An apparatus for use in an electrographic position sensing system comprises an antenna system and a signal strength detector. In one embodiment, the antenna system comprises two antennas. The detector measures the signal strength from each antenna. A microprocessor contains an algorithm to calculate...http://www.google.com/patents/US6661405?utm_source=gb-gplus-sharePatent US6661405 - Electrographic position location apparatus and method
Electrographic position location apparatus and method
