Method for transmitting message containing predetermined duration of message from batteryless transponder to interrogator

PURPOSE: To obtain information concerning to an animal by an arrangement wherein a high frequency interrogation pulse for requesting transmission of a message can be transmitted to a transponder in response to an interrogation command validated in an interrogator. CONSTITUTION: Assuming a limited area, e.g. a pigpen, a large number of animals can stroll freely therein. Interrogators for transmitting a high frequency pulse at a constant interval are set fixedly at several points. The interrogator can receives a message through an antenna 10, demodulate the message and evaluate the message in a processor 22. A transponder has a carrier frequency identification circuit 24 in order to prevent transmission of a high frequency interrogation pulse at a moment of time when another interrogator just retains a response from the transponder and notifies presence of another carrier frequency signal. Consequently, the processor 22 actuates a high frequency interrogation pulse source only thereafter. COPYRIGHT: (C)1991,JPO