interfacing EM18 RFID reader module

parallax reader has "enable" pin but EM 18 has only 3 pins Tx,Vcc,Gnd . The program on interfacing rfid in arduino website uses "enable" pin how can i do with EM18. pls help

please post a link to the website describing the device - datasheet!

One possibility is that the EM18 is continuous enabled, ?
I don't know if the TX is on TTL level or on RS232 level., ?
I don't know how much power the EM18 needs, ?
...
So a link to the datasheet is really needed !