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What is field test mode and how to activate it

April 6, 2017 — by KEN PERKINS

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How to access iPhone field test mode

 

 

It’s often useful to know how strong a signal your iPhone is receiving. If you’re trying to make a call but it won’t go through or if you’re otherwise not getting the cell service you expect, then knowing your signal strength can help you determine why not.

Of course virtually all phones have the “bars” or “dots” graphic that displays on your home screen, supposedly so you know what your cell phone signal strength is.

The problem with relying on those graphical representations for an indication of signal strength is that they are not backed by any standard. That means the accuracy of the dots or bars can vary widely.

Viewing your iPhone’s actual signal strength reading is always preferable to relying on the dots graphic. Signal strength is measured in dBm, or decibel milliwatts, a standard unit of measure.

By viewing the dBm reading on your iPhone you know with certainty how strong a signal you are receiving, and whether the signal needs boosting. To see the dBm you must enter a sequence of commands to put your iPhone into ‘Field Test’ mode and display the reading.

 

How to put your iPhone into Field Test Mode

The following instructions work for iPhone 5 and higher models running iOS 9 or later.

First, you must turn off LTE. To do this, go into Settings, then Cellular, then Cellular Data Options. Make sure the Enable LTE status is Off. You can turn LTE on again after viewing the dBm reading. Now to put your iPhone in Field Test Mode:

  • Dial *3001#12345#*
  • Press CALL
  • Hold the power button for about 5-7 seconds until you see the “slide to power off” screen.
  • Do NOT power off the phone!
  • Hold the home button for about 5-7 seconds.
  • It will return you to the home screen and you’ll see the dBm reading at the top of your screen.

 

Some helpful tips

dBm is typically expressed as a negative number, -88 for example. The closer to zero the reading is, the stronger the cell phone signal. So for example, -79 dBm is a stronger signal than -88 dBm.

A reading of -50 is about the strongest signal you will see. When a signal is weaker than -100 dBm, that’s a pretty weak signal. If the signal gets much weaker than that, you likely won’t have service.

If you don’t want the dBm reading to display on your iPhone home screen, you can dial the number sequence again and just hit “back to phone” and it’ll return to the dots graphic.

If you need to take dBm readings in several locations – to determine where the strongest cell signal is found, for example – you can put your iPhone into Airplane Mode for a few seconds after taking each reading. Doing this will reset your phone after each reading so the next dBm reading will be accurate.

To access Airplane Mode, swipe the screen from bottom to top. Then tap the airplane icon to turn on Airplane Mode. Wait 5-10 seconds, and then tap the icon again to turn it off.

 

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How to access iPhone field test mode

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TAGS: signal booster for iphone, Signal Strength, understanding cell phone facts

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