The ‘clicking’ of the direction indicator – The emergency lane

Ever wondered why you hear clicking when your turn signal is on? A handy extra to make you aware that it is on, but actually mainly a technical story.

To find out the origin of the ‘clicking’ of the direction indicator, we will start at the beginning of the direction indicator. The first direction indicators of course worked according to a completely different principle. Around the beginning of the 20th century, various carmakers started adding attributes to their cars to clarify the direction of travel. Most common became a “little arm” flipping from the carriage, which in a sense worked the same way as when you put out your hand to indicate where you are going. In the earliest examples, this was simply operated by pulling a lever with a cable attached, which mechanically flipped up the turn signal. It is said that this was inspired by the ‘arm signal’ as it had been used on the railways since the end of the 19th century.

That system could of course be more advanced. To begin with, in the early 20th century, an Italian, Alfredo Barrachini, thought it a good idea to illuminate the direction indicators. After all, in the dark it was otherwise hardly visible which way you were going. The solution was as simple as the pointer itself: Barrachini placed a light in the pointer and laid a power wire for the lighting parallel to the cable that operated the pointer. It was probably already an orange light or it was in an orange housing, because the oldest known unlit indicators were also yellow or orange in color. A logical choice, because it was not to be confused with the headlights or the rear lights. Incidentally, Americans thought differently with their red flashing lights, but that aside.

The folding turn signal with the constantly burning light remained the norm for quite a long time and had certainly not disappeared in a few years when the flashing light was invented. The old-fashioned ‘fold-outs’ remained on some cars at least until the 1950s. However, the flashing light already had its origin in 1933. The American Joseph Bell then applied for a patent on his invention, which he simply called the ‘signaling device’. It was a combination of a ‘traffic light’ and a turn signal, one per side of the car. According to him, you could indicate that you had stopped, by switching on the red light, and indicate your direction by switching on one of the other two lamps. Those lamps flashed to attract extra attention from other road users. In 1938, Bell’s patent application was approved and Buick was the first manufacturer to install turn signals on a car a year later.

As you can see above, it was a unit placed centrally on the tailgate with a flashing light on each side next to the logo. Of course, soon flashing lights followed that were close to the rear lights. At the front, the Buick also had flashing lights at the front for the first time in 1940, which were on top of the front fenders.

But now the question: why do you hear them clicking? Inventor Joseph Bell passed current through a system that contained a spring consisting of two metals. When heated by the electricity, it moved because one metal expanded faster than the other. For example, a thermostat works with a fairly similar principle. Due to the movement of the spring, the power circuit was closed every so often and the lamp came on at the end of the line. This spring was tactically placed, namely behind the dashboard near the driver. After all, on the dashboard, close to this system, there were also lights that showed as an extra safety feature that the indicators on the outside of the car were flashing, then you can of course connect them close to each other. An additional effect was that you could hear the spring jump in the dashboard and voilà: you heard rhythmic clicking at the same pace as the flashing of your indicators.

Later this principle would be followed up by a microchip that triggered an electromagnet to close the power circuit every so often. While that was a more advanced solution, there was still a process taking place in the dashboard that also produced the signature tapping. Flashing lights have functioned like this to this day, although nowadays it is already a purely chip-regulated system in most cars. In most modern cars you therefore hear a clicking sound that no longer sounds really mechanical and that is because it is no longer controlled mechanically. The sound is generated separately, because we simply expect that we can hear the use of the turn signal. After all, it also keeps you sharp whether or not it is turned on.

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