Cell Phone Test Modes
By David Jones
Most cellular phones have what technicians call “field test mode”, which displays the signal strength more precisely, as negative numbers instead of bars; closer to zero means a stronger signal (zero means you’re standing on a cell tower).
Field Test Mode consists of several different screens on a cell phone that will display a variety of diagnostic information. Field Test Mode allows a user or a field technician to gain access to much more information than the simple “signal bar” indicator on the phone.
One can observe received signal strength (RSSI-Received Signal Strength Indicator). This is measured in dBm and is always shown as a negative number, even though some phones do not show the “-” character on the display. The higher number means better received signal and closeness to the tower. Example: -70 dBm is higher then -90 dBm.
One can observe the transmit power of the phone, this is usually displayed in dBm for CDMA phones. TDMA, GSM and iDen phones use a numerical figure that indicates the power level as it is cut back from the phone’s maximum power.
Another useful tool is the ability to monitor the channel number and operating frequency band. In some cases the uppercase letters from “A” to “F” represent the PCS band (1900 MHz), and lowercase letters “a” and “b” represent the cellular band (800 MHz). All other phones will show only the letter P or C to represent the 1900 or 800 MHz band respectively.
Here is a sample test mode for the iPhone:
Apple iPhone Test Mode
In phone mode dial *3001#12345#* then press CALL.
The Field Test Screen will appear. Select “Cell Information.”
Signal Strength is on the top line after RX-. Frequency follows FQ and is based on the channel number (i.e. 100-200 is 800 MHz and 500-700 is 1900MHz). The top line displays information about the tower you are using. The lines below display info about your neighboring towers.
Note: Signal strength, measured in decibels (dB), is expressed as a negative number. On certain phones, the number may show as positive in test mode. In such cases, convert it to negative. For example, 60 dB is actually -60 dB. The higher the number, the stronger the signal. Thus, -60 dB is a stronger signal than -75 dB. Contact Wilson Electronics Technical Support Department at 866-294-1660 if you have questions, or if you need assistance with the test mode of your cell phone.
Click here for Complete List of Cell Phone Test Modes.