SIM900A GSM Module – Voice Call, SMS, and Serial Communication (TTL UART)

The SIM900A GSM module is a dual-band GSM-based communication board used for sending SMS, making and receiving voice calls, and enabling basic GPRS connectivity. It operates on 900/1800 MHz bands and can be easily interfaced with microcontrollers like Arduino, ESP8266, ESP32, and Raspberry Pi via UART (serial).

The module comes with a SIM card slot, onboard voltage regulators, antenna connector, and TTL-level serial communication pins. It supports AT command set and is widely used in home automation, SMS alert systems, remote monitoring, and other IoT-based applications.

Note: Works only with 2G-enabled SIM cards in supported regions.

Specifications:

• GSM Module: SIM900A

• Frequency Bands: Dual-band 900 / 1800 MHz

• Operating Voltage: 5V (input)

• Communication Interface: UART (TTL – 5V logic)

• Supported Functions: SMS, Voice Call, GPRS (limited)

• SIM Type: Standard SIM (2G only)

• Antenna: External SMA antenna (may vary)

• Baud Rate: Default 9600 bps (configurable)

• Dimensions: Approx. 80mm x 50mm

• Status Indicators: Network & power LEDs