Solu SIM900A Extension Module GSM/GPRS 900/1800MHz Board Antenna// SIM900A V4.0 Wireless Data Extension Module GSM GPRS Board Kit with Antenna About us (Solu ), Professional factory of circuit boards, welcome to our store for more choices with best price. What we pursue is your satisfication of our service, not just for our goods.For any reason you are unsatisfied with our product at any time, simply contact support for exchange or refund. we will reply you about any question you ask within 24 hours The serial port circuit: support for 3.3V single chip microcomputer. TTL serial port support Usually, you will get it actually in 9~19 days, If you are in the USA and the item is NOT Fulfilled by Amazon. the item will be sent to you by USPS with shipping information from China. The estimated delivery time offered by Amazon is not the real time. Your patience is highly appreciated. Hope you will receive your item soon and enjoy using it. Antenna interface circuit(SMA bend female port).3.3 and 5V single chip microcomputer. SIM card circuit(flip SIM slot),SIM900A serial port output terminal