The following describes how to get the real electronic serial number (ESN) from a Qualcomm QCP-1900.
Near as I can tell, the number on the sticker in the battery compartment is completely unrelated to the ESN and is used only to calculate the unlock code. To get the real ESN you will need to connect the phone to your computer. The GDIP cable I use for this has a DB25 serial interface and is part number CV90-22956-1. You will also need either the Qualcomm Phone Utilities or Qualcomm Phone Support Tools (QPST).
Qualcomm Phone Exchange, part of the Qualcomm Phone Utilities, allows you to backup your phonebook and other settings. The filename used to save this information contains the ESN of the phone in hex. Using an old dead phone as an example, the filename “QCP-1900 – 01981115.qpf” indicates the hex ESN of this phone is “01981115″. Inside this save file is also a field labeled “ESN=”. This field does not contain a valid ESN, but can be used to calculate the ESN. Although ESNs use a special hex to decimal conversion, Qualcomm Phone Exchange uses the normal hex to decimal conversion for this field. In order to calculate the ESN from this field, you must use the same incorrect conversion the Qualcomm software used, in reverse. For example, if the file contains “ESN=26743061″, simply put “26743061″ into your calculator in decimal mode, and then change to hex mode. For our example you will get “1981115″. QPST will likewise display the ESN as “1981115″. Note that in either case you will need to add the leading zero.
Any way you do it, once you have the correct hex ESN, you will then need to convert it to decimal using the conversion specific to ESNs. A quick Google search finds such a converter here. Entering “01981115″ into the hex side of the converter and hitting convert will give you a decimal esn of “00109965845″. This is the ESN your cellular company needs.
