title: Deference between sim800 and sim900
body: <p>I have developed a card with <code>sim900</code> and <code>ATmel</code>, and it works very well, but when I changed <code>sim900</code> for <code>sim800</code> it did not recognize the sim card.</p>
  
  <p>Difference in hardware design?
  SIM800,SIM800C modem operates from 3.4V to 4.4V supply range (Reduced operating range  !)
  SIM900, SIM900A modules operate from 3.2V to 4.8V supply range.
  SIM800 is having a Pin to connect with Bluetooth Antenna
  Apart from these differences the hardware design is almost similar. The same hardware circuit can be used for the SIM IC if the generated supply is within 3.4V to 4.4V for both types..</p>