
PART VIII.         IDENTIFYING THE ESN IN YOUR CELLULAR PHONE

        Depending on what model phone you have, the ESN will be located on a
PROM.   The PROM is programmed at the factory, and installed usually with the
security fuse blown to prevent tampering.  The code on the PROM might 
possibly be obtained by unsoldering it from the cellular phone, putting it in
a PROM reader, and then obtaining a memory map of the chip.

        The PROM is going to have from sixteen to twenty-eight leads coming
from it.  It is a bipolar PROM.  SEE ESN.GIF FOR ADDITIONAL INFORMATION.
The majority of phones will accept the National Semiconductor 32x8 PROM,
which will hold the ESN and cannot be reprogrammed.  If the ESN is known
on the phone,  it is possible to trace the memory map by installing the PROM
into a reader, and obtaining the fuse map from the PROM by triggering the
"READ MASTER" switch of the PROM programmer.  In addition, most PROM 
programming systems include a verify and compare switch to allow you to 
compare the programming of one PROM with another.

        As said earlier, the ESN is uniformly black with sixteen to 
twenty-eight leads emanating from it's rectangular body, or square shaped
body.  If it is the dual-in-line package chip, (usually found in 
transportables and installed phones),it is rectangular.  If it is the plastic
leaded chip carrier (PLCC), it will be square and have a much smaller
appearance.  Functionally, they are the same chip, but the PLCC is used with
hand held cellular phones because of the need for reduced size circuitry. 
It will have a notch within, and also have writing in small white letters
on it. (A black chip with small white letters? Should be easy to spot huh?).
Look for the follow letters on the chip:

                                MMI
                                TI
                                NS
                                HARRIS
                                NSC
                                MB
                                DM
                                HM
                                AMD
                                TBP
                                MOTOROLA
                                AMPS


Once you have found the chip, try ordering a new one (maybe a couple of new
ones) from the businesses in the MERCHANDISE SECTION located at the end of
this file.

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