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.
The onboard SMA (default) and IPX mini antenna interface, SIM900A interface reserved reset.
Standby dozens of MA data can be set to provide dormancy, dormancy of 10MA low power.
The serial port circuit: support for 3.3V single chip microcomputer.