Personnel safety utilizing time variable frequencies

A system to improve safety of workers being in proximity to mobile machines comprising:

• a machine mountable radio-frequency identification reader that wirelessly monitors radio-frequency identification tags worn by workers moving relative to and in proximity to a mobile machine when said reader is mounted on the machine wherein said reader includes a processor and a antenna front-end which is switchable between an omni-directional antenna and at least one directional antenna, and wherein said omni-directional antenna is mountable so as to monitor a machine circumference completely around the mobile machine, and wherein said at least one directional antenna is mountable so as to monitor only either a front or a back of the mobile machine relative to the machines direction of motion, and wherein said processor determines location of said tags which are not in said front or back by comparing whether detected tags are detected by only said omni-directional antenna and not said at least one directional antenna,
• wherein said reader is programmable to monitor multiple fixed or variable detection zones and wherein said tags include alarms and are adapted to trigger said alarms to alert workers wearing said tags when said tags are detected by said reader within said detection zones,
• and wherein each said tag is integrated with a corresponding upper-body garment wearable by a worker and each said tag includes a discreet first garment antenna and a discreet second garment antenna mounted to said garment at substantially the shoulder level of said garment, wherein said first and second garment antennas are oppositely disposed on said garment so as to provide for 360 degree line-of-sight monitoring of said tag in a complete 360 degree circumference around said tag by said reader when a worker wearing said garment moves into a line-of-sight position within said detection zones,
• and wherein said wireless monitoring of said tags by said reader uses a chirp spread spectrum technique so as to provide high noise and multi-path resistance,
• and wherein said reader is adapted to at least partially disable movement of the mobile machine upon detection of at least one of said tags within a reaction zone within said detection zones and upon said processor thereby determining a probability of collision between the mobile machine on which said reader is mounted and at least one of said tags.