January 9th, 2010, 05:17 PM
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Sleep mode starts the moment the screen goes dark - so long as you are not running an application which prevents sleeping. (The screen can be blanked, but applications can still prevent it from fully "sleeping", for instance listening to music.)
Convince yourself of it this way:
- Exit any apps you are using (with a task manager, or whatever) so the phone is in a "quiet" state.
Edit: Put Settings in your ATK exclusion list.
- Settings -> About phone -> Status and scroll all the way down
Locate the "Awake time" at the bottom of the screen and note that it is increasing.
When it rolls over to a full minute, hit the End button precisely at that moment, so that the screen sleeps - and remember the number of whole minutes the counter was at.
- Now wait 2 or 3 minutes.
- Wake the phone up and quickly unlock the screen - and quickly look at the "Active time" status.
If there was no activity, you'll notice that the active time is only a few seconds more than the elapsed active time when you blanked the screen - about the amount of time it took you to unlock the screen, and maybe a few seconds more than that.
Note there is nothing special about "sleep mode" that prevents applications from running. After all, it's the way the phone is designed - for instance be able to receive "push e-mail", or periodically retrieve "pull e-mail" while the phone is sleeping. Obviously, though, the goal is to try and save power, so the OS schedules processes for execution less frequently depending on their status (ForeG, BackG, etc), delivers interrupts less urgently, etc.
Also, applications can choose to receive notifications about power state - and change their behavior as a result of that, so the fact that you sometimes hear a noise 10-20 seconds after you have powered off the screen might just be an app responding to that state change.
If you do the same thing overnight (monitor the increase in active time), you'll see that the phone accumulates some number of minutes of active time. How much additional time it accrues depends on not only the apps you have installed/running, but also how much mail you are receiving, your app settings, etc.
Last edited by erisuser1; January 9th, 2010 at 05:28 PM.