Have terrible with RFID, i need help!

hello,

I new arduino programmer, I builded a few programs that turn on/off light in my bedroom by my iphone and etc.

I have decided to build an program that receives cardID (I mean RFID) to my room's door, my friend give me a program with it's hardwares and it's work fine, but i want to build my own program with arduino.

First of all, the RFID that i have work with 12V power. when i connect it to my arduino (rx,tx), and compiled it, the serial monitor display "FFFFFFFFFF" ( I mean all the cards give me the same result).

I bought a new RFID (company name: CROW systems), also have a 12V power. I tried to connect it to my arduino and read the serial, the serial monitor also display "FFFFFFFFFF".

After deep searching in google, i found that there is two types of RFID: 1) UART 2) Wiegand

Can someone answer my questions: 1) how can i know my RFID type? 2) why always serial.read() return "FF" 3) the problem is 12V power to the RFID? 4) if i replaced rx with tx, what i get. and what is the rx and tx? 5) can i get a sample code to try it? 6) it's correct to get serial.available() = [1,A,9,8,7,6,5,4,3,2,1] ? 7) can i connect the RFID direct to the USB, and get data in visual studio C#?

Thank you, David Antoon

I need help please. I have a university tinal project ! Anybody can help me? I want asnwers to my questions .

Thank you, David Antoon