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Practical Computer Advice
from Martin Kadansky
Volume 15 Issue 4
April 2021
Proximity Sensor: Useful New Security Feature or Major Remote-Help Inconvenience?

The problem
Has this ever happened to you? You’re using your computer normally when suddenly you find yourself on the “lock screen” (also known as the sign-in or login screen), where you have to select your computer username and enter your password (if you have one) to get back into your computer.
This might happen randomly, or repeatedly as often as every minute.
In particular, this might happen when you’re getting help from a computer person remotely, or trying to use your own computer over a remote connection.
The normal reasons that you would see the lock screen
Depending on your settings, most often you would only see the lock screen when:
  • You’ve just powered on your computer.
  • You’ve just done a manual Restart.
  • You’ve manually chosen the Sleep or Hibernate function, and then you later woke it up by moving the mouse or pressing a key on the keyboard.
  • You’ve chosen to go to the lock screen manually, typically using a keyboard shortcut or choosing “Lock” from a menu.
  • You’ve stopped using your computer for a while. After a period of “idle” time (when you didn’t touch the mouse or keyboard) the screen saver started, or it entered Sleep or Hibernate mode. Then you later woke it up by moving the mouse or pressing a key.
However, when this particular problem is happening, none of the normal reasons for landing in the lock screen apply.
It happened to me
Recently I was working remotely to set up a client’s new computer.
After he helped me establish the remote connection, I began to download and install the various programs that he would need, and I was adjusting a number of settings for him as well. I had been making good progress when without any warning his computer suddenly went to the lock screen. I had been actively using his new computer (moving and clicking the mouse, typing, etc.) so it wasn’t “idle,” and I hadn’t done anything that would have triggered the lock screen.
Thinking that it was just an odd fluke, I clicked his username, entered his computer password, and then continued where I left off. About a minute or two later I was suddenly back on the lock screen again. This cycle repeated over and over again, then it stopped happening for 5 or 10 minutes, then it started again. I tried a variety of things, none of which seemed to make a lasting difference.
The explanation
Worried that there was something wrong with this brand-new computer, we finally called the computer’s manufacturer. After I described the problem, the technical support person explained that this crazy behavior is actually a relatively new feature called the “proximity sensor.” It has two parts:
  • Hardware: Like most modern laptops, my client’s new computer has a built-in webcam. Built into the regular camera in this particular laptop (a Dell Latitude) is an infrared (IR) camera that can detect whether a person (technically, a thermal or heat source) is in front of the computer.
  • Software: However, the hardware wasn’t the entire explanation. Somehow the “proximity sensor” software got activated. This setting is specifically designed to monitor the IR camera and, as soon as it no longer detects anyone in front of the computer, it waits one minute and then locks the computer. This overrides all other power settings, including the ones that wait for an “idle” period of time.
This completely explained the partial randomness in this computer’s lock screen behavior! As long as my client was in front of the computer (or perhaps even just in the room), the computer acted normally. However, as soon as he left the room, the computer went to the lock screen one minute later, regardless of whether I was actively using the computer remotely.
In the case of this Dell laptop, we also learned the (not so obvious) solution: Open the Dell Optimizer software, click Proximity Sensor, and then disable it. Once we did that, the problem was solved!
Proximity detector pros and cons
As long as you have consciously chosen it (and you remember how it works), this can be a useful security or privacy feature, intended to protect the information in your computer from unauthorized people in the room (or walking by) who might access your computer after you’ve stepped away. On the other hand, as I found, this feature can make a remote-help session difficult and unproductive.
I can also imagine how it might go wrong. For example:
  • It might get activated if you cover your webcam with a piece of tape or a sliding cover, which could prevent the IR camera from detecting any heat sources.
  • It might be prevented from activating because you’ve got a source of heat in front of the computer that not only isn’t you, but also may be randomly active, like a radiator or space heater or a sometimes-sunny window or a pet.
So far I have also learned that this feature is currently built into many Dell Latitude and Dell Precision laptops. Other Dell models may include it in the future, and other manufacturers’ computers may also have something similar.
More on proximity detectors
This is just one example of what’s more generally referred to as a “dynamic lock,” whose purpose is to detect when you walk away and then lock your computer shortly after that.
While your screen saver, sleep, or hibernate settings can already do that after a predetermined amount of “idle” time (inferring that you’ve probably walked away based on your not having touched your mouse or keyboard for a while), a “dynamic lock” is a more proactive approach designed to detect that much more quickly.
One type of proximity detector is a computer accessory that you can buy which combines a few different technologies:
  • It plugs into a USB port on your computer.
  • You pair it with your smartphone via Bluetooth.
  • You adjust a few settings.
  • Then, since you’re likely to take your cell phone with you when you step away, when it detects that your phone has moved out of Bluetooth range (about 30 feet), it locks your computer.
You may already be familiar with other types of proximity sensors. For example:
  • When you’re on a call, your iPhone or Android smartphone screen may turn black when you raise the phone to talk, in order to avoid having your face trigger any of the on-screen buttons.
  • You may have the ability to set up facial recognition so you can unlock it without having to enter your passcode.
Where to go from here
  • google: proximity sensor
  • google: proximity detector
  • google: lock too quickly
  • google: lock screen one minute
  • google (case sensitive): usb proximity sensor OR detector
  • google (case sensitive): bluetooth proximity sensor OR detector
  • google (case sensitive, specific to Macintosh): usb proximity sensor OR detector mac OR macintosh
  • google: infrared camera
How to contact me:
phone: (617) 484-6657

On a regular basis I write about real issues faced by typical computer users. To subscribe to this newsletter, please send an email to martin@kadansky.com and I'll add you to the list, or visit http://www.kadansky.com/newsletter

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I love helping people learn how to use their computers better! Like a "computer driving instructor," I work 1-on-1 with small business owners and individuals to help them find a more productive and successful relationship with their computers and other high-tech gadgets.

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