The connections at each end create a channel reserved for the duration of a call.

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And even if investigators intercept a Skype call by tapping a suspect's internet connection, its strong encryption means they are likely to be able to determine only the time and the duration of the call.

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Generous loan covenants give managers more flexibility to work through their debt, and lenders are keen to extend the duration of loans rather than call them in and face more write-downs.

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Participants underestimated the number of calls they had made by an average of about 20%, and overestimated call duration by 40%.

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But Krewski said that overall people generally have a good ability to recall the number of phone calls reasonably accurately, and tend to overestimate call duration by about 40 percent.

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That means that when a call begins, the network essentially opens a path of communication for the duration of the session between the users.

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