DEVICE FOR INDICATING "OFF SIDE" POSITION IN FOOTBALL GAME Russian patent published in 1995 - IPC

FIELD: sports equipment. SUBSTANCE: tenon is mounted into sole of football boot. The tenon is made on non-magnetic material. There is a magnet in internal surface of the tenon; the magnet is connected with top and power walls of the tenon by means of springs. Rigidity of the springs is chosen in such a manner that when players move along the field, magnets in their boots will oscillate with frequency f₁, and magnets of players from the other team will oscillate with frequency f₂. Oscillating magnets excite currents with frequencies f₁ and f₂ in inductance coils which are put under the surface of the field at specific order. EFFECT: improved quality of judging. 6 dwg, 1 tbl