iPhone iOS 4.1: See Numeric Signal Strength and How to Keep Field Mode Enabled Forever

   Posted September 8, 2010 by David Kirk in Apple iPhone

With the iOS 4.1 Apple has re-enabled field test mode. This allows the user to see the exact cellular signal stretch instead of bars. This tutorial also shows how to trick the iPhone into staying in this mode.

No shocker here. Apple has once again enabled the ability to see the numeric strength of your cellular signal. This is Apple’s way of showing that the majority of call issues are really AT&T’s poor network.

Forget the bar showing signal strength. Now you can actually compare numbers. To enable, dial the following code:


how to enable field test mode

Tap the signal strength to change from numbers to the graph. Press the home key to exit.

The scale is based on a logarithmic scale so don’t let the negative numbers fool you. Any greater than -100dBm is adequate while -50dBm, for example, is practically perfect coverage. More negative than -110dBm you have a high risk of call failure.

If you want to keep this mode active permanently, you can do the following trick:

1. Dial the code above
2. When the phone enters test mode, hold the OFF button until the screen says Slide to Power Off. Let go of the off button.
3. Hold down the HOME key and keeping holding it while you press cancel. Continue to hold the HOME key until you return to your regular screen.

Note this doesn’t work, some users have found that pressing the CANCEL key is not required. Thus, let go of the OFF button and then press the HOME key until the regular screen returns.

4. You should be able to use your phone normally while keeping Test Mode enabled.
5. If you want to switch back to the bars, just single tap on the numbers.


About David Kirk

David Kirk is one of the original founders of tech-recipes and is currently serving as editor-in-chief. Not only has he been crafting tutorials for over ten years, but in his other life he also enjoys taking care of critically ill patients as an ICU physician.
View more articles by David Kirk

The Conversation

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  • Chuck Gartland

    This appears to stop working once the Field Test screen is closed. Is this dependent on the version of the hardware maybe? I am still using my 3G.

    • http://www.tech-recipes.com David Kirk – Founder/Editor

      I haven’t had a chance to update our 3G devices yet. On my iPhone 4 devices, it definitely works as described.

      If you just type in the code, it will only work until you press the HOME button. If you want the numeric measurements to continue, you have to do the turn off-home button-cancel trick as described above.

      • Bart

        i didnt have any luck with keeping it there until i just held the home button from the power off screen without hitting cancel. ive got a 3gs

  • RMI

    I just downloaded 4.1 and when I Doubletap, nothing happens

    • http://www.tech-recipes.com David Kirk – Founder/Editor

      You downloaded 4.1, entered the code, and in test mode nothing happens?

  • Guest

    Ok, I managed to switch it on, but unable to switch it off:)
    it remains after complete restart of the iphone, no matter I call the number and exit with HOME button
    any idea?

    • http://www.tech-recipes.com David Kirk – Founder/Editor

      I have shown multiple people how to do it and haven’t seen a problem. Enter the code again… when you are in the test mode screen just press the HOME key.

    • http://www.tech-recipes.com David Kirk – Founder/Editor

      I’m changing my story. I’m unable to switch it off either. If you want bars, you can single tap to go back to bars… but if you click on the bars, you can always get the numbers again.

      • Golphur

        Did anyone find out how to disable this once you’ve permanently enabled it?

  • Jadenwalker

    I’m able to turn it on with my iPhone 4, but can’t get it to stick. I use the trick above, but once I exit Field Test, it turns back to bars. Any idea what’s up?

    • http://www.tech-recipes.com David Kirk – Founder/Editor

      Yeah, it’s an akward movement to get it to stick.

      Once in test mode press the OFF button until the slide appears. Press and hold the HOME key while pressing the cancel button. I need to do a video to show how to do it…

      • http://twitter.com/JeremyDurocher JD

        if you can post a video, that would be great. I have tried this about 10 times and cannot get the numbers to stay.


  • Sam Cowger

    This doesn’t work on my iPhone 3GS because when i hold down the home button and hit cancel, about 5 seconds later the voice control comes up. Help!

  • Question Asker

    Any way to do this on an iPod Touch to see Wi-Fi strength?

    • Anonymous

      Not that I am aware.

  • golphur

    So once you are in permanent mode you are stuck. You can click the numbers to go back to bars but once you open an app it defaults back to numbers….not good. Has anyone figured out how to disable the permanent mode yet? Reboot was no help.

    • Anonymous

      Nope. Permanent.

      I’ve tried hard reset, etc. It sticks.

    • Jeff355griffith

      I have the same problem too, to disable them you must restore as a new iPhone. But, you’ll lose texts, notes, and any important saved data. So use caution if you have anything important like me, I use time tracker for my job so if I do this I will lose all my hours and no paycheck!! I’ll do it after I finish this pay period.

      • Jeff355griffith

        I should have read on, yes you can disable it without any hassles! Just like the one guy said click on “Reset All Settings” you WON’T lose anything except wifi passwords and wallpaper but it will change back to bars!!

  • Lambwriter

    The info about hitting “Cancel” & holding down the home button is NOT accurate. Everything else about the process above is Correct. ONLY hold down the HOME button and wait for your home screen to appear and you have the best of both worlds. DO NOT click on “Cancel” & hold down the HOME button!!! This will only lead you to the VOICE CONTROL and more frustration.

    • Anonymous

      Thanks, Lambwriter. Information added to the original article.

  • Travmeister

    Worked for me on my 3GS. It didn’t work with the cancel button, I just held down the home screen button.

  • Guest

    Anyone know how to get out of permanent mode?!!

  • Jasarien

    How to disable the permanent field testmode:

    – Open Settings app
    – Go to General
    – Scroll to bottom
    – Go to Reset
    – Tap “Reset All Settings”

    This will restore the original ‘bars’ and remove the signal strength numbers. No data or media will be deleted, but you will have to reconfigure your WiFi and passcode, etc.

  • Blood

    Jail Break , download SBSettings and the use numeric GSM , its perfect and it will change to bars and numeric when you tap it.

    • Hiral Patel

      wow you’re great. i was always looking for this. thanks. 

  • http://www.forexabc.lt Forex

    I can not get it workin in Lithuania with 3G. Help!!!

  • Sam

    If you want to disable the permanent numeric display just reverse the process above, 1) launch field test display
    2) Touch the signal strength to toggle back to bars
    3) Do the home button trick
    Sorted your phone will now only show bars.

  • http://www.facebook.com/TimGray4 Timothy Gray

    Restore the phone and then restore from backup.  you always make a backup of your phone right?

  • Pingback: Voice Navigation - iPhone, iPad, iPod Forums at TiPb.com()

  • Swayne28

    You don’t need to reset anything to disable it just enter the field test again make sure it’s showing bars then back out with the home button job done

  • Jeffry

    If you want to remove the number permenantly , you just have to open the sbsetting , choose more, system option and swith off numeric GSM .. Hope this work ..the number keep showing , it is very annoying -,-

  • Amanda

    Thanks, that’s awesome! The second way was the only way I could get the field test to be permanently displayed. This was the way without pressing cancel. Thabks!