Optical keypad for explosive locations

摘要: An optical keypad for use in hazardous areas and which can ensure safe reliable detection of keystrokes through an at least 8 mm thick glass window, as is required electronics equipment located explosive (In accordance with ATEX Directive 94/9/EC similar requirements) obtained by providing a system 6 LEDs are lit pseudo-random sequence, modulated frequency the interval between lighting each change randomly to avoid interference collocated keypads light from other sources, such daylight artificial light.