In message ,
Martin Underwood writes

By the way, how did changing from 0171 xxx yyyy or 0181 xxx yyyy to 020 7xxx
yyyy or 020 8xxx yyyy help alleviate the shortage of available numbers in
London? It didn't increase the number of available phone numbers - all it
did was to change the mapping slightly. OK, so there's scope for additional
district codes beginning with digits other than 7 or 8, but it's not
districts that are in short supply, it's subscriber numbers (the xxxx in the
above example).

Just to add to John's reply, London numbers starting with 020 3xxx are
due to start being allocated this summer. Unlike 020 7xxx and 020 8xxx,
they will be assigned on a London-wide basis and will not be mapped to
any particular district within London.
--
Paul Terry

"Paul Terry" wrote in message
...

Just to add to John's reply, London numbers starting with 020 3xxx are
due to start being allocated this summer. Unlike 020 7xxx and 020 8xxx,
they will be assigned on a London-wide basis and will not be mapped to
any particular district within London.

Which, AIUI, was supposed to be the case with unallocated 7xxx and 8xxx
series numbers post-020 implementation - certainly what we were told prior
to the change was that it was merely to simplify the mapping exercise that
it was decided to use distinct number series for former 0171 and 0181
numbers and that the distinction between 'inner' and 'outer' London would
disappear, the two series (and subsequently others) becoming 'common user'
post-translation.

In article , John Shelley
wrote:
What you can say is all esubscribers numbers on an specific
exchange number are within a specified area (excluding out of area
lines of course). The size of the area will vary and the area may
well cover some, or all, of the area covered by another exchange.

This came up in uk.telecom a good while back and someone pointed me
to a site that no longer exists (or I'd quote the URL) which at the
time told me that my home and business numbers, 020 8744 2xxx, are
from Garfield Road, Twickenham. Other 020 8744 numbers go to
Whitton, Hayes and Southall exchanges - the last two are nowhere
near Twickenham. If the site was right 020 8744 50-55 (600 numbers)
go to Whitton, 020 8744 56-59 (just 400 numbers) go to Hayes. Odd?

--
Tony Bryer

"Martin Underwood" wrote in message
...
"John Shelley" wrote in message
news
Martin Underwood wrote:
snip


Yeah, silly question, on reflection! I presume the equipment has to accept
a
fixed number of digits (previously seven, now eight) and identify the
first
four (previously three) as the district and the remaining four as the
subscriber number. If the stream of digits begins with a 0, an alternative
algorithm identifies from the digits that follow how many are the exchange
(eg "20" signifies London, "1344" signifies Bracknell). I can see that if
you only dial the final four digits, they could be confused with 0
signifying "what follows is an exchange" or 1 signifying special numbers
like emergency (112), directory enquiries (118xxx) etc.

Actually the local exchange simply routes all numbers that start with a 0 to
the associated trunk exchange (properly called a DMSU, for Digital Main
Switching Unit).

The DMSU does geographic mapping, routes the call to the relevant DMSU on
the other end which in turn routes it to the relevant local exchange.

If it is a non-geographic number (07*, 08*, 09*) the DMSU routes it to a
special platform that does really clever lookups. That is how a call to a
call centre number at 3am is answerd in India, at 3pm in, say, Sunderland
and at 11pm in the USA.

snip

digit exchange codes are actually located in the same building. Here in
Harrow the exchange building housed both the 8427 and 8863 exchanges and
probably others as well. With the arrival of electronic exchanges the
physical space needed for an exchange was vastly reduced so adding extra
switching capacity within a building that was built to house a
mechanical
exchange isn't a problem. The extra exchange numbers are also needed
for
the non BT operators.

Ah, so new suscribers in an area potentially get a brand new district
number
that's unrelated to that of all the other subscribers in that area? Yes, I
suppose that's one way of solving the problem. Do all subscribers in one
area get one new code and all those in another area get different code:
can
you still say "xxxx [a new code] is Harrow, alongside yyyy [the existing
code]" or is the code-to-location mapping lost?

The association of a single code with a geographic area disappeared decades
ago. Harrow has the 8424, 8427, 8861 and 8863 codes. In the predigital
days I believe these were normally co-located in the same exchange building.

Nowadays the exchange equipment is orders of magnitudes smaller, so in some
case your 'local' exchange is actually located in an exchange building in a
neighbouring area, along with half a dozen other 'local' exchanges.

Your 'phone line will physically be connected to a some sort of device
locally. However this could be a consolidation device that takes all of
those lines on to a neighbouring exchange building. Alternatively it could
just take *some* of those lines to a neighbouring exchange building if there
are logistcal reasons. For example the one room in the building still being
used for exchanges only has room for three and a half sets of lines - don't
forget that at some stage 9,999 lines have to be connected up to each local
exchange.

To answer your specific question, I believe that anyone in Harrow will get
one of the above codes *if one is available*. If not they will get one form
one the exchange in the exchange building where their 'phone line ends up.

regards

Stephen

"Stephen Osborn" wrote in message
...
"Martin Underwood" wrote in message
...
"John Shelley" wrote in message
news
Martin Underwood wrote:

The association of a single code with a geographic area disappeared
decades
ago. Harrow has the 8424, 8427, 8861 and 8863 codes. In the predigital
days I believe these were normally co-located in the same exchange
building.

Well it exists to the extent that there is one or more codes that relate to
a specific geographical area (eg a town or a collection of neighbouring
towns/villages) but don't relate to anywhere else: given a phone code, you
can say which places use it[*]. Maybe the boundaries have become a bit more
blurred and the regions have got larger (like a two-letter code in a car
registration number used to relate to a specific town, whereas now it
relates to a group of counties).


Nowadays the exchange equipment is orders of magnitudes smaller, so in
some
case your 'local' exchange is actually located in an exchange building in
a
neighbouring area, along with half a dozen other 'local' exchanges.

Your 'phone line will physically be connected to a some sort of device
locally. However this could be a consolidation device that takes all of
those lines on to a neighbouring exchange building. Alternatively it
could
just take *some* of those lines to a neighbouring exchange building if
there
are logistcal reasons. For example the one room in the building still
being
used for exchanges only has room for three and a half sets of lines -
don't
forget that at some stage 9,999 lines have to be connected up to each
local
exchange.

To answer your specific question, I believe that anyone in Harrow will
get
one of the above codes *if one is available*. If not they will get one
form
one the exchange in the exchange building where their 'phone line ends up.

What about the situation where the same code is used by several towns and
villages, each of which has a telephone exchange. My code is used by two
moderate-sized towns and many neighbouring villages. I know that my village
has its own exchange (the building is about 100 yards from me right now!).
Presumably some form of supernetting is used: the first one or two digits of
the subscriber's number determine which exchange (consolidation device) the
call is routed to.

[*] I used to work with a guys who was a walking look-up table. He had each
memorised the STD codes and could tell you the code for anywhere or which
places a code relates to (we tested him and he was spot-on every time!). As
if this isn't "sad" enough, he couldn't see that this skill was perceived as
"sad" rather than endearing him to people. He could also see a photo of a
car dashboard instrument (eg a speedometer) and tell you every make/model of
car that it had ever been fitted to.

"Martin Underwood" wrote in message
...

Maybe the boundaries have become a bit more
blurred and the regions have got larger (like a two-letter code in a car
registration number used to relate to a specific town, whereas now it
relates to a group of counties).

Actually, to be pedantic, they still do (to a degree). The first character
is the registration district, the second is the registration office. So, for
example, in a registration such as AA54 ABC: AA indicates Anglia district,
Peterborough office (as would AB to AN). AO to AU are Anglia district,
Norwich office and AV to AY are Anglia district, Ipswich office.

"Ian Jelf" wrote in message
...

The only country where I've ever noticed major differences in number
length is Germany, where they can be very variable, even on the same
exchange.

Is this because they show direct dialling inward with the PBAX as, say,
06857-2456-0 and the extensions as 06857-2456-154?
--
Terry Harper, Web Co-ordinator, The Omnibus Society
75th Anniversary 2004, see http://www.omnibussoc.org/75th.htm
E-mail:
URL: http://www.terry.harper.btinternet.co.uk/

"Jack Taylor" wrote in message
. ..

"Martin Underwood" wrote in message
...

Maybe the boundaries have become a bit more
blurred and the regions have got larger (like a two-letter code in a car
registration number used to relate to a specific town, whereas now it
relates to a group of counties).

Actually, to be pedantic, they still do (to a degree). The first character
is the registration district, the second is the registration office. So,
for
example, in a registration such as AA54 ABC: AA indicates Anglia
district,
Peterborough office (as would AB to AN). AO to AU are Anglia district,
Norwich office and AV to AY are Anglia district, Ipswich office.

But once there would be far more offices, each with its own mark(s): now
they've merged the marks so you cannot tell so accurately where a car was
registered.

I know the situation in Yorkshire better than Anglia: at one time UA, UB, UM
were Leeds, YG was Bradford, CX was Huddersfield and HL was Wakefield. These
were merged so that all these letters signified "somewhere in West
Yorkshire". I think the size of the region covered was further increased
with the new-style AA05 BBB numberplates. I'm not sure why they even
bothered to use new letters: the A123 BCD format had a two-letter location
code (CD) so why not continue to use the same code in the new-style
numberplates? Methinks that they took the opportunity to rationalise (merge)
some of the issuing offices at the same time.

And of course so many cars have personalised numberplates these days that
you often cannot tell anything about a car's age or place of "birth".

I'd better shut up or you'll be thinking that I'm as obsessive as my mate
the walking look-up table ;-) Oh, too late...

"Martin Underwood" wrote in message
...

But once there would be far more offices, each with its own mark(s): now
they've merged the marks so you cannot tell so accurately where a car was
registered.

True. Then again, it had become quite meaningless anyway with large-scale
commercial registrations or with garage chains registering vehicles in their
head office area before shipping them to their salesrooms.

I know the situation in Yorkshire better than Anglia: at one time UA, UB,
UM
were Leeds, YG was Bradford, CX was Huddersfield and HL was Wakefield.
These
were merged so that all these letters signified "somewhere in West
Yorkshire". I think the size of the region covered was further increased
with the new-style AA05 BBB numberplates. I'm not sure why they even
bothered to use new letters: the A123 BCD format had a two-letter location
code (CD) so why not continue to use the same code in the new-style
numberplates? Methinks that they took the opportunity to rationalise
(merge)
some of the issuing offices at the same time.

Yes, Yorkshire is an oddity in the new system, in that the Yorkshire
registration district only covers South and West Yorkshire (YA to YO being
Leeds office and YP to YY being Sheffield office). For some reason East and
North Yorkshire are lumped in with Teesside and Tyneside as the North
registration district, split into three offices (NA to NM at Newcastle, NN
to NT at Stockton and NU to NY at Beverley).

And of course so many cars have personalised numberplates these days that
you often cannot tell anything about a car's age or place of "birth".

Whoever decided that '0' should represent March registrations and '5'
October? What happens if, at some time in the future, they decide to use
every month as a registration month?

I'd better shut up or you'll be thinking that I'm as obsessive as my mate
the walking look-up table ;-) Oh, too late...

I wouldn't dare suggest such a thing! Especially from someone who has the
registrations table saved in a Word document!! ;-))

Have a Happy New Year, Martin.

In article , Richard J.
writes
It wasn't a simple change, as a digit which was part of the exchange
code was moved into the subscriber's number. It was actually the 4th
number change that London has endured.

I think it was actually the fifth, as explained below. I think also
that the current inability of people to format numbers correctly (i.e.
in accordance with ITU recommendation E.123) arises partly from the fact
that the last "change" was actually two transitions about six months
apart.

The first transition was the introduction of the "020" code running in
parallel with the old codes, but with the local numbers staying at seven
digits. During this short period you could call (e.g.) London Transport
enquiries from a telephone in London by dialling any of the following:
"222 1234" or "0171 222 1234" or "0207 222 1234" so that the new area
codes were then genuinely "0207" and "0208".

But then the second transition occurred, with three components: firstly
0171/0181 codes were withdrawn, secondly local numbers changed from
seven digits to eight, and thirdly the "new" area codes changed from
0207 and 0208 to just 020. Thus the LT number became either "7222 1234"
or "020 7222 1234" - the latter form is almost the same as in the
interim period but the position of the space changed. Unfortunately
nobody bothered to explain these three components properly to the
public. In the confusion many people in London started quoting and
dialling the entire national number as they found by trial and error
that this always worked (I guess the increasing use of mobile phones
tended to reinforce this habit).

Hence the continued confusion, or at least lack of concern with putting
the space in the right place when quoting a number.

One notes with surprise that an extraordinary number of shop-fronts and
commercial vehicles appear to have been re-painted in the brief period
during which the area codes were 0207 and 0208, and not to have been
re-painted afterwards. What a pity that nobody told them to wait for
the second number change of the pair. :-)


--
Clive Page