Why 10 digits number used for mobile phone?

Answer 1

Early phones started with a set of digits that were usually 2-digits or 3 digits. These numbers were preceded with a word that designated a local area. For example, "Baldwin-445".

Each area used a different word. Therefore, the numbers could be re-used in different areas. For example, "Cadwell-445" and "Baldwin-445" would ring in two separate homes and areas. Local residents often abbreviated the word part to the first 2 letters, which all local residents and operators understood. For example, "BA-445" was meant and understood as "Baldwin-445" in that locality.

By the 1940s through 1960s, more families used home phones (often were still shared lines or "party lines"). The "number" still designated how many rings a home would hear. But with increasing populations, the "personal" part of the number became 4-digits instead of 3-digits, and instead of words at the beginning, local areas were assigned an "exchange".

So, in one city, a region might have several "exchanges" and each resident had a "number" in that exchange. So "Baldwin-445" might have become 4457 with exchanges of 222, 225, 227 (as examples only).

To dial from one State to another required a person to tell an operator the city, then the exchange and personal number. A call to the State of California versus a call to the State of Michigan would be different, even though an exchange and personal number could match exactly in 2 or more States. Eventually they added area codes, but these were NOT used for calls within a local area.

Up until the 1990s, no one had to dial the area code if calling within the local area. Then, the populations of most cities were still increasing, placing a burden on phone companies to create new number combinations. So in the 1990s, every local area needed to dial an area code along with the exchange and personal number.

So, let's say your family lived in a rural Pennsylvania town for the last 110 years.

Your great grandparents may have been assigned the number "55".

Your grandparents may have been assigned the number "555" with a word "exchange" used in front of it, such as Adam-555. At the beginning, the numbers were combinations of 3.

Your parents may have grown up for a time using a number exchange with a personal number, such as 555-555. During this time. the 3-digit numbers became 4-digit, so the number became 555-5555. An "area code" of 3-digits had to be used on State-to-State calls; later, it had to be used on calls in-State between 2 areas. So a number might have been 555-555-5555 and you might call to 666-555-5555.

Your parents and children then had to get used to a further change in the 1990s: all calls placed locally, within a State, or to a different State had to use the area code. So the "telephone number" remained 10 numbers, with a "1" added to indicate "long distance".

Some important notes include:

• Local areas may have had several small "Phone companies". Wires for each company had to transmit sound between the companies. A "phone number" was needed to route the calls to the correct home or business.
• No one was able to "pick" the personal part of the number; that part was assigned, even up through the 1970s-1980s.
• Numbers no longer used by one person or family were (and still are) "recycled". Thirty years to forty years ago, the phone company could keep a used-given-up number out of circulation for 6 months to several years. Now, they recycle formerly used numbers faster.
• Numbers within a phone number can be compared to the "routing numbers" banks use to indicate an area, a bank, and the person's account. If a number is keyed with 1-digit being wrong, it will be routed wrong and arrive at the wrong place.
• All countries have a "Country Code".
• States or main regions within overseas countries have a series of different "area" codes.
• Local areas within USA States or within other countries have "local exchanges". Two different areas with different "area codes" can re-use the same series of numbers in their "exchanges". So, 555-555-5555 is different than 666-555-5555
• A series of "555-555" has always designated a fictitious, non-existent, and non-working number. Television shows and movies, even long ago, often included a "phone number" in their scripts. So actors/actresses needed to use a fictitious number, which was always the "555-5555" series of digits.
• The option to "pick" or choose what number you would like to use is a much recent development, only happening over the last 10 or so years.
• A phone customer was always called a "subscriber", just as if the person was "subscribing" to a newspaper. Subscribers only became "customers" after the 1970s.
• Subscribers could never (and still cannot) pick a phone number that has an area code plus exchange that is for a different Country / State / Region / Local Area.
• The area code "800" began as a way for businesses to provide free lines for customers to call.
• Only businesses could ask for an "800" number.
• Now, non-businesses can request an "800" number.
• The standard "800" that used to designate "tollfree" now includes "888" and a couple others.
• Cellphones follow the same number method-policies as a "land line". Each has an area code plus exchange plus personal number. But subscribers / customers can choose their cellphone number.
• If populations continue to increase, the burden on the phone company--and available numbers--will also increase. This may mean in the future that our USA 10-digit numbers will become longer.

Answer 2

My understanding of your question that you are asking why do cell phones require you to enter a 10 digit number where as a land line will allow you enter a 7 digit number for local phone numbers. The answer for this is simply that cell phone change area codes all the time and by making you continually enter the 10 digit number it removes the need for a lot of processing power in the cell phone systems. So the honest answer is its cheaper for the company and results in better and faster service for you.