GSM stands for Global System for Mobile communication. It is a digital cellular technology used for transmitting voice and data services.GSM operates on a mobile communication band 900mhz and 1800mhz, it operates on 850mhz and 1900mhz.GSM uses narrowband Time Division Multiple Access (TDMA) technique for transmitting signals.
- GSM has a different configuration :
- Sim300 is a triband GSM modem it can operate at three frequency 900mhz,1800mhz,1900mhz band.
- Sim900 is a quadband GSM mode it can operate at four frequency 850mhz, 900mhz,1800mhz,1900mhz.
- Sim900a is a dual-band GSM mode it can operate at two frequency 900mhz,1800mhz.
- AT commands used to control the modem.
- In GSM mode for each function like make a call and to send the message, to access the internet, there is a set of AT commands used to activate the function.
AT SMS Commands
- GSM Module.
- Atmega16 Microcontroller.
- Vin= +5V.
- Tx= Rx of Microcontroller.
- Rx= Tx of Microcontroller.
- Gnd= Ground.