Your turn signal clicks because a speaker fakes it

Today's turn signals tick for three reasons, none of them electrical: habit, warning and marketing. Behind the sound there's a hidden speaker, not a relay: the click is copied on purpose. Three reasons why it's still there.

1. Habit. Mechanical turn signals from the 1930s used a bimetallic flasher: a strip that heated as current passed, bent, cut the circuit and, when cool, closed it again. The little metallic snap came from that whip. In a 1963 Volkswagen Beetle it came out of the dashboard housing.

2. Warning. When electronics replaced the relay in the 1980s, many cars started signalling in silence. Drivers were soon found to leave the indicator on for miles. European rule ECE R48 has required since 1988 that the driver be told the signal is on by optical or acoustic means.

3. Marketing. Each brand picked its own tone. Toyota emits it at about 1.5 Hz, BMW slightly lower. In 2018, Rolls-Royce recorded its tick in a studio with a film sound engineer and calls it the heritage click. It's still a hidden speaker behind the dashboard. None of them touches a relay.