So, that device appears to be an RS232C device. RS232C devices are not compatible with TTL serial data. You need a MAX232 chip, or equivalent, between the Arduino and the RFID device, before you destroy your Arduino.
So, that device appears to be an RS232C device. RS232C devices are not compatible with TTL serial data. You need a MAX232 chip, or equivalent, between the Arduino and the RFID device, before you destroy your Arduino.