Transmit sound by modulating infrared light. The transmission can be interrupted by placing your hand in the slot provided. The infrared light is visible by using a camera on a cell phone.
Fiber Optic Data Transmission
By the press of a button data is transferred from one point to another via fiber optic cable. The modulated laser is visible in a spot where the sheath has been removed. The laser modulation can clearly be seen in the lower enlarged simulation of the fiber optic principle.