Abstract: A communication system for transmitting information by digital binary signaling over an optical channel as a series of light pulses each beginning with a minimum duration and thereafter being variable to represent different binary states. Transmission is between an optical transmitter based on a portion of a display screen in a display device and a photodetector in a signal processing system. Information is recovered by finding averaged sample values, and is evaluated by comparing it against an accumulated averaged sample based threshold derived from the optical signal at a selected intensity. The information received can be used to verify user inputs to the signal processing system.