|MadSci Network: Science History|
I don't know anything about the history of telephone service in India, but I assume that the reason telephones in India had numbers on their dials and keypads prior to the innovation of text messaging services is due to the history of telephone service in the United States.
Telephone service in the US was originally managed entirely by switchboard operators. Telephone customers would pick up their phones, speak to an operator and tell them the name of the person to whom they wanted to speak. The operator would manually connect the caller to their intended. In the early days of US telephone service (the 1870's), there was no long distance service, and there were only a few thousand telephones (at most) in large cities, so this was a manageable system.
As telephone service became more sophisticated, the numbers of customers increased, and it became increasingly difficult for operators to know the names of all the customers in their exchange area, so 4 digit numbers were innovated to identify specific customers. Note that although numbers were being used to identify customers, human operators were still connecting the calls manually.
In the 1880's, long distance phone service (I think originally between Boston and New York) and automated dialing (using dial phones) were innovated, and by the 1920's manual, local operator- connected calls were replaced by automated switching. Because there very very large number of exchanges, phone numbers consisted of a three character code for the exchange, followed by a 4 digit number specifying the customer. This Bell Telephone Company thought that it would be easier for people to remember what they considered to be long strings of numbers if the exchanges corresponded to names rather than numbers alone, so the exchange code contained 2 letters followed by a number (or sometimes just three letters). These letters were an abbreviation of the name of the exchange.
Here in the US, the primary exchange name that persists in our cultural consciousness is 'Klondike', which was abbreviated KL, and which was actually used in San Francisco. Nowadays, this is used as along with the number 5 (KL5) for 'fake' phone numbers. Another persistent exchange code is 'Butterfield' (BU), made famous by Liz Taylor's movie _BUtterfield 8_. Some other examples of exchanges were Hempstead (HE), Glendale (GL), and Yellowstone (YE), each followed by a number, or the three letter Tremont (TRE). While each of these letter combinations has a set of numbers associated with it, I think that you can see that it might originally have been easier to remember HE4 instead of 434 when you wanted to call your Aunt in Hempstead and you had gotten used to just telling the operator, 'Hempstead please'.
In the 1950's AT&T instituted our modern system of all number calling (aka ANC). This is probably because they were running out of unqiue 3 character codes for exchanges, but also because other nations used different patterns of letters on their dials and keypads (or used a different alphabet, or had no letters on their phones at all), and international telephone calls were increasingly common. In addition, not all letters were included on phones; Q and Z were regularly omitted, or placed on different numbers.
So, the letters on phones were originally put there to help people in the US dial into specific telephone exchanges. However, the legacy of these exchange codes persists to today, and has found new life in the form of text messaging.
You can find all of this information and more by doing a simple google search for the exact phrases, "history of the telephone" and "history of telephone numbers".
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