Comparison document describing the differences between the SIM900 and SIM300 GSM modules, a 958 KB PDF. It is intended for designers migrating from the older SIM300 to the SIM900, outlining changes in pinout, interface, power supply and AT command behaviour. Technicians find it useful when a board was designed for one module and a replacement of the other type is considered. Read the hardware and software sections carefully, because the modules are not drop-in compatible without checking connector, supply and signal level details.
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