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US4581694A
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Inverter using parallel connected series pre-regulator and a synchronized switch
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CA1209292A
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Subscriber's telephone circuit
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CA1209291A
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Subscriber's telephone circuit
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High gain cascode amplifier with negative feedback
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Master unlock circuit for an electronic telephone
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Transient resistant key operated pulse generating calling device circuit
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Protection circuitry for subscriber's telephone circuit equipped with repertory memory
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Secretarial telephone station for use with a secretarial answering system
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Secretarial answering system
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Subscribers telephone hold circuit with automatic disconnect
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Current regulated pulse dialer with memory retention circuit
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Amplifier for use with telephone transmitter mounted in hand held telephone unit
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Dual timing circuit for telephone subscriber's instrument
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Network control center call trace
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Internodal conference call administrator
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Telecommunication trunk circuit reporter and advisor
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Power supply control apparatus
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