Description

Specifications:

• 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.
• The size of the module is 49*50, all the new and original device.
• 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.
• Standby dozens of MA data can be set to provide dormancy, dormancy of 10MA low power.
• Support 2, mobile phone 3,4G card.
• The serial port circuit: support for 3.3V single chip microcomputer.
• TTL serial port support3.3 and 5V single chip microcomputer.
• The SIM card circuit to increase the SMF05C ESD chip.
• Antenna circuit: guarantee short and straight, so as to ensure the signal strength.
• PCB display screen printing mark: each interface, convenient development two times,
  the SIM900/A hardware is completely follow the design when the design manual.
• Two power supply interface: VCC5, 5V DC above 1A.
• Computer 5V power supply can be early computer USB.
• DC long data circuit over larger recommended 5V1A.
• VCC4, 3.5–4.5V power supply, ibid., suitable for lithium battery.
• Control pin all leads.
• A TTL level, compatible with 3.3V and 5V.
• The two antenna interface, the default SMA straight head, connector for IPXmini antenna.
• One way of speech interface, the way Mike interface.

Pin Description:

• GND – GNDSIMR SIM900A RXD, TTL level,
• can not be directly connected to the 232 levelSIMT SIM900A TXD, TTL level,
• can not be directly connected to the 232 levelRST – SIM900A reset,
• active lowVCC_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
• Onboard Resources: Serial port circuit(with protection)
• Antenna interface circuit(SMA bend female port)SIM card circuit
• (flip SIM slot)4*3.5 fixture hole 4pcsSIM900A serial port output terminal
• Size:49mm x 47mm
• Net Weight:28gWeight: 38g

Tutorials:

https://www.instructables.com/GSM-SIM900A-With-Arduino/