[paul.fr]

You know how the number 2 has the letters, a, b and c and so on. When was this 'invented' and what was it's original purpose? Do different countries have different letters on different numbers? why does the number one, have no letters associated with it?

UK number - letters
2, a b c
3, d e f
4, g h i
5, j k l
6, m n o
7, p q r s
8, t u v
9 w x y z

[another_someone]

Oh dear, you youngsters don't remember the days when local exchanges had names.

When I used to live in London (as a child) our phone number (within the London area) was a Maida Vale exchange, and the area code was 624, which if you look at the letters, M = 6, A = 2, I = 4, so the 624 area code represented the 'Mai' that is the start of Maida Vale.  The first two digits of my current area code is 58, and that just happens to match to the letters LU, and the local phone area is Luton (I did not live here in the days when we had names to our phone exchanges, so I am assuming the fact that 58 is LU is not coincidental, but I have only ever known it by the numeric  area code).

I cannot imagine every country has exactly the same letter on the dial pad, since they do not have exactly the same alphabets (I have no idea how a Chinese phone pad looks like).

The main reason I can think of why they would not use the digit 1 for any letters (for any exchange dialling codes) is that back in the days of pulse dial telephones, particularly in the early days, the number you dialled was sent down as a number of pulses (whereas today it is by a series of tones), and the number 1 was represented by a single pulse, and it was too easy for a single pulse to be detected erroneously in consequence to a noise spike (this is also why the emergency services were 999, since the number 9 required 9 pulses, and were least likely to be confused with noise).  In fact, with a bit of diligence, you could dial the phones without using the dials at all, but simply by tapping the appropriate number of pulses at the right frequency on the handset disconnect button (some early public phone boxes, supposedly allowed you to make phone calls without paying for them if you dialled the number in this way).

[paul.fr]

George, that is the most interesting answer i have read in quite some time.
When you say area code, do you mean after 01 or the first digits of the second string of numbers?

[rosalind dna]

I do remember that letter dialing code for the old phones, where you had to
turn the dial instead of touching the number keys as now with the landline or mobile phones.
My parents phone number was this: PRI ******

[another_someone]

George, that is the most interesting answer i have read in quite some time.
When you say area code, do you mean after 01 or the first digits of the second string of numbers?

Yes, I mean after the 01.

[another_someone]

you had to turn the dial instead of touching the number keys as now with the landline or mobile phones.

Indeed, and as the dial returned back to its original position, at a carefully controlled speed, it would pass a switch that would send pulses down the line.  Thus, the number one would trigger the switch once, sending one pulse down the line, the number two would trigger the switch twice, sending two pulses down the line, and the number zero would trigger the switch 10 times as it returned all the way back around the dial, and so sending 10 pulses down the line.

The electromechanical exchanges at the other end would simply move their little arms in response to the pulse, so if it got 10 pulses, they would move down 10 positions to make the connection.

In fact, I wonder how many of the youngsters even know why we talk about 'dialling' a phone number, rather than punching in a phone number (after all, nobody talks about 'dialling' a PIN into an ATM).

[Bored chemist]

"(this is also why the emergency services were 999, since the number 9 required 9 pulses, and were least likely to be confused with noise).  "
Since zero was transmitted as a sequence of 10 pulses, why didn't they use that?
Even now, though a lot of 'phone dialing codes have changed, there are plenty of places where the 'phone numbers correspond to the first few letters of the place name. I work in Buxton and the area code is 01289.

[another_someone]

Since zero was transmitted as a sequence of 10 pulses, why didn't they use that?

After I made the previous post, I too began to wonder that, and have not come up with a completely satisfactory answer.

Yes, there may have been a confusion with the prefixes used for long distance calls (that all start with '0', and maybe they would have been concerned about people repeatedly dialling '0'), but as far as I know, the use of '999' for emergency calls pre-dates the used of STD (subscriber trunk dialling), so that would not then have been a problem.

The three reasons I can think of that might be plausible would be:

1) that '0', being the last digit on the dial, and they might be concerned that people (possibly kids playing with the phone) might dial that inadvertently.

2) Just as a single pulse for the digit '1' might be confused with noise, so too maybe a continuous pulsing could be confused with with the digit '0'.

3) that writing down the digit '0' might easily be confused with the alphabetic character 'o' (which would be the digit '6'), and so using the number '9' was safer to write down.

[Bored chemist]

I think as you sugested, it's because they decided to use 0 as a signal to the exchange to mean "this isn't a local number- please decode it as an area code"
The one thing you don't want an emergency call to do is get routed elsewhere in the country.

Does anyone know why the Americans use 911?

[another_someone]

OK, I've done a little hunting around on Wiki.

Firstly, as I suspected, the use of zero for long distance calling is not pertinent to the 999 phone numbers, since 999 started to be used (initially in London, before being rolled out nationally) in 1937, whereas STD numbers (that allowed intercity calls by prefixing them with zero) did not start until 1958.

One thing that is interesting is that the original numbers used to match the letters of the alphabet was subtly different from what we see at present (shows how bad my memory is):

http://en.wikipedia.org/wiki/Director_telephone_system#Mechanics_and_organisation

It involved a device (the director) which received dialled digits and automatically translated them to route calls between exchanges in the city; in modern parlance a director incorporated a register-translator and a digit store. Directors were applied to step-by-step switching equipment; crossbar and, later, electronic switches of necessity had such capabilities built into them.

Each subscriber was given a seven digit number where the first three digits corresponded to the local exchange name, and were chosen to give the name a meaningful mnemonic. This was done by linking each number on the telephone dial to letters:

• 1
• 2 ABC
• 3 DEF
• 4 GHI
• 5 JKL
• 6 MN
• 7 PRS
• 8 TUV
• 9 WXY
• 0 OQ

Thus a subscriber in Wimbledon could be allocated the number WIMbledon 1234; the first three letters, written in capitals, indicated the code to be dialled. The actual trains of pulses from the subscriber's dial would, of course, be 946 1234. As the code (946 in this example) was the same from any telephone in the London director area, this uniformity is an example of a linked numbering scheme. The code was written in bold capitals if the caller should dial all seven digits. If written merely in capitals it indicated that the desired number was on an exchange which had not yet been converted to automatic working, and that the caller should dial only the code digits, and expect to be connected by an operator. As conversion was completed this difference gradually disappeared.

Thus the confusion between the letter 'O' and the digit zero did not exist.

http://en.wikipedia.org/wiki/999_%28emergency_telephone_number%29#United_Kingdom

The 999 service was introduced on 30 June 1937 in the London area. 999 was chosen because of the need for the code to be able to be dialled from A/B button public telephones. The telephone dial (GPO Dial No 11) used with these coin-boxes allowed the digit '0' to be dialled without inserting any money, and it was very easy to adapt the dial to dial '9' without inserting money. All other digits from 2 to 8 were in use somewhere in the UK as the initial digits for subscribers' telephone numbers and hence could not easily be used. Had any other digits been used, other digits between that one and the already free '0' would also have been able to be dialled free of charge. No other telephone numbers existed using combinations of the digits '9' and '0' (other than one in Woolwich) therefore there would be no unauthorised 'free' calls. Thus the easy conversion of coin-box dial was the deciding factor and the fact that 999 was not used anywhere, other than for accessing the occasional 'position 9' of an Engineering Test Desk in the telephone exchange. Numbers beginning with 1 were excluded for other technical reasons - for example, 111 could be dialled by accident by wires making contact.

It does not say why zero was already free, but my initial guess was that zero may have been the original number for calling the operator (a tradition that has continued for many PABX systems), where this number has now changed to 100.  This would make it a logical number to use as a prefix for STD codes, as it would force people who were used to dialling zero to gain the operators attention in order to place a long distance call to think about using the STD code instead.

[techmind]

You can ignore the "1" as the second digit of the dialling codes as they only added that (to all the numbers in the country) in the early 1990's. They did this in preparation for introducing "020" for London, and to introduce "07" codes for mobiles etc. Once people started having direct-dial exchanges (rather than dialling or asking-for "extensions") at work, they suddenly needed a whole lot more numbers!


As already mentioned, the "0" means "national code follows". On non-London numbers where phone numbers are of the form 01xxx yyyyyy, you can dial just the yyyyyy part to be connected to a number on the same exchange as you are calling from.
The yyyyyy part of the number will never begin with a zero.

For London numbers, 020 xxxx yyyy  then (within London) you can get away with just dialling xxxx yyyy. Again the xxxx part won't begin with a zero.

This all makes sense when you consider the original exchanges were mechanical and hierarchical and progressively connected you closer to your destination as you dialled.

[DoctorBeaver]

Who invented it? The Phonecians!  []

[Paul_1966]

Rather a late response, but here goes!

The idea of using letters on the dial goes back to a time when telephone numbers started to become longer than just a few digits, and it was believed that using a combination of letters and numbers made them easier to remember.  Initially, there was no standard for the use of letters, and there didn't need to be, because direct dialed calls weren't possible outside one's own local area.  Different local telephone companies could - and did - invent their own various unique schemes.  Often they would just put a single letter on each dial position, and numbers might be listed as A-1205, C-5984, etc.  Sometimes these letters were chosen to represent the names of different exchange districts.  To take a hypothetical example, the letters C, S, W, and R might appear on the digits 2 through 5 respectively, with numbers listed as Central 1246, South 2197, West 3118, Riverside 7412, and so on.  Users then dialed the letter plus the four digits.  In some cases, the full names appeared on the dial.  In the U.K., Brighton was one area which used such a scheme in early times, and the dials carried the names Brighton, Hove, Portslade, Preston, Rottingdean, and Southwick on the digits 2 through 7 respectively.

As dial service expanded, it became clear that a more universal system would be beneficial, based upon a standardized set of letters on the dial which could be used to represent exchange names.  In the U.S., a Mr. W. G. Blauvelt of AT&T is generally credited as being largely responsible for the adoption of the system, around the time of World War I, resulting in the now-familiar assignment of letters on North American dials:

2 - ABC
3 - DEF
4 - GHI
5 - JKL
6 - MNO
7 - PRS
8 - TUV
9 - WXY

No letters were assigned to 1 or 0, since the former was not used as the first digit of a telephone number due to the risk of false impulses, and the latter was reserved for reaching an operator.  Q and Z were omitted, although Z did make an appearance in the zero position of some dials in later years, but was dropped again at the end of the 1940's. 

Several different numbering schemes were employed in those earlier times.  As well as a single-letter-plus-number scheme as already mentioned, a common format which soon became widely used was 2L-4N (i.e. numbers were two letters representing the exchange name, followed by four numbers), giving rise to numbers such as SUnset 4508 or DUpont 6200.   For many years, Los Angeles and Washington D.C. had numbers in this format.

Larger American cities which needed 7-digit numbering most often adopted a 2L-5N format, but a few initially used 3L-4N, changing to 2L-5N later.  New York and Chicago fall into the latter category, changing formats in 1930 and 1948 respectively. 

The 2L-5N format was to become the norm when numbers across the country were made up to seven digits for the uniform direct dial plan, and you'll see many references to numbers in this format in movies and TV shows of the appropriate era, not to mention Glenn Miller's famous recording of PEnnsylvania 6-5000, referring to the telephone number of the Hotel Pennsylvania in New York City.

Here in Britain, the G.P.O. adopted the same basic lettering scheme on the dial, with the single exception of moving the letter "O" onto the zero position, as already noted above.  London used a 3L-4N numbering system, giving rise to numbers such as HOLborn 1234, MAYfair 5678, and the famous WHItehall 1212 (the main number for Scotland Yard for many years).   A similar 3L-4N system was adopted in Birmingham, Edinburgh, Glasgow, Liverpool, and Manchester, but elsewhere numbers were entirely numeric (after those very early schemes such as Brighton's were eliminated).

Other countries often used similar schemes, but with appropriate changes to the letters on their dials to suit the local language.  In France, for example, Paris used the same 3L-4N numbering scheme as London, and the letters on dials were similar to those on British dials, but with Q added to the zero position (the city had an exchange named ROQuette).  In other countries, the letters assigned to the various digit positions were quite different.

In general, letters as part of the phone numbers vanished during the 1960's, London making the change to 7-digit all numeric numbers during the 1966 to 1968 period.  A few American cities maintained letters in numbers through into the 1970's, however.

There were two main reasons for abandoning letters.  First, it was becoming increasingly harder to come up with suitable exchange names to fit vacant codes.  Try making up any sort of meaningful exchange name (in English!) from the letters available for the codes 559 or 956, for example.  This is what had already prompted cities like New York to change from 3L-4N to 2L-5N, since needing only two letters instead of three made many more choices available.  Switching to all-figure numbering made all of those otherwise difficult-to-name codes available, which was important at a time when telephone use was expanding rapidly.

Second, international direct dialing was starting to become a reality, and the various incompatible schemes on different countries' dials made it impossible for somebody in one country to dial numbers involving letters in another country.  The letter Q was actually added to British dials ready for when direct dialing to Paris became available from some places in 1963.  That was relatively easy, since all the other letters were identical.  But for calls between, say, the U.K. and the U.S., there was the problem of the letter O being on a different digit.  The London number ACOrn 1234 was 220-1234 on a British dial, but anyone using an American dial would end up reaching CANonbury 1234 (226-1234) instead.   Obviously the problems with countries using vastly different dial letters were even more severe.

To address a few other points:

The first two digits of my current area code is 58, and that just happens to match to the letters LU, and the local phone area is Luton (I did not live here in the days when we had names to our phone exchanges, so I am assuming the fact that 58 is LU is not coincidental

It certainly isn't.  The original U.K. STD plan assigned the bulk of the codes on the basis of two letters plus a number, the letters representing the town name, or sometimes some form of the county name or some other geographical reference.  Hence, to take a few examples:

0AB4 = 0224 = Aberdeen
0BE4 = 0234 = Bedford
0BR2 = 0272 = Bristol
0NO3 = 0603 = Norwich
0PE6 = 0736 = Penzance
0SW2 = 0792 = Swansea

The exceptions to this general rule were London which was assigned just 01, and Birmingham, Edinburgh, Glasgow, Liverpool, and Manchester which were assigned 021 through 061 respectively (if you look at those codes, the first digit after the zero also happens to correspond with the name of the city, although these codes were always listed as numeric only).

As with local exchange names in London and the other large urban areas, the letters were dropped from the STD codes later in the 1960's, leaving them in the all-number form with which people are familiar today (allowing for the later insertion of "1" etc.).

Does anyone know why the Americans use 911?

See http://www.thenakedscientists.com/forum/index.php?PHPSESSID=ea40a3b14881d3ebfb988be6417daaa5&topic=35127.0 [nofollow]

It does not say why zero was already free, but my initial guess was that zero may have been the original number for calling the operator (a tradition that has continued for many PABX systems), where this number has now changed to 100.

Zero was indeed the number to reach the operator from the early days in dial service.  In Britain, the operator was moved to 100 in preparation for STD and the use of zero as the STD access prefix.

[alancalverd]

The original question seems to have been answered pretty thoroughly, but here's a nice aside.

The international prefix from France used to be 19, quite unlike any other country (naturellement) but "entirely by coincidence" it meant that dialling the UK from France required the prefix 1944. Mysteriously, European "rationalisation" changed the prefix to 00, but many years after a significant political point had been made.