Status report on electronic identification. [Subdermally-implanted temperature indicating transponder for livestock]

A significant milestone was passed in September 1975, with the successful operation of a subdermally-implanted, temperature-indicating transponder having hybrid circuitry. This transponder had no batteries and showed that an implant transponder could be powered by an external microwave beam and transmit encoded temperature information back to the receiver. The encoding of temperature was done because it was very similar to identification, but required much less circuitry. The microwave power levels at the animal skin were well within established safety limits. Additional work needs to be performed on optimizing circuitry and antenna design. (auth)