connect RFID card reader to mini2440

Hi every one.I want to connect RFID reader to mini 2440 as USB serial port.
But when it connected to mini2440, always has beep sound and the led on it
is red then green , then red then green and .....
When I open the "Serial Port Assistant" on mini2440 and connect to
/dev/ttyUSB0 on 9600 baud rate.
then after each beep it sends (0000000000) to mini2440each beep after 1
second occurred.
How can i solve this problem. why this device say beeps and send data
000... repeatedly?( when i put the card on it it sends data correct but
when no card on it, it again says beep after each second and send 000000 to
mini2440)

hello,
     If you want to use RFID , you can use the RFID serial module ,and then
you can  read values of RFID.