5V Wireless GSM GPRS SIM800 Module is a small cellular communications module used in electronics projects and embedded systems to add mobile phone network connectivity — specifically GSM (2G) for voice calls, SMS text messages and basic data (GPRS) communication.
Specifcations
Designed to run from a 5 V supply (often USB or regulated DC) and provides the right voltage levels for 5 V microcontrollers.
Communicates via TTL-level serial (UART) interface — so you can control it from an Arduino, Raspberry Pi (with level shifting), STM32, etc.
Has pins for power (5 V, GND), TX/RX serial, SIM card interface, antenna, and reset.
Voice calls (make/receive)
SMS (send/receive text messages)
GPRS data (basic internet/data transfer — slow compared to 3G/4G)
Some boards also include Bluetooth & FM radio support.
Operates on quad-band GSM (850/900/1800/1900 MHz), so it can work in many countries with 2G
Applications
IoT projects — remote monitoring, data reporting
SMS control/alerts — home automation, alarm systems
Remote communication where no Wi-Fi exists
GPRS connectivity for simple data transfers
Embedded systems that need cellular data or messaging