"USSD Code”

"USSD Codes" (Unstructured Supplementary Service Data), commonly referred to as "iPhone Codes," is actually a standard set of GSM / UMTS / LTE commands that allows users to check the status, settings, or on / off functions of the SIM card and network directly from the phone screen.

Here is a detailed description of the key codes shown in the image, divided by categories of use for ease of understanding:

1. Body and network information category

*# 06# (IMEI Number Check): Once pressed, the screen will immediately display the IMEI ID code (IMEI), which is very important for using time to confirm a missing machine or notify the service center.

* 3001# 12345# * (Field Test Mode): It is an advanced test mode for technicians or users who want to see in-depth details such as numerical true signal strength (dBm), connected frequency band, and ambient signal mast data.

*# 07# (Legal and Regulatory Information): Shows the standard certificate, safety and radio wave energy absorption rate (SAR) of the unit.

2. Call Forwarding category

This group code is used to check or manage when someone calls us and we don't pick up. Where the call will be transferred (e.g. to a voicemail dispenser or another number).

*# 21#: Check all line transfers (incoming calls, data, SMS) if they are open

*# 61#: Check the wire transfer if we do not answer the call (and check the duration for seconds before the system transfers)

* # 62 #: Check for wire transfer in case of incommunicability (power off or no signal)

* # 67 #: Check the transfer if the line is busy (other calls are being discussed)

# # 002 #: Cancel and shut down the entire line transfer system. Immediately (It's a very good code to clear the default if it's afraid the line will be secretly transferred to another number)

3. Caller ID & Call Barring

* # 31 #: Check if we currently set "Hide Your Number"

# 31 # (followed by a call number): Hide the call number only on that line (the destination will not see our number, it will be known as Unknown or Private Number)

* # 33 #: Check Call Barring, such as blocking international calls.

4. Call Waiting category

It allows us to switch calls when people are stacking calls while they are stuck.

* # 43 #: Check if the call waiting system is active

* 43 #: Enable the call waiting system

# 43 #: Turn off the call waiting system

5. Check balance and service charge category (depends on network)

Caution: The code in this category in the picture is a foreign standard. For Thailand, it may vary by mobile camp (AIS, True, dta).

* 225 #: Check outstanding bill balance (for monthly system)

* 777 #: Check balance and usage date (for prepaid system)

* 646 #: Check the number of minutes you can call.

6. Message and Voice System (SMS & Voice) category

* # 5005 * 7672 #: Check the SMS Center Number. If this code is erroneous, we will not be able to send out the SMS.

* 3370 #: EFR Mode (Enhanced Full Rate) is an ancient code in the GSM system. It improves the sound quality of calls, but it can be exchanged with more battery waste. (In the current 4G / 5G era with VoLTE, the system automatically adjusts the sound, so this code has almost no effect). 💡 Introduction: > Most of these codes are international standards, but the actual results depend on your Operator. Some networks in Thailand may not support some codes, or they may switch to their own specific codes (such as checking money). Thai is usually * 121 # or * 900 #.) Pressing these codes is harmless to the machine, but may change some settings of the SIM card, such as inadvertently transferring or suspending the line.