question about this rf/tx module

http://cgi.ebay.com/315Mhz-ISM-RF-Wi...QQcmdZViewItem

"* Type of Output: TTL ( 4 pins output: Vcc, GND, Ant, Data), dummy design. "

above is from the product description. What is dummy design?
Also, how does the tx and rf recognize each other and block out other frequency? If there's another 315Mhz wave, would it interfere with these modules?

?Dummy design? probably means that is very simple to implement the software control.
There are plenty of modules like this on the market, prices ranging from a few bucks to tens.
http://www.udea.com.tr/English/Downloads.htm
http://www.laipac.com/rf-transceivers.htm

regarding RF modules, what does FST stand for?