SIM900A GSM / GPRS Modem (TTL with Serial Interface)

This is a GSM Modem with a simple to implement RS232, TTL Serial, Use it to send SMS, make and receive calls, and do other GSM operations by simple AT commands through a serial interface from microcontrollers and computers. It uses the highly popular SIM900A module for all its GSM operations. It comes with a standard RS232 interface which can be used to easily interface the modem to microcontrollers and computers. The modem also features a serial TTL interface option. All modem operations(sending and receiving messages, calls, etc) can be carried out by sending AT commands to this virtual serial port through a serial terminal program. Most programming languages allow sending and receiving serial commands to a serial port and can be used to write softwares that can operate the modem without the need to implement any complex interface. This makes the modem a great choice if you plan to use GSM features on a computer.SIM900A.

Specifications:

• Power supply: Single supply voltage 9V to 12V(DC).
• Onboard power ON and Network indication LED.
• Onboard provision to select the power on mode of SIM900A (manual or auto) using a jumper.
• RS232 output to connect directly to computer.
• Serial TTL onboard pin to directly connected to microcontroller.
• Onboard Audio(speaker and microphone) interface pins.
• Onboard pwm and ADC channels.  Resources: SIM900A Modem