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.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.The control interface of each 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.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 Dimensions & Weight: 5.6 cm x 4.9 cm x 2.8 cm/23 gPacking List : 1 x GPRS GSM Module1 x Antenna 1 x Cable (10cm)
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