231 lines
9.8 KiB
Plaintext
231 lines
9.8 KiB
Plaintext
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
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³ Founded By: ³ º Network Information Access º ³ Mother Earth BBS ³
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³ Guardian Of Time ³Äº 04JUN90 ºÄ³ NUP:> DECnet ³
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³ Judge Dredd ³ º Judge Dredd º ³Text File Archives³
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ÀÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÙ º File 33 º ÀÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÙ
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³ ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ ³
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³ ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» ³
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ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄĺ UK Telephone System ÇÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
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ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
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Telephone services in the UK are provided by the following
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organizations:
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British Telecom
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Mercury Communications
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Hull Telephone Company
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Vodaphone
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Cellnet
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For historical reasons, BT allocates area codes. This will change in a
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couple year's time.
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The bottom level of the BT system is the "Junction Exchange" (JX in
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this document). A JX is a unit which handles 10,000 subscriber
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numbers, numbered 0000 to 9999. A number may have several lines
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attached to it (hundreds in some cases). These four digit numbers are
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called LNs (Line Numbers) in this document.
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In a few rural areas, some subscriber numbers are three digits. The
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appropriate JX thus takes some LNs as being three digits, and some
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(possibly none) as four. Such JXs are being phased out. [This should
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be distinguished from the case where all LNs in a group of ten go to
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the same subscriber, and are interconnected. For example, Basildon
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hospital officially has the LN 2811. In fact, all of LNs 2800-2899 go
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to the hospital switchboard, and the JX will route the call as soon as
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it sees "28".]
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JXs are grouped into "Area Codes" (AC). Each JX has a one or two digit
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number within its AC - one digit numbers are being phased out. The
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exception is in "all-figure areas", where each JX has a three digit
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number. These numbers do not begin with 0 or 1.
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Each area code has a number. For most area codes, this is three
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digits, but for all-figure areas, it is two digits.
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The "number-space" for area codes is used as follows. All normal area
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codes begin with a digit from 2-9. The area codes for the all-figure
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areas are:
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Birmingham 21
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Edinburgh 31
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Glasgow 41
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Liverpool 51
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Manchester 61
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London inner 71 (new)
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London outer 81 (new)
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Tyne & Wear 91
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Of the 720 three-digit codes, about 600-650 are in use (I do have a
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complete table in numerical order, but it's not in machine-readable
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form). Certain codes have special meanings:
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345 Calls charged at L rate irrespective of distance
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482 Hull Telephone Company
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800 Free calls
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831 Vodaphone
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836 Vodaphone
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839 Calls charged at m rate irrespective of distance
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860 Cellnet
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898 Calls charged at m rate irrespective of distance
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Mercury has been allocated fifteen JXs in the 71 AC and the same
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fifteen in the 81 AC. I believe that all Mercury subscribers have
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numbers in this AC, irrespective of location.
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Area code 1 was used for London (both inner and outer) until 0001 on 6th May
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1990; I am unaware of any plans for it. Area code 10 is obscured by the
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international access code. No area codes begin with 0 (but see below).
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From any BT subscriber, you can call any number by:
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0 + area code + JX number + line number
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For example, anyone can call me by 0-954-78-0223. In addition, there are
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certain special codes:
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010 international access
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0001 equivalent to 010 350 1 [Dublin]
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0055 from London only; calls charged at L rate
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0066 from London only; calls charged at a rate
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0077 from London only; calls charged at m rate
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Service codes begin with a 1:
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100 operator
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144 BT credit-card calls
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151 fault reporting
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153 international directory
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155 international operator
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192 directory
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Area codes are further grouped into "Charging Areas" (CA). For example:
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London CA: 71, 81
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Cambridge CA: 220, 223
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Madingley CA: 954
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The exception is the Tyne and Wear AC, which is three CAs (JXs [24]??,
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JXs 3??, and JXs 5??). This AC replaced three separate ACs (whose
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numbers I have forgotten), each of which had its own CA.
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BT has five charging rates for UK calls, and seven for international.
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The UK rates, in increasing order of cost, are L, a, b1, b, and m (m
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is more expensive than I, which is the cheapest international rate).
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Rates also vary by time:
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peak = M-F 0900-1300
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standard = M-F 0800-0900 and 1300-1800
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cheap = all other times
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(these do not apply to international calls).
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All calls within a CA are at rate L, as are those to "neighbouring"
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CAs. Each CA has a nominal centre. For all other calls, if the CA
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centres are within 56km, the call is at rate a, and otherwise it is at
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rate b. Rate b1 replaces rate b where BT feels under pressure from
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Mercury (London CA to Cambridge CA is b1, but to Madingley CA is b).
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Rate m ("mobile") is only used for calls to Vodaphone, Cellnet, and
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the special area codes. Hull is treated as a normal CA. Calls from BT
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to Mercury are charged as normal calls to the London CA.
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The real complications (you thought this wasn't enough ?) come when
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dialling calls other than by the full 0+ sequence. For this you need
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to know the subscriber number (SN).
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The one simple case is the all-figure areas. For each area, lines
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within the area are identified by seven digits (JX+LN), and calls are
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made by just dialling this number [in Tyne and Wear, calls *between*
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ACs must be prefixed with 90; this is being phased out].
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Everywhere else, we run into the "Named Exchange" (NE). An NE
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comprises a set of JXs, usually, but not always, in the same AC. A
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subscriber is identified by an exchange name followed by the SN, which
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is the LN with a prefix. The prefix can be empty, the last digit of a
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two digit JX, or the JX number. A catch to beware of is that sometimes
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two NEs have the same name but are distinguished by number length. For
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example, there is "Welwyn (six figure numbers)" and "Welwyn (four
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figure numbers)". These cover the same geographical area, but may have
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different ACs (these two don't). They are always in the same CA.
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As an example, the Madingley CA consists of:
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AC JX NE Prefix
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954 78 Crafts Hill 78
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954 21 Madingley 21
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954 3 Swavesey 3
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954 6 Willingham 6
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954 5 Cottenham 5
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954 4 Caxton (4 digits) none
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954 71 Caxton (6 digits) 71
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954 7 Elsworth none
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Calls to CAs other than at rate L are always dialled by the full 0+
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method. To call a subscriber on the same NE, it is just necessary to
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dial the SN. Other calls within the CA, and to CAs which are at the L
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rate, may have an alternate dialling method (not necessarily:
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Madingley to Huntingdon is rate L, but 0+ must be used; all calls from
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AC 71 or 81 to any other (or each other) must be dialled as 0+).
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Two alternate methods seem to be in common use: the "fan" method and
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the "slave" method (my names).
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The "fan" method is used at the main NE of a CA. Several prefixes in
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its AC are not used, but instead become dialling codes from the NE.
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For example, from Cambridge:
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8 -> AC 220 (same CA)
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91 -> AC 440 (different CA)
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92 -> AC 767 (different CA)
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93 -> AC 954 (different CA)
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94 -> AC 638 (different CA)
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95 -> AC 763 (different CA)
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96 -> AC 799 (different CA)
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98 -> AC 353 (different CA)
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These are then followed by the JX and LN. All other NEs in the same AC
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(not the same CA) can be called by dialling the JX and LN with no
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prefix (there are no cases of this in AC 223).
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[Amusing side-note. Someone blew it in specifying 8 -> AC 220. The JXs
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that were in AC 220 (21, 23, 24, 26, 27, 29, 5) did not occur in
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AC223. So there was actually no need for the dialling code. All of
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these except the last two have now been moved to Cambridge NE (and AC
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223) by simply changing the SN, without changing the JX+LN
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combination. The others will come soon (I have already seen people
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using "Cambridge 29xxxx" phone numbers).]
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The "slave" method is used at all other NEs in the same CA, and
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possibly in other CAs (All of Madingley CA is a slave of Cambridge NE
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in this sense). Calls to the master NE are made by dialling a single
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9 followed by the SN. All calls which are rate L, and which could be
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made from the master NE with a dialling code, are made by dialling 9
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followed by the sequence from the master NE.
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For example, from ACs 220 and 954, the following dialling codes exist:
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9 -> AC 223
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9+8 -> AC 220 (also used from Teversham (220 5) to West Wratting (220 29))
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9+91 -> AC 440 (not available from AC 954)
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9+92 -> AC 767
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9+93 -> AC 954 (also see below)
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9+94 -> AC 638 (not available from AC 954)
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9+95 -> AC 763 (not available from AC 954)
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9+96 -> AC 799 (not available from AC 954)
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9+98 -> AC 353
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In addition, a slave NE may also have other dialling codes not
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beginning with a 9. For example, in AC 954, to dial from Caxton (six
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digits), Cottenham, Crafts Hill, Madingley, Swavesey, and Willingham
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to any number in the AC is done by JX+LN, without any code. On the
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other hand, to dial from Elsworth to Caxton (four digits), or vice
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versa, the route via Cambridge must be used (i.e. 9+93+JX+LN).
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One final note. Slave exchanges have operator service provided by the
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master exchange. This means that emergency service is "9+99". On
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master exchanges, it is thus simply "99" (! for UK readers).
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-JUDGE DREDD/NIA
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[OTHER WORLD BBS]
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