Feature: There are two built-in power interfaces: VCC5 5V power supply, VCC4 interface, 3.5-4.5V power supply, optional self-start (default) and control start. Built-in SMA (default) and IPXmini interface, SIM900A interface is reserved for reset. The module size is 49*50, all of which are brand new and original. The computer can power to an early computer to debug the USB module. When the recommended current is more than 1A, the amount of data is very large. Dozens of MA data in standby mode can be set to provide sleep, 10MA low sleep power. Support 2, Mobile Phone 3, 4G card. Serial port circuit: support 3.3V microcontroller. Serial TTL port support3.3 and 5V microcontrollers. The SIM card circuit adds the SMF05C ESD chip. Antenna circuit: keep it short and straight to ensure signal strength. PCB display silk monitor sign: each interface is convenient for secondary development, SIM900/A hardware is completely designed according to the design manual. Two power interfaces: VCC5, 5V DC above 1A. The 5V computer power adapter can be used in an early USB computer. If the DC data circuit is too large, 5V1A is recommended. VCC4 power supply, 3.5-4.5V, same as above, suitable for lithium battery. Control pins for all wires. TTL level, compatible with 3.3V and 5V. Two antenna ports, default SMA straight head, IPXmini antenna connector. Description of each pin control interface: Ground-to-ground SIMR SIM900A RXD, TTL level, not directly connected to 232SIMT SIM900A TXD level, TTL level, not directly connected to 232Rst-sim900a reset, active niskiVCC_MCU when the SIM900A module communicates with 5V TTL level, this pin is connected to DC 5V; When the SIM900A communicates with the 3.3V TTL level, this pin is connected to the DC 3.3V. VCC5-DC 5V input. VCC4-DC3.5-4.5 input Onboard Resources: Serial Port Circuit (With Protection) Antenna Interface Circuit (SMA Curved Female Port)SIM Card Circuit (Invert SIM Card Slot)4*3.5 Luminaire Hole 4pcsSIM900A Serial Port Output TerminalSpecification:Color as shownDimensions: 49mm x 47mmNet Weight: 28g Weight: 38gPackage Included:1 x SIM900A Kit1 x Power Cord1 x AntennaNotes:1. Due to manual measurement, please allow 1-3mm error.2. Due to the difference of different monitors, the picture may not reflect the actual color of the item. Thanks!