There are turn-key systems that anyone can start with little or no experience.

还有交钥匙系统，任何人都可以先从很少或没有经验。

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Integration with key systems and aggregation capabilities support user productivity.

集成关键系统和聚合功能，支持用户工作效率。

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Choose hotels that have electronic key systems where the rooms are re-keyed after guests check out.

选择有电子钥匙系统的旅馆，这种旅馆在客人结帐离开后，房间会重设密码。

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Some fire chiefs in California say that residents should always be encouraged to evacuate, but Naomi Brown, from the Australasian Fire and Emergency Service Authorities Council, says installing effective early warning systems is the key.

VOA: standard.2009.06.24

For instance, satellite operators can power-down key systems to prevent the possible damage to the systems.

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The development of practical public key systems also made possible other innovations.

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But for most encryption systems, especially the Public Key systems that are widely used by the banks, you need to know very sophisticated number theory, analytic number theory, elliptical theory.

NPR: The Math Behind Pellicano's Code