Features

The R800C GSM/GPRS HAT is a handy, low power Raspberry Pi HAT which features multi-communication functionalities: GSM, GPRS, and phone call,
applicable to countries or regions with 2G network coverage, up to 85.6kbps GPRS speed. It allows your Pi to easily make a telephone call, send messages,
connect to wireless Internet, and so on.

Standard Raspberry Pi 40PIN GPIO extension header, supports Raspberry Pi series boards and Jetson Nano
Supports SMS, phone call, GPRS, TCP/IP, DTMF, HTTP, FTPl, etc.
UART interface, for connecting controller boards like Arduino/STM32
Onboard voltage translator, 3.3V by default, switch to 5V via jumper
2x LED indicators, easy to monitor the working status
SIM card slot, supports 1.8V/3V SIM card
Baudrate: 2400bps ~ 115200bps (115200bps by default)
Control via AT commands (3GPP TS 27.007, 27.005, and SIMCOM enhanced AT Commands)
Supports SIM application toolkit: GSM 11.14 Release 99
Comes with online development resources and manual (examples for Raspberry Pi/Jetson Nano/Ardui/STM32)

Package include

1. R800C GSM/GPRS HAT x1
2. GSM Antenna x1
3. RPi screws pack (2pcs) x1

Resources available: https://www.waveshare.com/wiki/R800C_GSM/GPRS_HAT