1. Support 2, mobile phone 3, 4G card.

2. The onboard two set power supply interface VCC5 5V power supply, VCC4 interface, 3.5--4.5V power supply, optional power on self starting (default) and control start.

3. The onboard SMA (default) and IPXmini antenna interface, SIM900A interface reserved reset.
4. The computer can give early computer debugging USB module power supply, a very large amount of data under the condition of the recommended current more than 1A.

5. Standby dozens of MA data can be set to provide dormancy, dormancy of 10MA low power.

6. The serial port circuit: support for 3.3V single chip microcomputer. TTL serial port support

7. The SIM card circuit to increase the SMF05C ESD chip.

8. Antenna circuit: guarantee short and straight, so as to ensure the signal strength.

9. PCB display screen printing mark: each interface, convenient development two times, the SIM900/A hardware is completely follow the design when the design manual.

10. A TTL level, compatible with 3.3V and 5V.

11. The two antenna interface, the default SMA straight head, connector for IPXmini antenna.

GND - GND
SIMR SIM900A RXD, TTL level, can not be directly connected to the 232 level
SIMT SIM900A TXD, TTL level, can not be directly connected to the 232 level
RST - SIM900A reset, active low
VCC_MCU when the SIM900A module and 5V TTL level communication, this pin is connected to DC 5V; when the level of communication of SIM900A and 3.3V TTL, this pin is connected to DC 3.3V
VCC5----DC 5V input
VCC4----DC3.5--4.5 input