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US3324249A
(en)
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Series pathfinding and setting via same conductor in tandem crosspoint switching netwrk
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US3676603A
(en)
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Code call circuit for paging in a pbx
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US3838223A
(en)
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Ring trip and dial pulse detection circuit
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US3729594A
(en)
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Line and link sensing technique for pabx telephone system
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US2438496A
(en)
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Telephone system employing key type call transmitter
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GB550235A
(en)
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Improvements in telephone systems
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US2377453A
(en)
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Telephone system
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US3497631A
(en)
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Add-on conference trunk
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US2660619A
(en)
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Level-hunting selector
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US3337692A
(en)
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Line lockout in a cross point switching system
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US3521001A
(en)
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Malicious call holding and tracing circuit
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US2857471A
(en)
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Selector switch circuit
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US3519752A
(en)
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Crosspoint selector for reed relay matrix
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US3772476A
(en)
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Digit impulse scanning arrangement for a communication switching system
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US2791635A
(en)
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P. a. b. x selector-connector switch
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GB496138A
(en)
|
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Improvements in or relating to telephone systems
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US3014989A
(en)
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Incoming telephone call pabx restrictive service
|
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US3832500A
(en)
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Automatic telephone system with improved line selecting apparatus
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US2525417A
(en)
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Selector switch metering circuit
|
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US3085133A
(en)
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Connector with automatically controlled ringing
|
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US3024316A
(en)
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Calling line and station identification system
|
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US3699263A
(en)
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Line scanner and marker arrangement using group scanning
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US3485955A
(en)
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Stuck relay alarm circuit
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US3441675A
(en)
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Dial pulse detecting system
|
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US1600444A
(en)
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Telephone-exchange system
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