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US2876286A
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Arrangement for the identification of special service apparatus required for connections in a telecommunication system
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US2664459A
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Automatic switching means for use in telegraph systems and the like
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US2753399A
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Circuit for controlling a selector
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US2648057A
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Circuit for obtaining electric bridge equilibrium
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US2611815A
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Signaling system
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US2577147A
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Arrangement for the identification of potential differences
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US2689300A
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Arrangement to obtain a voltage interval multiplier
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US2654837A
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Wheatstone bridge testing arrangement
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US2551694A
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Tube termination for telegraph purposes
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US2599344A
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Telegraph exchange for lines with simplex or duplex characteristics
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US2584153A
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Zero voltage identification device for selector positioning
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US2546369A
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Start-stop repeater
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US2556975A
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Bridge marking receiver
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US2602117A
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Line adapting telegraph repeater
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US2543050A
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Variable voltage selector
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US2636932A
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Relay counting chain using double-coil relays
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US2598822A
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Signaling system with private branch exchange subscriber
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US2608615A
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Automatic telegraph system controlled from the teleprinter keyboard
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US2652446A
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Release signal for telegraph systems
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US2574224A
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Circuit for marking a line as busy
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