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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. *****************************************************************************