249
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Patent number 2,454,249
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Issue date Nov 16, 1948
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B61 - RAILWAYS
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2380864
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Patent number 2,380,864
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Issue date Jul 31, 1945
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B61 - RAILWAYS
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2255797
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Patent number 2,255,797
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Issue date Sep 16, 1941
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B61 - RAILWAYS
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2244797
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Patent number 2,244,797
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Issue date Jun 10, 1941
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B61 - RAILWAYS
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1924603
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Patent number 1,924,603
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Issue date Aug 29, 1933
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B61 - RAILWAYS