Digital bargraphs measure process and electrical variables such as pressure, flow, temperature, speed, current, and voltage. There are two main types of products: light emitting diode (LED) and liquid crystal display (LCD). LED bargraphs consist of rows of tiny light bulbs that are illuminated by the movement of electrons in a semiconductor material. They present data digitally and use vertical or horizontal segments to indicate the degree of information displayed. Some digital bargraphs position the zero point at the end of the bargraph. Others place the zero point in the middle, displaying negative values on the left and positive values on the right. Most programmable, indoor-rated LED bargraphs use all red LEDs, or a combination of red and green LEDs to create 256 colors. Blue LEDs provide the highest degree of brightness and, when combined with red and green LEDs, can provide up to 1.7 million colors. Standard display colors for LED bargraphs also include amber, aqua, green and orange. High-intensity red LEDs with a common wavelength of 700 nm are also available.