Apple iPhone iOS Field Test USSD Codes & RSRP Signal Decibels Directory
Access hidden iPhone dialer interrogation codes, launch iOS Field Test Mode (`*3001#12345#*`), decipher 5G/LTE RSRP signal decibels (-dBm), and verify carrier call forwarding, IMEI, and EID numbers.Documentation & FAQs ↓
iPhone Field Test RSRP Signal Quality Meter
Enter or slide your current Reference Signal Received Power (dBm) obtained from Field Test mode.
Reliable connection for 4K streaming, FaceTime HD, and VoLTE calls. Typical urban indoor or suburban coverage.
iOS Engineering Field Test Mode
Opens Apple's low-level modem diagnostics console showing live cell tower serving ID, RSRP dBm, RSRQ, band frequency, and CA bandwidth.
Dial in the Phone app. On iOS 16/17/18, navigate to 'Serving Cell Info' or 'RAT - Radio Access Technology'.
Device IMEI, IMEI2 & EID Barcode Screen
Instantly displays your iPhone's 15-digit International Mobile Station Equipment Identity, digital dual-SIM IMEI2, and embedded eSIM EID barcode.
Triggers on input completion without needing to press the green Call button.
Check Unconditional Call Forwarding
Queries carrier switch for unconditional forwarding on Voice, Data, Fax, SMS, and Packet access.
Dial to audit whether incoming calls are secretly redirected to an unauthorized voicemail or foreign number.
Forwarding When Unanswered
Shows carrier forwarding number and ring timeout delay (typically 20-30 seconds) before sending calls to voicemail.
Inspects conditional call diversion when you decline or do not pick up.
Forwarding When Unreachable / Out of Range
Displays carrier routing when your iPhone is powered off, in Airplane mode, or out of cellular coverage.
Standard voicemail carrier routing check.
Forwarding When Line is Busy
Queries destination number when you are actively on another call with Call Waiting ignored.
Checks busy-line conditional forwarding status.
Check Call Waiting Activation
Audits whether second incoming calls beep during active phone conversations.
Displays current status for Voice and Data circuits.
Activate Call Waiting
Sends GSM network request to enable incoming second call notifications.
Enables Call Waiting across your cellular provider line.
Deactivate Call Waiting
Disables incoming second call notifications so callers get a direct busy signal.
Turns off Call Waiting on carrier profile.
Outgoing Caller ID Blocking Status
Queries whether your phone number is permanently masked as 'Private / No Caller ID' for outgoing calls.
Audits Calling Line Identification Restriction (CLIR).
Prefix Caller ID Block per Single Call
Prepend this code before any phone number (e.g. #31#1234567890) to suppress your phone number for that specific call.
Single-call caller ID mask.
Query Outgoing Call Barring
Inspects carrier locks that restrict international, roaming, or premium outbound calls.
Checks outbound call barring restrictions.
View SMS Center (SMSC) Routing Number
Displays your carrier's Short Message Service Center gateway address responsible for SMS routing.
Used to diagnose outgoing text message delivery failures.
Step-by-Step Instructions
4 Steps to CompletionOpen the native Phone app on your iPhone and tap the Keypad tab.
Dial *3001#12345#* and press the green Call button to launch Apple Field Test Mode.
Tap 'RAT Serving Cell Info' or 'Serving Cell Measurements' to locate rsrp (signal strength in -dBm).
Refer to our decibel rating scale: -50 to -80 dBm is Excellent, -81 to -95 dBm is Good, and below -110 dBm is Poor.
Practical Use Cases & Real-World Scenarios
Field Test Mode Guide (*3001#12345#*)
Step-by-step instructions to open Apple's hidden diagnostic menu and navigate 5G NR and LTE cell measurement dashboards.
True RSRP Decibel Signal Meter
Translates vague 1-to-4 signal reception bars into scientific Reference Signal Received Power decibels (-dBm).
Carrier USSD Interrogation Codes
Dial codes for Call Forwarding (*#21#), Call Waiting (*#43#), SMS Center Number (*#5005*7672#), and IMEI (*#06#).
eSIM & EID Number Inspector
Direct dial codes to display embedded SIM (eSIM) 32-digit EID and IMEI SV strings without digging through iOS Settings.
Frequently Asked Questions
What is Apple Field Test Mode and how do I open it?↓
What is RSRP and what do the decibel numbers mean?↓
Why did Apple remove decibel numbers from the iPhone status bar?↓
What is the difference between RSRP and RSRQ?↓
Do USSD secret dialer codes work on all cellular carriers?↓
15 Best Hidden iPhone Secret Codes To Use in 2026
Dive deeper into the foundational technical concepts behind this tool on our editorial blog. Includes comprehensive hardware benchmarks, case studies, and best practices.
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