BT Basics - by Pharlin J. Hack

OK, this article is to supplement the lack of basic information that seems hard to find for people wanting information about the UK fone system. It is by no means comprehensive or detailed but more a starting off guide that deals with some of the more interesting things that anybody can go off and experiment with. Everything is as and please read the credits at the end of the phile. This is full of information that is meant for educational use only, if you somehow manage to work out a way to defraud BT from it then it has nothing to do with me, blah blah blah. Please enjoy.

OK so where do we start?

If you can't be bothered reading the whole whack you can just skip to

[Image] payphones [Image] chargecards [Image] blue boxing [Image] Nostar

codes [Image] resources

Some basics, in the UK most people are fed by the monopoly giant, British Telecom, (BT from here on in) and while there are others (mainly Mercury, and now United Artists), BT seem to have the hold, indeed Mercury have to rent the lines off of BT in the first place. Come September of 95 however, AT&T are arriving and Mercury and BT are crapping their proverbial pants. In fact a lot of the technology that BT employs is just 'borrowed' American technology from BOC's e.g. some of our digital Xs are based on 5ESS, our caller ID is just CLASS technology modified and applied here.

For the financial year of 1994 BT made a pre-tax profit of 2 3/4 billion pounds and have sacked over 90 000 employees in the past 4 years. The largest profit margin ever recorded was for the 1991 financial year when BT made a pre-tax profit of over 3 billion pounds.

There are three kinds of exchanges (OK, smarty pants there are more, but three 'types') and these can be categorised as digital (sysX, sysY), semi-electronic and electro-mechanical. Around 75% of customers were connected to digital exchanges in 1994 (around 26 million exchange lines) and BT reckon by 1996 all customers will be served by digital or electronic switches. All international calls are handled by 4 dedicated exchanges. The digital exchanges, system X and system Y along with the TXE4 exchange are connected together using CCITT C7 signalling and provide the method for call tracing and CLID.

Houses with fones in the UK are fed by two cables that come from the exchange via telephone poles and underground. The two cables (line pair called A and B) connect to a junction box somewhere in your house to which your fone plugs into. Normally, line A runs at -50V and line B at 0V, don't worry about connecting A and B incorrectly because it shouldn't make too much difference. Little bit of history here, because of wiring changes and depending on how old your house is you may have different wiring. The defacto now is the familiar Blue/White, Orange/White and Green/White (with reverse, i.e. White/Blue etc. etc.) but before that was a mass of wires including orange, brown, green, white, blue, the list goes on....anyway things get even more complicated when you strip a BT fone down and find red, green, white and blue wires. sheeesh. You'll be pleased to know that we are only interested in 2 of these wires, basically the A and B wires that we talked of earlier. Here is how they compare;

                   Line A                  Line B
                   ======                  ======

          Old  ->  orange                  light blue
          New  ->  white/blue stripes      blue/white stripes
          fone ->  white                   red

Lost? just remember that the two lines (A+B) can be reversed and it shouldn't make that much difference, the table above gives you an idea what to do with the mass of cables that you have depending on where you are, i.e. if you are playing with your beige box. There is a third wire needed for the bell (or shunt) but that is not needed at this stage... but is the orange/white wire in the newer wiring system (the green/white, white/green do nothing and the white/orange wire is needed in PABX systems ). If anybody wants specific wiring plans and schematics then get me on IRC and I'll pass some on.

Now, go find those interesting big green boxes (open them with a hex wrench) beside the road, shimmy up the poles, find the junction boxes in your work, college, schools and experiment with your new found friends. You don't need told what uses you can have with them.... just get a beige box and experiment. Just remember that A connects to A and B to B.

right, that should cover wiring, now onto


In 1994, there were over 120 000 public payfones dotted around the country and BT spent a whopping 10 million GBP on the physical security of their payfones (and still managed to screw up). BT payfones can be split into two main types; the payfones where cash has to be inserted and cardfones where disposable bought cards have units on them that are used up, there are now variations on that theme with payfones now accepting credit cards and the new "Payphone 2000" which accepts cash, credit cards, charge cards (more on these later) and fone cards. What you must remember is that payfones are for all intents and purposes just regular fones that need a unit of some sort to be deposited before a call can be made.

Now for the 10 million that BT managed to spend you'd think that they'd get their money's worth but in fact that 'physical security' can be defeated in around 5 seconds with a screwdriver and a pair of pliers. For those who are inclined toward committing vandalism of the physical kind this one is for you;

1: insert the screwdriver into the coin
     return slot at the bottom and lever it
     so that the bottom will pop out           | 789    ____ |
                                               | *0#    |   ||
                                               |        |   || < coin return
                                               |        --|--|   slot
                                               ---------- |---
                                            screwdriver>  O

   2: now the coin return slot should be   |    |
      like this (side view)                |____o\

   3: the o in that diagram represents a round bit of metal. remove it
      with brute force and the pliers

   4: Now you are ready to make free fone calls. put a 20 pence piece in
      the machine

   5: now put your fingers up the coin return slot (two fingers is best)

   6: Wiggle your fingers around and the 20p should fall into your hands,
      but still register

   7: the max. is 1:60, but this can be supplemented when it goes down

   8: when leaving, it is sensible to push the slot back in (easy removable
      by hand again) so that it goes unnoticed

like I mentioned, this won't work on the newer pay fones or COCOT's, just the traditional payfones.

As stated before a payfone is just a fone connected to a standard line. The weird things about payfones (these don't cause too many problems - just slight nuances) is that the mouth piece on the fone is disabled until your call is connected. However a friend of mine who works in exchanges at BT reckons these can be switched off with some RF gear. Disabling the mouthpiece means no tones can be sent down the fone until the call has been connected. One of the reasons for this stems back to a time when BT offered "remote control" answering machines whereby you where supplied with a white box and you could dial home and by adding the digits 00 or 99 the call went through uncharged (because it was routed as an emergency call), people sussed out that if it worked for their home calls then it would work for other numbers too.

Another thing that is annoying is the fact that you can not DTMF dial on a payfone line until the call is connected (this isn't strictly true... in some areas DTMF is allowed but that is more the exception) and that is a characteristic of the line, not the fone. The fone itself is more than able to supply the DTMF tones; to switch the fone to DTMF press the * when your call is connected. The final annoying thing about payfones is that for the first minute of an incoming call or an outgoing call to an operator an annoying bee boop (or cuckoo tone) is generated by the fone.

The reason for this is to 'wake' up the operator, that is, if you try making a reverse charge call (call collect) to a payfone, when the handset is picked up the operator hears the cuckoo and knows not to connect the call. However, if you disconnect or by pass the cuckoo (there is a way) and are lucky not to have an alert operator (see later) the operator will connect the call. Now originally I thought that the cuckoo tone was the only thing that would distinguish a payfone from a regular fone but this is not strictly true. In the US for example the operators have a database of which numbers don't accept collect calls (202 456 1414 for example) and payfones are included in this lot, in the UK however a thing like that doesn't exist.

On digital exchanges (sysX only in this case - I think) though, flags can be assigned to determine what type of line the caller is on, i.e. business, customer, payfone, cardfone. This means that even if you have the cuckoo tone disabled and the operator is particularly observant then she will know not to connect the call (provided you are served by a digital exchange) - however this has only happened to me once. That is, an operator connected a collect call and then a few minutes later came back on the line and told us what she'd done and disconnected us. What I am trying to say is that an operator knows whether you are calling her from a payfone or not but this can be reduced significantly by removing the cuckoo (HINT: it is generated by the fone, not the line - hook up a beige to the payfone feed and that sorts it)

Now, some of you might have already clicked onto something but for the slower children in the class - have a think about this. The cuckoo tone lets a BT operator know that the fone does not accept collect calls. An American, French, Canadian operator hasn't a clue what the hell the cuckoo tone is and will quite happily let the call go through collect, in the same way the international operator (155) will quite happily connect a reverse charge call to an American payfone... it is surprising how many people have not thought of this (or maybe it is because I am hanging out with the wrong crowd). There was a time when you could call AT&T direct (0800 890 011) and ask to make a collect call to a payfone in the UK and the call would be connected but alas, times are a changing.

Now a quick note about COCOT's that appear around the place. The typical newer ones are white square boxes with grey borders and are made by BT. These can be found in pubs, cinemas and on private property and are basically installed on residential or business lines. A lot of these (if installed by the owner and not BT) are not set-up properly, that is the flags aren't set-up i.e. the operator hasn't the flag to tell her whether it is a payfone or not, it will just come up as a residential or business number. Many of these payfones do not mute the handset, or disallow DTMF (there have even been reports that there is no cuckoo - but I have never come across it before). However, these are more fun to play with.

I forgot to mention, if you want an ANI from a payfone, just insert a credit (don't worry you get it back) and dial either 174 or 175 - wait - the exchange will read out your number and then call you back, however most of the payfones that you come across will have the number printed anyway.

I think that that is all I can think of to say about Payfones at the moment, another thing to point out is that if you fone the operator and claim that you lost money through a call, she will credit the amount that you lost to your home fone bill (or any number that you give them), but I don't really think that "I put in a five pound note" will really cut ice :)


These little babies are a beauty thanks to BT and their great thinking. In 1994, there were more than 3 million chargecards in use and they could be used from over 120 countries around the world. What they allow you to do is to call a number (144 in the UK) and enter in your card details, which consists of a 10 digit card number and a 4 digit PIN, then you enter the number that you want to dial.

BT charge cards come in 3 different flavours, home, national and international. Home allows you to only call your home fone number (in which case the last 4 digits of the card number is the PIN), national which as the name suggests allows only national calls and international, well you get the idea.

If you follow the computer prompts all goes well, enter your card number, your PIN, fone number and your call is connected at 15% cheaper than a regular payfone call. However, thanks to BT's greed, if you fone the operator there is a surcharge of around 1.53 GBP BUT she will connect the call without even asking for your PIN, that's right get the card number from somebody (go on, practice some SE skills) fone the operator and ask to make a chargecard call, give the number you want to call, the card number and away you go. In fact for international calls, you do the same but you use a different number (it's on the bottom of the card). - BT wake up - A point to note is that on the cardholders bill, all chargecard bills are shown and the number dialled and the number dialled from are clearly shown, so don't do this from home kids...

Blue Boxing - The Facts

Ahh, in the beginning, there was the 2280Hz tone - this was the UK equivalent of the magic 2600Hz tone and was used in the same way with a separate bunch of MF tones, now alas the only place that you can use that lot with is in hicksville when you are on a non digital exchange and even then there are nasty filters blocking the magic tone soooo.....you start to look elsewhere.

Now, we have what is called 0800 numbers which are the UK equivalent of 1-800 numbers and some of them (especially ones starting 0800 89 XXXX) lead you overseas to new and exciting lands which means new and exciting fone systems. Here are some listed below, go hunting for others;

0800 890 016 - Canada direct 
0800 890 027 - South Africa direct
0800 890 031 - Netherlands direct 
0800 890 032 - Belgium direct
0800 890 033 - France direct 
0800 890 034 - Spain direct
0800 890 036 - Hungary direct 
0800 890 038 - Yugoslavia direct
0800 890 039 - Italy direct 
0800 890 042 - Czechoslovakia direct
0800 890 043 - Austria direct 
0800 890 045 - Denmark direct
0800 890 046 - Sweden direct 
0800 890 047 - Norway direct
0800 890 049 - Germany direct 
0800 890 055 - Brazil direct
0800 890 056 - Chile direct 
0800 890 061 - Australia direct
0800 890 064 - New Zealand direct 
0800 890 065 - Singapore direct
0800 890 066 - Thailand direct 
0800 890 081 - Japan direct
0800 890 082 - Korea direct 
0800 890 123 - Bermuda direct
0800 890 212 - Morocco direct 
0800 890 852 - Hong Kong direct

Right, sift through those (no I'm not telling you which ones) and find one that is a CCITT5 line (nice beep when they answer) and grab a copy of Bluebeep (courtesy of Mr. Dittmeyer) and do the following...

  1. dial your 0800 number (It must be a CCITT5 line)
  2. send down 2600/2400Hz together, then 2400Hz on it's own. The length of the tones and the delay between them varies with different lines, experiment boy.
  3. dial the number you are calling as follows... KP2-CountryCode-AreaCode-Number-ST (you can't use KP on country direct lines, but you can on others)
  4. as if by magic....

(There is an excellent article on blue boxing in the 20th century in CoTNO 4 which goes into this whole topic much clearer and better than I do - go check it out.)

Note, don't give up if it doesn't work, you have to experiment and play around, all things come to those who work....now despite what anybody tells you this works, BT have just removed one global route as I type this, so get going and find others.

Norstar PBX's

The following are the default codes for the Norstar PABX provided by BT.

They are becoming more and more popular around the country and are popping up all over the place. (try new dept. stores, GAP have just bought a whole load for some of their stores and ODEON cinema's [the newer ones] all run on them) - an easy way to spot the fones that run on Norstar's net is that they have a nice big speaker along the top and have a little LCD screen which displays instructions and at the bottom of the 1-9 dial pad there is a volume bar. The four models in the family are the M7324, M7310, M7208, M7100 but the latter can't be programmed. hunt them out and enjoy.

To enter the config set-up do the following;

  1. press the key on the fone
  2. key in **266344
  3. prompted for password, key in **266344
  4. you are then prompted through different settings using the little screen, these are; Line data, Line Access, Call Handling, Change Extensions.

To enter the admin features, key in;

  1. the key
  2. **23646
  3. prompted for password, key in **23646
  4. this feeds you through all sorts of admin features, speed dialling, removing restrictions, permissions, clearing lines, call barring, overriding, changing passwords.

You would be surprised how many offices, stores and business are now operating on Norstar's network, again if you want any specific information regarding these, feel free to get in contact with me or call the Norstar help line on 0800 378 822.

That's all I really have to say for the moment. I just wanted to put out some information for those people who know lots about the American fone system but who live in the UK and are frustrated. If anybody want some specifics then get in touch.

References and Credits

(recommended reading)

uk.telecom FAQ 1/2/3 compiled by James R Grinter (the phone man)
wiring schematics written by Alan J Flavell
Screwdriver and Pliers images by Cucumber at UAT
Big thanks to Noakes for putting me straight on boxing facts
Pete at Mercury
Phil at BT exchanges
British Telecom
Onkel Dittmeyer for coding Bluebeep


ftp.pipex.net /pub/telecom

All information is as and was correct at time of writing. Written and compiled by Pharlin J. Hack, take care, wipe feet, clean teeth. enough. I'll see you at Access all Areas.