Phone numbers

Why do we need another digit in the phone numbers ?

[left in for historical interest and 'told you so's ;-)]

The existing numbering scheme is mixed 8, 9, and 10 digits (in all cases including the initial "0" - which isn't really part of the number. Theoretically, the maximum number of numbers is 900 million, excluding 00XX codes because by CCITT [now ITU] convention you can't have the same digit as the first digit of the NDC (National Destination Code, that's the STD code without the "0") as you have as national trunk prefix. 01XX has been cleared (solely to make the code change possible) and this reduces the total number of possible numbers to 800 million. Where the numbers are used for geographic areas, and users are offered the option to dial those numbers without a trunk code, then 201,000 numbers in each group of 1,000,000 become unusable. But other number ranges, such as cellnet, freefone, paging services and premium rate numbers are not limited in this way. So the real "supply" of numbers in the UK is about 650 million. Experience shows that allowing for the continuing process of number changing, and the fact that there will always be some numbers that cannot be allocated, about 60% of the supply can be utilised at any one time. This means that the present scheme restricts us to using no more than 400 million numbers at any one time. In fact the UK (plus the Channel Islands and the Isle of Man) is currently using less than 30 million numbers, which should allow plenty of room for growth.

So why is there a problem? Because the numbering ranges are tied to fixed locations by a formula that has no place in modern telecommunications, and which was originally introduced solely to enable fairly primitive mechanical equipment to route and charge calls correctly. As a result there is a serious imbalance in the distribution of numbers: one code, such as 0393, has only 25 numbers in use - while another, such as 0532, has over 300,000.

The proposed extra digit will NOT solve the problem. Agreed it will create a lot more codes: but even now there are 56 codes that have no numbers on them, and that figure (surprisingly enough) is increasing, not decreasing !

But the extra digit won't provide any more numbers within each of those geographic areas served by individual codes, and that is where the brunt of the demand will be. Currently, growth is caused both by the need for more lines (particularly for fax) and by new operators taking blocks of numbers within the individual areas. Future demand will be driven by existing services such as DDI (Direct Dialling In to PABXs) which is a heavy consumer of numbers, and by new services such as Teenline, and Distinctive Ringing.

The latent demand for DDI has been suppressed in the UK by both the lack of availability of connections, and by high tariffs imposed by BT. The arrival of DASS2 (the ISDN signalling system for digital PABXs) makes availability considerably easier, and Mercury and BT are now offering DDI at a much lower tariff.

As demand grows, the larger cities will overflow their allocations of numbers and further complete changes will become necessary. It has recently been announced that five of those cities (Nottingham, Leeds, Sheffield, Leicester and Bristol) are to change to seven digit schemes in 1995: and looking at the list of codes vs numbering density in each (now, I believe, in the uk.telecom archives) it is clear that further places, including Brighton, Belfast and Bournemouth, are also likely to run out of numbers in the next few years.

London's 071 was not expected to last beyond 2005 at the previous growth rates; however allowing for the greater demand caused by DDI and new services, the 071 number range is likely to be exhausted by the end of this decade. At that stage the two options will be either to split the 071 area into two codes, or to convert all of London to an eight digit scheme. This is not a new phenomenon ... even before London split into 071 and 081, two other capital cities (Paris and Copenhagen) had each tried an identical scheme. Those schemes failed, mainly because of confusion between "inner" and "outer" zone numbers, and each was superceded by an eight digit scheme which is reported to have been very successful.

So we don't need an extra digit. And the extra digit (if we get it) won't solve any problems. We do need a complete overhaul of the numbering system, whether we have the extra digit or not. As that overhaul will have to come, it would be far better if we waited - and planned a single change that would solve all the problems, rather than have a hotchpotch of further changes.

But - while the extra digit won't achieve anything for the customers, it will have an interesting effect on BT's sales figures. As soon as the extra digit is imposed, all Mercury Smart Boxes, SmartSockets, and compatible PABX and key systems will stop working unless they have been modified (at the user's expense) because they will be unable to recognise the longer codes. With the reduced differentials between Mercury's tariffs and BT's "options", some users may find it uneconomical to pay the charge for the modifications.

Similarly, payphones supplied before 1992 by BT's competitors will be unable to charge correctly for calls. Some will have to be modified, at a cost, while others, that cannot be modified, will have to be scrapped. Some of those payphones are still on sale to unsuspecting members of the public without any warnings being given as to what is in store.

So who decided, and what were the choices?

Ovum Ltd, 1 Mortimer St, London W1., a respected and independent telecommunications/management consultancy, carried out the investigation for OFTEL. They were asked to study the first five options below.

'Numbering for Telephony Services into the 21st Century

A Consultative Document' July 1989 Oftel. Sample quotes

There are many possible options for a future scheme.. This document identifies 5 practicable options which span the range of possibilities.

The starting point for any new plan is the current scheme. This is essentially a nine digit plan. (The leading zero dialled for trunk calls is a prefix which is not strictly part of the full telephone number.) [<== here comes the selective blindness]

Who owns this numbering space ?

The numbering space is owned by the nation, and (technically) Oftel is its custodian. But in practise Oftel delegates the majority of decisions to BT, and takes advice from BT (and sometimes other operators) on major issues. If Oftel owned the numbering space and managed it effectively, Mercury would have been allocated 0800 and 0345 numbers to issue to their customers, rather than having to use new codes (0500 and 0645) which are still not recognised by some BT (and private) payphones.

I've heard someone mention about Mercury's 0500 service, what is it ?

This is Mercury's 'freecall' service introduced at the end of 1992 and is their equivalent of BT's 0800 service. Similarly Mercury 0645 service, called 'localcall' is the equivalent of BT's 0345 (now tackily 'Lo-call') service. 0800 89 prefixes normally indicate that the number is connected to a location outside the UK: overseas telephone companies 'country direct' services. Some 0500 89 prefixes are also like this, but mostly those mirroring 0800 numbers.

How can I phone American 1-800 (toll free) numbers from the UK ?

Latest information is that now you can ring a 1-800 number from any BT line, albeit with the normal international charge being levied.

 American 1-888 codes do not yet appear to be covered by this.

[I forget where this information came from, but someone has tried it recently, and not had any luck.] For a list of U.S. companies with U.K. 0800 numbers, call AT&T Direct (see another answer) and ask for 816-654-6688 collect. Then ask the person who answers for extension 7642 (if you're US military, then apparently you should ask for extension 9661 instead). You should call during US business hours.

How do I dial a number with a mnemonic in it ?

Here's a letter to number mapping; this is potentially useful because many 1-800 numbers have mnemonics in them.

        Num     UK      USA         1       2       3
        1                          ABC     ---     ---
        2       ABC     ABC        DEF     ABC     ABC
        3       DEF     DEF        GHI     DEF     DEF
        4       GHI     GHI        JKL     GHI     GHI
        5       JKL     JKL        MNO     JKL     JKL
        6       MN      MNO        PQR     MNO     MN
        7       PRS     PRS        STU     PQRS    PRS
        8       TUV     TUV        VWX     TUV     TUV
        9       WXY     WXY        YZ      WXYZ    WXY
        0       OQ      Operator   Oper/+  +       OQZ

There is no 'Z' in either system, and there's no 'Q' in the States.

The other three columns are

 1. Mitsubishi MT-9, Motorola MR1
 2. Motorola 7500, Roamer 300, 500
 3. Nokia GSM2010, Orange.

What are BT Phonebase/ Electronic Yellow Pages/ TeleDirectory and how do you get access to them?

BT Phonebase allows you to use your modem for directory enquiries. You get access to the whole country by name, street, town, even by phonetic partial match. You get access to up-to-date information, not a phone book that's maybe a year old. It gives you name, full address including postcode, and phone number. Phonebase is a seperate system, though it is supposed to be regularly updated from NIS - the DQ (Directory Enquiries) system.

It costs nothing to join (phone 0800 919 199 or fax (0114) 244 0157 and they send out the form).

The modem call is charged at long distance rates [ BTs 'n' rate is about 15 p/minute but Mercury (business tariff at least) charge about 9 p/minute], and is only 2400 baud. But even so, you can look up numbers for a fraction the cost of Directory Enquiry calls (37.8p +VAT).

As for the retrieval system, well, it was written by a bunch of Americans and BT thought it was perfectly adequate. There was a front-end access program available, written by BT, though they have now discontinued support and are planning to change the interface. The program is available from <URL:>, and someone is trying to obtain the source and details of the proposed new interface definition.

BT also recently launched an online directory enquiry system for personal computer users. Called TeleDirectory, the system is 'aimed at customers who require five or more telephone numbers a day' and costs 12p per enquiry. It's based upon an MS Windows front end, and comes with a software at a cost of UKP300 per annum, with discounts on 5 licenses or more. Ring 0800 200 700 for further information.

Electronic Yellow Pages is quite obviously named. It offers access from (01734) 505533 (vt100) or 505522 (Videotex). Helpline on (01734) 506506, for more info. Access via a Reverse Charge X25 call is no longer available. You can now access EYP via a web interface at <URL:>. {*}

How can I get UK phone directories on CDROM?

BT offer 'Phone Disc', basically BT's Phone books on CDROM. There are three options available - The annual Phone Disc, updated annually, is available at 199 UKP, Phone Disc updated quarterly costs 1,600 UKP and the Network Phone Disc, for very high volume users with multi-server applications, costs 3,000 UKP per annum. Contact 0800 526 281 free for further information.

There is currently no other offering that has residential numbers included, though there has been mention of a disc including business numbers. Hurdles to a CDROM including the UK phone directories include BT's assertion of copyright over the collection (see also regular discussions in uk.telecom).

What defines a local call area?

The boundaries are all quite complex. The only reference seems to be your local phone book, which will tell you where you can call for local costs. The complete list is available from BT on floppy, but costs a fortune!

From BT's 1994 price update (Item Code 964780 (2/94)), it says

"Telephone exchanges are grouped together into charge groups to determine call charges for local and national calls. Each charge group has a "charge point". A call made within a charge group is usually a local call. Charges for other calls are generally based on the distance (up to or over 35 miles) between the charge points in the originating and called charge groups."

When did the National Code Change take place?

The National Code Change took place at 1am on 'Phoneday' (16 April 1995). The new codes and numbers were available for use since 1 August 1994. Phoneday is when the old codes and numbers were withdrawn. Call 0800 010101 (BT) or 0500 04 1995 (Mercury) for more information.

See other regular posts, and information supplied by your telephone provider for details of number changes.

When did the International access code change happen?

At the same time as Phoneday, the dialling code for making an international call changed from 010 to 00.

I want a new line with a particular number, or want to renumber an existing line to a particular number.

You can (generally) do this as long as the number is not allocated or reserved for somebody else. You will be told that the number you want is not on their list, but ask them to call the number allocation people for your area and get it for you.

It CAN be done. NOTE: If you are requesting a new line tell them before they start tapping your details that you want to choose a number.

What sort of dialling code is <x>?

(0990 was used for Ascot, Chobham, and Wentworth, until a few years ago. Ascot moved to 0344 (2, 87) Wentworth to 0344 (84) and Chobham to 0276 (85))

[note: not all of these are in even BT's phone book]

 01399  VodaPage Network        local {*}
 014260 ?                       Free
 014261                         Free
 014262                         local
 014263                         ff1
 014264                         regional
 014265                         regional
 014266                         ff1
 014267                         Free
 014268                         local 
 014269                         regional
 014591  ?                      regional
 014592                         regional
 014593                         Free
 014594                         regional
 014595                         regional
 014596                         Free
 014598                         regional
 014599                         Free

 0331  Vodata premium rate     p1
 0336  Vodata premium rate     p1 {*}
 0338  Mercury premium rate    p1 {*}
 0345  BT LoCall               local
 0374  VodaFone                M
 03745                         b
 0378  VodaFone                M
 0385  VodaFone (GSM)          M {*}
 03856 Vodata services         b {*}
 0402  Cellnet Mobile          M {*}
 0408  BT Mobile               e     (Personal Assistant) {*}
 0421  VodaFone                M
 04211                         b
 04560 Orange                  m {*}
 04561 Orange                  m {*}
 0468  Vodafone (GSM)          M {*}
 0500  Mercury                 Free
 05415 ?                       b
 0585  Cellnet                 M
 0589  VodaFone                M
 0640  MCL                     p0 UKP1.50/minute
 0645  Mercury                 L
 0660  Mercury premium rate    p1 {*}
 06966 ?                       p1
 07010 Flextel Personal Numbers d {*}
 07017 Flextel Personal Numbers d {*}
 0800  BT FreeCall             Free
 0802  Cellnet GSM             M {*}
 0831  VodaFone                M
 0836  VodaFone                M
 08360 VodaFone services       b {*}
 08361 VodaFone services       b {*}
 08364 VodaFone premium        p1 {*}
 08368 VodaFone Services (vmail)  b {*}
 08369 VodaFone Services (pabx)   b {*}
 0839  Mercury premium         p1 {*}
 0850  Cellnet                 M
 0860  Cellnet                 M
 0881  Mercury premium         M {*} [or should that be p1?]
 0891  BT                      p1
 0894  BT                      s0 35p flat rate
 0897  BT                      p0 UKP1.50/minute
 0898  BT Premium Rate         p1
 0910  BT services               {*}
 091021 ?                      n
 09411 Hutchison Paging        regional
 0956  Mercury One2One         d
 09567 Flextel classic         d {*}
 0958  Mercury One2One         d {*}
 09580 Mercury One2One Freecall Free {*}
 09581 Mercury One2One Localcall local {*}
 0973  Orange PCS              d
 0976  Orange PCS              d
 09797 Jersey Telecom GMS      h {*}
 0990  BT                      b  derived services
 09911 MCL                     p0
 09919 MCL                     p0

 ff1  - fixed fee, regardless of duration
 h    - calls to 'new services'
 m, d - mobile phones. 
 n    - information services
 p0, p1, s0 - premium rate services [watch out for p0!]

What codes are free to the caller?

1471 is currently free of charge. 141, 1474 and 1470 are chargeable at the same rate as the call being made - there is no charge for using the 1xx(x) code. The following codes are also free to the caller,

(except see note below)

 112   = European standard Emergency number 
 131   = Mercury PIN access
 132   = Mercury CLI access
 133   = Mercury calling card (0500 800800)
 139   = Mercury Extended Ingress, currently on test
 144   = BT Chargecard
 145   = BT "Fixed Mobile Convergence"
 150   = BT Residential Customer Services
 151   = BT Residential fault reports
 152   = BT Business Customer Services
 154   = BT Business fault reports
 1571  = Message Retrieval
 1601  = ACC Indirect Access
 1602  = ACC Indirect Access
 1611  = Energis Indirect Access
 1616  = Energis Indirect Access (actually their contact line)
 1620  = Energis direct (CLI) access - includes the initial "0"
 1621  = Energis direct (CLI) access - includes the initial "1"
 1660  = Worldcom Access
 17070 = (replacement for 174/175) {(}
 17094 = Network Based Call Answering Service - Diversion on busy
 17095 = NBCAS - Ring Tone no reply
 17099 = Alternative emergency code
 174   = Faultsman's ring back 
 175   = SALT test
 176   = Customer Pair Localisation Equipment 
 177   = Customer Pair Identification (reads back number)
 195   = Blind customer DQ
 153   = International DQ (see note)
 155   = International Operator
 190   = Telemessage
 192   = UK DQ (see note)
 198   = Operator (used for revertive calls)

Remembering that these are the codes that BT systems recognise, beacuse that related to the original question. Other networks will recognise other codes, and may not recognise all of these. Oftel are working on a list of standard codes, and may require some of these to be withdrawn when they do not conform to the standard. This is especially likely to apply to 3-digit codes, as the standard will become 4-digit 1XXX codes, with exceptions such as 100, 112 etc.

123 is a local call from anywhere (the old numbers for Timeline, ending in 8081, were usually but NOT ALWAYS a local call!)

153 and 192 are chargeable at the rate for a call to Directory Enquiries. 100, 155, 190 and 198 route to a BT operator: the call to the operator is free, but any call connected by the operator will usually be chargeable.

How should I correctly write my telephone number?

[quote: "The following is information sent by OFTEL, originally written by BT. I have tried to reproduce it letter for letter, but the BT text was right justified and mine isn't! E&OE. Adrian Kennard. Jan95"]


The recommended style of presentation of new telephone numbers is based on customer reseach. Brackets are used to identify the national code - which is omitted when dialling within the same area. The use of hyphens is no longer recommended.

Metropolitan Areas (ie those with 7 digit local numbers)

These should be in the "All Figure Format" with the local number

shown as 3+4 digits eg

          Tel: (0171) 239 1482
               (0117) 927 2272

Non-Metropolitan Areas

The Local number is shown without any space;

          Tel: (01273) 568010
               (0781 39) 9587

If customers wish to include the Exchange name it should be shown

before the National Dialling Code eg

          Tel: Brighton (01273) 568010
          Tel: Barlaston (0781 39) 9587
          Tel: Bristol (0117) 927 2272

NON GEOGRAPHIC CODES (Mobiles, Paging, Linkline etc) In all cases it is necessary to dial the full national number. In these cases brackets are not used.

          eg  0800 526174,  0891 234876


The international convention is to show the country code (for the UK = 44) and number prefixed by "+". The "+" indicates that callers should dial the appropriate International access code according the country from which they are calling. International calls omit the inland prefix "0" thus the Brighton example would be shown as

    International  +44 1273 586010

Together these would be shown as

               Telephone:Brighton (01273) 586010
                 International: +44 1273  586010

NB For Fax lines the same conventions apply but using "fax" in place of "Tel".

What is a "DE block"?

The digits of a national code or phone number are referred to by letters according to where they are in the number. After the initial zero (which of course is NOT part of the nationally significant number) the digits are given successive letters in sequence - but excluding the initial "1" if it is present.

For example, in 0171 634 8961, letters are allocated as follows AB CDE FGH

 In the case of the Reading numbers 
 such as 0734 413131, the letters are allocated in the same way:
          ABC DEFGH

so that (in that case) the DE digits are the first two after either the 0734 or 01734, as appropriate. In the days before digital switches, this was the point at which BT (in nearly all cases) did its final route selection to the exchange or UAX serving the required number range. The significance today is that the Oftel numbering unit

only allocates numbers to licensed operators in blocks of 10,000 i.e. all the numbers with the same DE digits are allocated to the same licensed operator. When you run out of DE digits for a particular area (i.e. national destination code), you have de facto run out of numbers!

It was originally suggested to Oftel that numbers should instead be allocated in multiple blocks of 1000, as this would provide greater flexibility. Sadly they did not adopt this suggestion: if they had done so, Reading might not be in the predicament it is in today.

Version: 2.10 Last-modified: Time-stamp: <96/05/12 23:04:20 jrg>