The phrase "switches on" can be substituted with various synonyms depending on the context of the sentence. Some synonyms that can be used include activates, powers up, turns on, starts up, ignites, initiates, triggers, launches, executes, commences and kickstarts. Whether you're talking about a start-up company or a simple light switch, there are plenty of synonyms you can use to add variety to your writing. It is always important to choose the correct synonym that will convey the intended meaning within the context of the sentence. By using different synonyms, you can make your writing more engaging and avoid repetitive language patterns.