Mysterious Thread Phone Kelvin; Farmer - Bob Chad This feature has many uses

This feature has many uses for magic

At an IBM conference

yet so perplexing and with just a couple of cards

(video link with explanation)

Depicted Pieces:

Mysterious Thread Phone Kelvin; Farmer - Bob Chad This feature has many usesIt is a unique and clean phenomenon using a thread phone. Fill one cup with a coin and hold the other cup upside down. When you play with a yarn phone, you have to taut the thread, and when the thread is stretched vertically, the coin appears from the cup on the opposite side. There is nothing left in the cup with the coin in it. At first glance, you don't feel the existence of a gimmick, but the simple and rational gimmick set up in the yarn phone