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States of telephone instruments dialer & receiver.

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States of transferring machines of first main exchange.

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States of transferring machines of second main exchange.

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State of radar.

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Negation of.

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Conjunction, disjunction respectively.

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Reliability of the ith component of considered system corresponding to system state.

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Reliability of the system as a whole.

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Reliability functions, in case, failures follow Weibull, exponential time distribution, respectively.