The SIM900A GSM Module is a compact, cost-effective, and reliable communication solution developed by SIMCom Wireless Solutions for IoT, M2M, and embedded applications. This article will discuss the SIM900A GSM Module’s features, specifications, applications, and more.

The SIM900A GSM Module is a compact and reliable GSM/GPRS solution designed for IoT, M2M, and embedded applications. It supports dual-band frequencies (EGSM 900 MHz and DCS 1800 MHz), ensuring broad network compatibility. With a built-in TCP/IP stack, it allows seamless internet connectivity through simple AT commands, making it ideal for remote data transfer, telemetry, and control systems. Its small 24 x 24 x 3 mm form factor makes it suitable for space-limited devices such as smart meters, tracking systems, and handheld equipment.
Engineered for efficiency, the SIM900A consumes as little as 1.5 mA in sleep mode, extending battery life in portable applications. It offers a 68-pin SMT interface, providing flexible connections for serial communication, audio, keypad, and GPIO functions. Easy to integrate and cost-effective, it remains a trusted module for reliable wireless communication.
If you are interested in purchasing the SIM900A GSM Module, feel free to contact us for pricing and availability.

| Pin No. | Pin Name | Description |
| 1 | PWRKEY | Power on key input |
| 2 | PWRKEY_OUT | Power key output |
| 3 | DTR | Data terminal ready |
| 4 | RI | Ring indicator |
| 5 | DCD | Data carrier detect |
| 6 | DSR | Data set ready |
| 7 | CTS | Clear to send |
| 8 | RTS | Request to send |
| 9 | TXD | Transmit data |
| 10 | RXD | Receive data |
| 11 | DISP_CLK | Display clock signal |
| 12 | DISP_DATA | Display data signal |
| 13 | DISP_CS | Display chip select |
| 14 | DISP_DC | Display data/command control |
| 15 | VDD_EXT | External 2.8V output |
| 16 | NRESET | Module reset input |
| 17 | GND | Ground |
| 18 | MIC_P | Microphone positive input |
| 19 | MIC_N | Microphone negative input |
| 20 | SPK_P | Speaker positive output |
| 21 | SPK_N | Speaker negative output |
| 22 | LIN_P | Line input positive |
| 23 | LIN_N | Line input negative |
| 24 | ADC | Analog-to-digital converter input |
| 25 | DBG_TXD | Debug transmit |
| 26 | DBG_RXD | Debug receive |
| 27 | SIM_VDD | SIM card voltage supply |
| 28 | SIM_DATA | SIM data signal |
| 29 | SIM_CLK | SIM clock signal |
| 30 | SIM_RST | SIM reset signal |
| 31 | SIM_PRESENCE | SIM card presence detection |
| 32 | SDA | I2C data line |
| 33 | SCL | I2C clock line |
| 34 | PWM1 | Pulse width modulation output 1 |
| 35 | PWM2 | Pulse width modulation output 2 |
| 36 | GPIO1/KBR0 | GPIO or keypad row 0 |
| 37 | GPIO2/KBR1 | GPIO or keypad row 1 |
| 38 | GPIO3/KBR2 | GPIO or keypad row 2 |
| 39 | GPIO4/KBR3 | GPIO or keypad row 3 |
| 40 | GPIO5/KBR4 | GPIO or keypad row 4 |
| 41 | GPIO6/KBC0 | GPIO or keypad column 0 |
| 42 | GPIO7/KBC1 | GPIO or keypad column 1 |
| 43 | GPIO8/KBC2 | GPIO or keypad column 2 |
| 44 | GPIO9/KBC3 | GPIO or keypad column 3 |
| 45 | GPIO10/KBC4 | GPIO or keypad column 4 |
| 46 | GPIO11/KBC5 | GPIO or keypad column 5 |
| 47 | GPIO12/KBC6 | GPIO or keypad column 6 |
| 48 | GPIO13/KBC7 | GPIO or keypad column 7 |
| 49 | STATUS | Module status output |
| 50 | NETLIGHT | Network indicator output |
| 51 | ANT | Antenna connection |
| 52 | VBAT | Power supply input |
| 53 | VBAT | Power supply input |
| 54–68 | GND | Ground |
| Module | Network Type | Frequency Bands | Key Features | Use Case |
| SIM800L | 2G GSM/GPRS | Quad-band (850 / 900 / 1800 / 1900 MHz) | Small size, low power, built-in TCP/IP | Direct upgrade to SIM900A, suitable for IoT and GSM-based communication |
| SIM900 | 2G GSM/GPRS | Quad-band (850 / 900 / 1800 / 1900 MHz) | Similar AT command set, TCP/IP stack | Almost identical to SIM900A but with wider global network compatibility |
| SIM808 | 2G GSM/GPRS + GPS | Quad-band (850 / 900 / 1800 / 1900 MHz) | GPS tracking + GSM functions | Ideal for vehicle tracking and navigation projects |
| SIM7600E / SIM7600G | 4G LTE / 3G / 2G fallback | Multiple LTE bands | High-speed data, GNSS, SMS, voice | Future-proof option for IoT and industrial data systems |
| QUECTEL M95 | 2G GSM/GPRS | Quad-band (850 / 900 / 1800 / 1900 MHz) | Compact, efficient, TCP/IP, extended temperature range | Reliable alternative for industrial GSM connectivity |
| SIM7600G-H | 4G LTE (Cat 4) | Global LTE bands | Fast data rate, GPS, SMS, voice | Advanced IoT systems requiring 4G performance |
| SIM7080G | LTE Cat-M / NB-IoT / 2G fallback | Multiple LTE-M/NB bands | Low power, global connectivity, integrated GNSS | Best for modern low-power IoT applications |
| Siemens MC55 / MC46 | 2G GSM/GPRS | Dual / Tri-band | Stable and legacy-supported module | Suitable for older GSM-based systems still in operation |