Surface acoustic wave touch screen

The Touch surface wave has transmitting and receiving piezoelectric transducers for the X and Y axes mounted directly on the faceplate.
The controller sends five-megahertz electrical to the transmitting transducer ,which converts the signal into ultrasonic waves within the surface of the glass .these wave are directed across the faceplate by an array of reflectors .Reflectors on the opposite side gather and direct the waves to the receiving transducer ,which reconverts them into an electrical signal .the process is repeated for each axis.
When you touch the screen,you absorb a portion of the waves traveling across it .the received signals for X and Y are compared to the stored digital maps ,the change is recognized ,and a coordinate is calculated .