SIS is the leading manufacturers of SIM 300 GSM modems offers  lowest price in India;  

Features of SIm300 Module -

��Designed for global market, SIM300 is a Tri-band GSM/GPRS engine
��Works on frequencies EGSM 900 MHz, DCS 1800 MHz and PCS 1900 MHz.
��SIM300 features GPRS multi-slot class 10/ class 8 (optional) and supports the GPRS coding schemes
��CS-1, CS-2, CS-3 and CS-4.With a tiny configuration of 40mm x 33mm x 2.85mm ,
��SIM300 can fit almost all the space requirements in your applications,
��such as smart phone, PDA phone and other mobile devices

Feautures of GSM Kit
��This GSM modem is a highly flexible plug and play quad band GSM modem
��integration to RS232.
��Supports features like Voice, Data/Fax, SMS,GPRS and integrated TCP/IP stack.
��Control via AT commands(GSM 07.07,07.05 and enhanced AT commands)
��Use AC ��DC Power Adaptor with following ratings ��DC Voltage : 12V /1A
��Current Consumption in normal operation 250mA, can rise up to 1Amp while transmission.

Interfaces
��RS-232 through D-TYPE 9 pin connector,
��Serial port baud rate adjustable 1200 to115200 bps (9600 default)
��BRK connector for MIC & SPK, SIM card holder
��Power supply through DC socket
��SMA antenna connector and Murata Antenna ( optional)
��LED status of GSM / GPRS module