Martin Underwood wrote:
snip
By the way, how much of a London number can you omit? You can omit
the 020 if you're calling from a London number but can you also omit
the district code (the next four digits) if you're calling another
number in the same district?

You have to dial the 8 digits. Think for a moment, how does the equipment
know that the 4 digits entered is a local number and not somebody having a
pause between "dialling" the exchange and the subs number.

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).

In precisely the way you say. Instead of 2 x 10,000,000 numbers there are
now100,000,000. As to the point that it's not exchange codes that are in
short supply. but subscriber numers, all you do is add another exchange
number to an area, creates another 10,000 subscriber numbers. Many of the 4
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.


--
Cheers for now,

John from Harrow, Middx

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"John Shelley" wrote in message
news
Martin Underwood wrote:
snip
By the way, how much of a London number can you omit? You can omit
the 020 if you're calling from a London number but can you also omit
the district code (the next four digits) if you're calling another
number in the same district?

You have to dial the 8 digits. Think for a moment, how does the equipment
know that the 4 digits entered is a local number and not somebody having a
pause between "dialling" the exchange and the subs number.

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.

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).

In precisely the way you say. Instead of 2 x 10,000,000 numbers there are
now100,000,000. As to the point that it's not exchange codes that are in
short supply. but subscriber numers, all you do is add another exchange
number to an area, creates another 10,000 subscriber numbers. Many of the
4
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?

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

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 code to location mapping is, I believe, becoming blurred. My BT phone
is 020 8863 xxxx, and my NTL phone line 020 8357 xxxx. How big an area the
NTL 8357 covers I don't know, and my BT knowledge is now rusty, 12 years out
of it. 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 is definately a possible, maybe
situation.


--
Cheers for now,

John from Harrow, Middx

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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

On Fri, 31 Dec 2004 15:11:59 GMT, "John Shelley"
wrote:

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

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 code to location mapping is, I believe, becoming blurred. My BT phone
is 020 8863 xxxx, and my NTL phone line 020 8357 xxxx.

This is indeed the case. I used to work in Intelligent Networks,
setting up number translation services for large national companies
who would want all callers to be routed to their nearest local office.
Firstly, they would invariably give us their requirements in terms of
postcodes, which would necessitate a long explanation to the account
manager of how postcodes were a system used by the Royal Mail to
distribute letters and parcels, and there wasn't a one-to-one mapping
to STD codes, and secondly, it was usually impossible to meet their
requirements when it came to non-BT numbers, as cable companies seemed
to assign their Manchester (for example) 1000-number blocks to cover
the entire city, in the order customers were signed up...

Charlie

--
Remove NO-SPOO-PLEASE from my email address to reply
Please send no unsolicited email or foodstuffs

"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.

"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.