A radio frequency identification system includes an interrogator for generating and transmitting an interrogation signal to a transponder. One or more transponders of the system receive the interrogation signal and return a data signal which includes identification and/or body characteristic information in one of multiple formats. The interrogator receives the data signal, determines the format of the data signal, and decodes the data signal to obtain the identification and/or body characteristic information. The interrogator operates to decode data signals from transponders not capable of transmitting body characteristic information and transponders which are-capable of transmitting body characteristic information.