Section 6 - Reading the SID

READING THE SID by Doctor Who (drwho@l0pht.com)

The SID (System IDentification) of a control channel can be determined using the test mode of the Motorola cellular phone. This document assumes the reader understands cellular technology in general, and how to access Motorola's test mode in specific.

Tune the phone to the desired control channel with 11xxxx# where xxxx is the channel number. Hit 39# to receive one control channel word. One should appear in less than two seconds, filling up all ten digits on the display with hexadecimal digits. Do this repeatedly until one is found with the correct pattern. Digit places start at the left hand side and go to the right.

The first digit should be C,D,E, or F. This letter can be used to determine the DCC/SAT of the cell. A "C" is SAT 0, D is 1, E is 2, and F is 3. Ignore digits 8,9, and 10. They are parity bytes. Digit 7 should be "6" or "E", though I have never found it to be other than "E". The hexadecimal value of represented by digits 2 through 5 is then divided by two, and then 1 added if the carrier as an "A" side, "non-wireline" carrier. The result is the system ID.

for example:

E00388EA08

E means this cell has an SAT/DCC of 3. The A08 is ignored. The E to the left of it is proper and normal, so this is the right kind of message. Ignore the 8 in position 6, that is just to the left E. 0038 in hexadecimal translates ((3*16=48)+8) to 56. 56/2=28. Looking up System ID 28 on my chart indicates Nynex in Boston. This is correct.

Please be aware that the two SID charts I have seen around the net are very outdated. I have a more recent version on paper which I may eventually type in, when I have the time and energy.

The methods used above are only a very crude way to do what could be done much more efficiently by computer. I am sure that programs will be written to do exactly this, but I am holding off until I have thoroughly hacked the meaning of all these types of message before writing such a program. I am also contemplating the design of a cable to replace the handset, running from the 25 pin connector on the side of my bag phone to a computer.



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