Oscillating magnets in coupled coils

Oscillating magnets in coupled coils. A cow magnet suspended by a spring is set to oscillate inside a 1000 turn coil. The coil is connected to an identical apparatus via a reversing switch. As the magnet goes in and out of Coil A, the resulting B-field in Coil B causes Magnet B to oscillate. By changing the reversing switch, the magnets now oscillate 180 degrees out of phase.