Series 04 Switch Range EAO Series 04 Switch Range includes push-buttons, indicators, selectors, illuminated selectors, mushroom-headed switches, key switches, buzzers, stop switches, and emergency stop switches. EAO emergency stop switches offer an additional level of protection in emergency situations with available fail-safe contacts. Modular assembly can lead to thousands of possible switching configurations. These durable, rugged, and robust products are offered in a variety of materials and can withstand the most aggressive environments ranging from transportation applications, to machinery, to public use, to medical equipment.