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Ring line concentrator
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Patent number 5,101,405
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Issue date Mar 31, 1992
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Hitachi, Ltd.
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Yoshinori Bekki
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Ring network configuration
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Patent number 4,937,823
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Issue date Jun 26, 1990
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Hitachi, Ltd.
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Yoshinori Bekki
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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Loop transmission system
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Patent number 4,435,704
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Issue date Mar 6, 1984
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Hitachi, Ltd.
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Toyokazu Hashimoto
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H04 - ELECTRIC COMMUNICATION TECHNIQUE