Touch screens use different technologies to locate the coordinates of a user's touch. Resistive touch screens use two resistive layers that complete a circuit when touched. Capacitive screens use conductive layers and detect voltage changes from a finger touch. Surface acoustic wave screens transmit and receive ultrasonic waves across the screen. Infrared/optical screens use LEDs and cameras to detect interrupts from touches. Resistive is most affordable but less durable, while capacitive is more expensive but supports multi-touch. Surface acoustic wave and infrared provide best optical quality and multi-touch support but are most expensive.