Features: Computer debugging USB--TTL. This module is powered by: 5V-26V, 5V 2A power supply is recommended. After plugging in the motherboard, the power supply must be able to supply 2A. The reason is that the GPRS module startup current and the maximum top current required to work up to 2A, but the USB port can not provide such a large current, so the external power supply equipment must be provided. The other power supply port leads to the 3.7--4.5V power supply for lithium battery power supply. The serial port is perfectly compatible. The TTL serial port is compatible with 3.3 and 5V microcontrollers. Make sure your SIM card is not locked. The best baud rate for GPRS communication is 19200 BPS 8-n-1 (GPRS module automatically matches baud rate by default). Quad-Band 850 / 900/ 1800 / 1900 MHz - would work on GSM networks in all countries across the world. GPRS multi-slot class 10/8. GPRS mobile station class B. Compliant to GSM phase 2/2+. Class 4 (2 W @ 850 / 900 MHz). Class 1 (1 W @ 1800 / 1900MHz). Control via AT commands - Standard Commands: GSM 07.07 & 07.05 | Enhanced Commands: AT Commands. Short Message Service - so that you can send small amounts of data over the network (ASCII hexadecimal). Embedded UDP stack - allows you to upload data to a web server. RTC supported. Selectable serial port. Speaker and Headphone jacks. Low power consumption - 1.5mA(sleep mode). Specification: Power Supply:5~26V Four Frequency Range:850/900/1800 / 1900 MHz Working Temperature:-40~85℃ Package List: 1 x Module 1 x GSM Antenna Note: The product is provided as is without an insulating enclosure. Please observe ESD precautions specially in dry (low humidity) weather. The factory default setting for the GPRS module UART is 19200 bps 8-N-1. (Can be changed using AT commands). Interface Introduction: Power select - select the power supply for GPRS. Power jack - connected to external 4.8~5VDC power supply. Antenna interface - connected to external antenna. Serial port select - select either software serial port or hareware serial port to be connected to GPRS module. Hardware Serial - D0/D1. Software serial - D7/D8. Status LED - tell whether the power is on. Net light - tell the status about linking to the net. UART of UART pins break. Microphone - to answer the phone call. Speaker - to answer the phone call. GPIO,PWM and ADC of GPIO,PWM and ADC pins break. Power key - power up and down. .