The presence indicator systems that IM users must log into required more infrastructure.

IM 用户必须登录的状态指示器系统需要更多基础结构。

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For example, log utilization rate is an example of an upper bounded threshold indicator.

例如，日志利用率是一个设有上界的阈值指示器。

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As an indicator of how deeply Copious is betting on Facebook, people are required to use Facebook to log in and join Copious.

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