Why is the United States 9 1 1?

In the era of mechanical dial telephone, the dial will automatically bounce back after rotating. 1 takes the shortest time to bounce back, and 0 takes the longest time to bounce back, one at the head end and the other at the tail end of the dial, which is easy to remember. In the United States, 1 is used to make domestic long-distance calls, and 0 is used to contact operators or make international long-distance calls, so the first digit cannot be 0 or 1.

Therefore, it takes a long time for the number at the end of dialing to rebound, and it takes a long time to hang up in time after dialing the wrong number, so the first number 9 is set. To be on the safe side, to further prevent wrong dialing, just dial two more 1 to confirm the alarm, instead of 999, 990, 900, 90 1.

Related introduction:

As early as 1968, the United States began to use 9 1 1 as an alarm phone. The 9 1 1 incident was that the hijacker deliberately chose the same date and number as the American alarm phone.

In fact, the United States also uses the number 9 1 1. For many Americans, this is an ordinary and kind number. However, because of the "9. 1 1" incident, many complicated emotions were added, and it became the most special number.

1967, the U.S. congress passed a bill, which officially took 9 1 1 as the only national emergency telephone number, breaking the chaotic situation that emergency telephone numbers in various States were not unified.