Tip: check your cell signal with the Received Signal Strength Indicator

By , Jul 21, 2016

AT&T Field Test Status Bar RSSI iPhone

When you have an iPhone, your carrier’s signal strength can be one of the most important things that helps you decide which carrier to go with. In this tutorial, we’ll show you how to enter Field Test mode on your iPhone and display the RSSI value in the Status Bar, rather than the basic signal bar indicators.

Showing the RSSI value in your iPhone’s Status Bar

You’re probably used to seeing the five little dots just to the left of your carrier’s name in your Status Bar, and this is an indicator that’s meant to make sense to just about everyone.

On the other hand, if you have any knowledge of wireless signals at all, then you probably know there’s this thing called the Received Signal Strength Indicator (RSSI), which displays the signal strength as a number instead of as a set of dots.

It’s possible, without a jailbroken device, to show the RSSI in your Status Bar rather than the signal strength dots, and although it’s temporary, it can be useful in discovering dead zones and learning what carrier is the best for your everyday needs.

I do want to point out that in 2010, Sebastien touched on how to do this in iOS 4.1, but iOS 9 and later introduced this thing called Breadcrumb links in the Status Bar, and because of this, when you attempt to show the RSSI in the Status Bar, you will see “Back to Phone” instead.

So there are a few extra steps on iOS 9 and later, and in this tutorial we’ll show you how to cheat the system and show the RSSI in your device’s Status Bar just the same as you could in earlier versions of iOS.

How to do it

To show the RSSI in your Status Bar, follow these steps:

1) Begin by launching the Phone app on your iPhone, and then dial *3001#12345#* and tap the Call button.

Phone App Enter Field Test Phone Number

2) Rather than imitating a call, this will open the hidden Field Test app on your iPhone.

Field Test App iPhone

3) Next, press and hold the power button until you see the slide to power off slider.

Slide to Power Off iPhone

4) Now, press and hold the Home button until the app closes and you’re back on your Home screen.

Field Test Home Screen

Take note that the Status Bar now displays the signal strength as RSSI instead of signal bars.

AT&T Field Test Status Bar RSSI iPhone

That’s all there is to it!

To show the basic signal bars again, just tap on the signal strength in the Status Bar. You can also tap it again to show the RSSI signal once again more easily, which is great if you want to compare the two for accuracy.

Understanding RSSI

Because not everyone is familiar with RSSI, it’s important to know what these figures mean. In radio signal troubleshooting, the numbers are always negative, so you always want to take the absolute value of the number you see. Once you do, keep in mind that a larger integer is worse and a smaller integer is better. So -115 is a rather poor signal, while -55 is a much preferred signal.

If you’re consistently getting anything higher than maybe about -80, you probably aren’t getting very good service. Obviously, you should notice your signal is horrendous even if you are just monitoring the signal bars, but the RSSI gives you a slightly more intuitive way to see real-time signal strength changes in a fine-grained way.

Wrapping up

Field Mode probably isn’t something you’re going to use all that often, but it’s good to know. This mode has been around on iPhones for a very long time, and the only reason we’re showing you how to do this again is because iOS 9’s Breadcrumbs links made things a little screwy.

Did you know Field Mode existed, and do you prefer to see the RSSI? Share in the comments!

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  • I came up with this in 2007

    • Chris
    • Bill

      You didn’t really ‘come up with’ it. Perhaps you mean you found out how to access it in 2007.

      • Yes you’re right I actually found out how to set this on your desktop and not just the field test app. I posted the original find in 2007 on Apple forums on a thread that reached 30,000 something post

  • Brian Cheetham

    “a larger integer is worse and a smaller integer is better. So -115 is a rather poor signal, while -55 is a much preferred signal.” I hate to bring math into this but -55 is larger than -115. smh

    • Chris

      Signal strength for cell phone/Wi-Fi bands work from negative zero and up, the reason for this is to show you how strong of a signal you’re receiving from the baseline.

      The closer you get to negative zero, the stronger the signal will be and the less interference you will have.

      E.g. -115 means your dBm is 115 milliwatts weaker to the source signal than the tested 100% strength the radio can send/receive at.

    • Are you familiar with absolute value? Cell signals work very differently than you’re used to with a number line.

    • Shinonuke

      Hate to bring math into this but you missed the line about absolute value:

      “In radio signal troubleshooting, the numbers are always negative, so you always want to take the absolute value of the number you see.”

      So absolute value of -115 is 115 or |-115| = 115. Now compare -55 and -115 after the absolute value: 55 vs 115. 55 is smaller than 115.

      Again I hate bringing math into this.

  • Innes

    tapping the status bar doesn’t put back the original dots for me

    • Bill

      You have to tap the numbers, and it can be tricky to hit them in just the right spot. But once you figure out where that spot is you should be able to toggle between dots and numbers.

  • Gabriel Anaya

    The number view won’t go away from the status bar no matter how many times I dismiss it. I have to dismiss it with each app I go into and rebooting doesn’t stop it either. Some apps I can’t even dismiss it because of its closeness to menu options, like in messages.

  • Marcelo Bernardes

    How to revert? if I don’t want RSSI anymore, even when I tap the bars…
    Anybody knows???

    • MrTarek

      Me too , so bad when they put a tutorial on something and they don’t have a way back

    • Bonda Gangadhar

      To reverse course and get rid of the signal strength numbers, go back into Field Test mode as you did in step 1 above and then simply hit the Home button to exit Field Test mode

      • Marcelo Bernardes

        Thanks Bonda! It worked just fine =)

  • J™

    I think the article should also show how to get rid of the RSSI

    1) open the phone app and dial *3001#12345#*
    2) Press the home button

    RSSI is gone.

    • MrTarek

      Doesn’t work for me

      • Innes

        Just press the home once. Dont press and hold.

  • MrTarek

    I can’t get back to the dots , help plz