"Start bells ringing" is a phrase that refers to a sudden realization or recognition of something significant or important. Some possible synonyms for this expression include "trigger an alarm," "ignite a spark," "set off a signal," and "prompt a reaction." Other options might include "awaken awareness," "spark a realization," "provoke a realization," or "raise a red flag." The phrase "start bells ringing" often implies a sense of urgency or active response, suggesting that something important has been brought to attention and action must be taken. Using different synonyms can help to convey different shades of meaning or emphasize particular aspects of this crucial moment of recognition.