Why don’t cell phones have a dial tone? — Ask Your Science Teacher

Answer: The dial tone is used to let the telephone user know that a signal is available, and that the system is working. If no dial tone, no call can be placed.

Most cell phones have those little bars that informs the owner of the signal strength. If the cell phone is out of range of a cell tower, the cell phones usually display something like “network unavailable” or “no service” on the screen.

Keep in mind that even when you are not using your cell phone, it remains “on.”

The cell phone is a receiver, just like a radio receiver, but with the volume turned down.

The cell phone is listening for any calls that might come in. A cell phone is “off” only when a person turns the power off.

Early telephone systems all had a telephone operator, a live person. Remember those Andy Griffin shows. Sheriff Andy Taylor would take the earpiece off the hook, and say into the separate mouthpiece, “Sarah, get me Mt. Pilot” or Barney Fife would say, “Sarah, ring me Juanita at the Bluebird Diner.”

When telephone operations were automated, the automatic tone indicated the system was ready to be used. The British were the first to use a dial tone. The tone indicated that the telephone exchange was working, the receiver had been taken off the hook, and the telephone receiver is ready to talk into. The dial tone quit when the first number was dialed.

The U.S. started using dial tones in the late 1940s. Widespread use came in the 1950s. There is a story about President Dwight Eisenhower leaving the White House in 1961. He retired to his farm a tad south of Gettysburg, Pennsylvania. When he picked up his house phone, he didn’t know what that strange noise was. One of his aides had to explain the dial tone to the former president, and also how to use a rotary phone.

Modern dial tones in the U.S. are a blend of two frequencies, tones, or pitches. One is 350 Hz and the other is 440 Hz. In Europe it is a single tone of 425 Hz.

That 440 Hz dial tone has been used by stringed concert musicians to tune their instruments. In music, the A above middle C is written as A440.

Touch tone dialing, the current standard in the industry, started in 1963. Each number from 0 to 9, plus the star, pound, and A, B, C, and D buttons use two tones out of a possible eight. The lowest is 697 Hz and the highest is 1209 Hz. For example, when you hit the 6 button, you hear a combination of 770 Hz and 1477 Hz.