is it possible to use the phone without a sim card or change the frequency at which the mobile communicates.. actually what i want to do is use a couple of cell phones or more to communicate between each other over a short range without using any service provider, i am ready to buy/make a kit which can work as a kinda service provider between those two or more mobiles in a certain region.. say of radius 300-500m......
on more larger scale.. i want to set up a kind of inter-com system using cell phones which people already have.. as of now.. the cell phones models are not important.. i just want to tweak them for my purpose
any suggestions, links or books will be very very helpful......
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