For our non-U.S. members who watch American TV shows, have you wondered why just about everywhere seems to have a number that starts 555?

I've posted a brief explanation in the general area that might satisfy your curiosity!
https://www.electrical-contractor.net/ubb/Forum1/HTML/002756.html

I hate to admit this, Paul, but for some years I thought that all telephone numbers in the US started with 555, just like one big area code!.
See what effect TV has on people.

You live and learn!

London had a harder time assigning exchange codes, because the city stuck with the 3-letter, 4-number format. (3L-4N was also used in the early days in some American cities, before they went to 2L-5N, including, I believe, Chicago).

Suitable letter combinations for London were becoming quite tricky to pick for some of the later exchanges, and the GPO sometimes resorted to adopting non-geographic names. They managed to use up a few prefixes by adopting poet's names; for example there was BYRon (297) and KEAts (532). London (and the other five British cities using the 3L-4N scheme) changed over to all-figure numbers in the late 1960s.

For anyone who is remotely curious, here's a list of the London exchange codes prior to going over to all-figure format.

Many of the names are derived from districts of London, e.g. PADington, FINchley, MAYfair. Others were named for particular well-known buildings or landmarks, e.g. MUSeum, serving the area around the British Museum in east central London. The poets I already noted, and some of the others are anyone's guess!

I can't guarantee it's complete, but it gives a good idea of the sort of names that were used.


[This message has been edited by pauluk (edited 04-04-2003).]

Paul,
Do all of the original exchanges still exist?, even with the age of Digital communications upon us?.
How is a modern telephone exchange set out,
as opposed to the old Electro-Mechanical Relay system?.

[This message has been edited by Trumpy (edited 04-09-2003).]

Some of the exchanges were given new prefixes when the letters were dropped, and some were changed in later years, but quite a few of the original codes are still in use.

The situation is a little more complex in recent years due to the numbering plan changing. First, the original 01 London area code was split into 071 for inner London and 081 for outer London in order to double up the capacity. More recently London was put back into a single area code (020) but a digit 7 or 8 added to the old number to make the local numbers up to 8 digits long.

You can still see the original prefixes in many cases, however, e.g. the GERard exchange still serves the same area around Soho, only the numbers are now listed as 7437-xxxx, and the old ENTerprise prefix lives on in New Southgate as 8368-xxxx.

Generally, here in Ireland, and I presume in the UK and elsewhere the old codes that would have originated in the electromechanical system still exsist (obviously people would object to having their phone numbers completely changed just for the hell of it)

Most of our towns and cities had some structure to their numbers. Here it was hierarchiacal rather than using letter codes. e.g. the city centre might be 7 and a particular exchange in the city centre might be 71 or 72 with the subscriber number making up the rest of the number.

New number ranges don't follow the old hierarchical system but they have stuck with the "XXX-YYYY" structure where "XXX" number ranges are given to particular telephone companies and YYYY = subscriber no. XXX doesn't necessarily = a particular exchange though. Typically an exchange might be handling at least 5 or 6 ranges as well as the original "electromechanical range".

If you want to use ISDN direct inward dialling for a business (or whatever) you get assigned an XXX prefix and a range of numbers in YYYY will be your extension numbers.

The future of our national numbering plan is still being debated. They're looking at "closing" it i.e. removing the optional area code and moving to a standard 9-digit system to free up the "1" and "0" in local numbers.

As it is at the moment we have a mix of number lengths (5/6/7 digit local numbers) but it's gradually moving towards a standard (0YX) YXX-XXXX (X = any number) (Y = 2 thru 9) (999 is not permissable). I guess once it's standardised all we'd have to do is drop the leading "0" and we'd close the system.

Another historical surf-by time waster is: http://ourwebhome.com/TENP/Recommended.html and its parent: http://ourwebhome.com/TENP/TENproject.html The first page mentions the “55x” prefix in the US: “In 1955, this was reserved for radio telephone numbers.”

Interesting reading I seem to recall stumbling upon that site some time ago as bits of it seemed familiar.

Bell made it a little easier to assign names by opting for the 2L-5N scheme instead of 3L-4N. The British scheme was also prevented from using names starting with the letter O by having it on zero instead of 6.

DJK,
The old-style U.K. numbering was a real mixture of 3, 4, 5, 6, and 7-digit numbers.

Many small rural exchanges had 3-digit numbers, and with often less than 300 subscribers, chances are that only the 2xx, 3xx, and possibly 4xx ranges were assigned.

4, 5, and 6 digit numbering was usually in progressively larger towns. Many places had mixed length numbers. Certainly from the 1950s through to the 1980s, many medium-sized towns had their original 4-digit numbers in the 2xxx, 3xxx, and 4xxx ranges, with 5-digit numbering as 5xxxx, 6xxxx, and/or 7xxxx.

A trend in later years was for small rural exchanges to be placed into an integrated numbering scheme with its parent exchange. For example, where I once lived the original exchange was named Three Waters and had 3-digit local numbers. It was integrated with the numbering of Truro, the nearest town, and given 6-digit numbers of the form 560xxx. The official exchange name was then changed to Truro, even though the village was still served out of the same central office.

Many other smaller exchanges which "homed" on Truro were integrated in a similar way, and eventually the older 4 and 5-digit numbers in Truro itself were made up to the present-day 6 digits by adding one or two digits in front of the existing number.

7-digit numbering with directors was used only in the major cities: London, Birmingham, Edinburgh, Glasgow, Liverpool, and Manchester.


[This message has been edited by pauluk (edited 04-11-2003).]

Paul:

Over here most of the rural areas were either still manually switched or on old ericsson ARK crossbar exchanges. Very few low population areas had SxS switching.

1979 - 1984/85 all rural areas went to digital switching as small and larger Alcatel E10B exchanges were rolled out. They were mostly 0XX-YXXXX. 5 digit numbering was sufficient in most of these areas. Dublin (01) and Cork (021) only had 6-digit numbering! Dublin migrated to 7-digits in the late 80s and Cork more recently.

Mostly the numbers in 5-digit areas start with 5/4 or 2

As the demand for numbers, due to various telephone companies appearing and the requirment for ISDN Direct inward dial most of the old 5-digit areas were shifted to 7 to free up more structured spac.. They usually just added a 2 digit prefix to the old number. In other areas old area codes were merged to simplify the system.

Paul,
Sorry to briefly change the subject,
but, what sort of phone plug is a BT plug referenced to BS6312?.

BS6312 is the normal plug which has been standard here since the early 1980s. The 4-wire version is known as type BT431A by British Telecom (the 6-wire type is BT631A):



The only problem is that by way of the usual bureaucratic processes, the British Standards Institute managed to number the pins the opposite way round to the original BT standard, e.g. what BSI calls pin 1 is really pin 6!

Now you see why we have definitions such as this:
committee: A life-form with 12 heads and no brain.



[This message has been edited by pauluk (edited 04-14-2003).]

Hear, Hear, Paul!.
Paul, the reason I asked you that, was because we have just had a new Standard come out over here for the Installation of outlets for telephones(2-wire) and for ADSL (Jetstream, it's called over here)installations.
But, what confused me was, the fact that they used the RJ-45(I already know what this looks like)term, but for the Standard outlet for households, there was this: BT to BS 6312 plug, all the way through the Standard, and this was written with the DIY person in mind too!.
Somehow, Paul, I don't like the idea of DIY people fooling around with telephone circuits, especially where the chances of the phone system "accidentally" being inter-connected with the Mains, poses a very real possibility.
What are your thoughts?.

Well, as someone who has spent a lot of time working on telephone lines on poles or in waterlogged manholes, I certainly don't like the idea of somebody injecting 240V onto the line!

I suppose if the DIYers just stick to running extension telephone sockets which aren't integrated with any other wiring systems, then there's little chance of them doing something that drastic.