4. Railway switches and signals
  5. Block-signal systems
  6. Automatic

John W. Caldwell, Jr.

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Battery monitor circuit

Communications: electrical – Condition responsive indicating system – Specific condition
Patent

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Electromagnetically responsive device and system for detecting t

Communications: electrical – Digital comparator systems
Patent

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Fail-safe voltage-limiting circuit for an audio frequency overla

Railway switches and signals – Block-signal systems – Automatic
Patent

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Keyboard for miniature data processing devices

Communications: electrical – Audible indication – Percussion-type sound producer
Patent

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Retractable roof top sign for automotive vehicles

Communications: electrical – Digital comparator systems
Patent

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Profile ID: LFUS-PAI-P-222190

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