The following words relate to telephone numbering, and may appear in WTNG:
An area code is used within many nations to route calls to a particular
city, region or special service. Depending on the nation or region, it
may also be referred to as a numbering plan area, subscriber
trunk dialling code, national destination code or routing
A country code is used to reach the particular telephone system
for each nation or special service.
The World Zone is the first digit of a country code. This generally
corresponds to a global region, but some country codes are an exception
(e.g. +299 Greenland is not in Africa, but there was not enough room
in Europe's two World Zones at the time Greenland's country code was
originally assigned). Special international services such as freephone or
satellite telephone have country code assignments under World Zones 8 and 9.
closed numbering plan
A closed numbering plan refers to a telephone numbering scheme
that has a fixed number of digits, not counting special service codes.
The North American Numbering Plan +1 is
an example, because there are always ten digits associated with each national
number - 3 digits of area code followed by 7 digits of subscriber number.
Australia +61 has become another example
of a closed numbering plan.
A trunk prefix refers to the initial digit(s) to be dialled in
a domestic call, prior to the area code (if necessary) and the subscriber
number. 0 is the trunk prefix in most nations. In the
North American Numbering Plan +1 it is 1;
it is merely co-incidental that the country code and trunk prefix are
both 1. For calls to another country code, the trunk prefix is generally
omitted. For example, a call to London, UK within the UK would be dialled
as 020 #### #### but from outside the UK, the initial 0 (trunk prefix)
is omitted: +44 20 #### ####. Some nations do not use a trunk prefix,
which means only the subscriber number is dialled in those cases.
An international prefix is the code dialled prior to an
international number (country code, area code if any, then subscriber number).
In most nations, this will be 00. In some nations in Asia, this is 001
(in some cases, alternate codes are available to select the particular
international carrier). In North America, this is 011 (or 01 for special
call processing - collect, person-to-person, calling card, etc.).
closed dialling plan
A closed dialling plan refers to a national requirement to use
all digits of a national number (often including a trunk prefix) to place
a call, whether local or long distance. The current systems in France
(as of October 1996) and Belgium
(as of January 2000) are examples of closed dialling plans.
geographic area code
A geographic area code refers to an area code that has a defined
geographic boundary. Geographic area codes are for conventional fixed-line
(or land line) services terminating at fixed points. Non-geographic area
codes would include wireless (cellular and pager whose subscribers could
be located at variable points), or toll-free services (usually assignable
on a nation-wide basis, without being bound to specific regions), or premium
and personal number services (again, assignable anywhere within a nation).
local number, subscriber number
The local number or subscriber number represents the specific
telephone number to be dialed, but does not include the country code,
area code (if applicable), international prefix or trunk prefix.
The term national number in this document refers to the combination
of area code (if any) plus local number.
permissive dialling period
A permissive dialling period is a time during which an old and
new numbering format may be used to place calls to a subscriber. This is
used to provide a transition phase, to allow telephone users time to adjust
to a new numbering scheme.
After a permissive dialling period, the old numbering format becomes invalid
and the new numbering format is said to be mandatory.
A splash cut means a numbering change that is made without any
interim permissive dialling period. The old numbering is suddenly replaced
by a new numbering format, on a date and time scheduled by the telephone
regulator and/or carrier(s).
An exhaust occurs when all available numbers in a numbering space
have been assigned for some purpose - e.g. no more subscriber numbers can be
assigned for an area code, because all assignable numbers are in use or
otherwise unavailable for use. Normally, relief measures would be taken
to add numbering capacity well before an exhaust occurs, usually through the
assignment of additional area codes or extra digits.
An overlay refers to the assignment of a new numbering range
in the same territory as an existing numbering range. For example, a new
area code would be added within an existing area code's boundaries. Two
subscriber lines in the same premises could then be assigned different
sterilisation refers to a period in which a decommissioned
numbering range is left unused. For example, an area code may be changed to
allow its range to be used for future area codes. However, it may not be
desirable to re-assign the old code immediately, as callers may still
attempt to use the old code for some time.
When a telephone number is changed by adding a digit before the existing
number, the digit is said to be prepended. On the other hand, a
digit added after the end of an existing telephone number is
Note that some numbering terms, such as prefix, often mean different
things in different places e.g. a prefix could be the digits dialled
before a long distance call, or it could refer to an initial part of a
subscriber number that identifies a location or type of service.
WTNG attempts to consistently use the terms trunk prefix and
international prefix as defined above.
plus sign (+) notation for country codes
Where a plus sign (+) is used, this indicates a country code (e.g. +33
for France), or it may indicate the initial portion or complete number
as it is dialed in international format (e.g. +52 5 represents Mexico City
- +52 Mexico country code, then area code 5).
A company providing a telephone service (whether wireline, wireless, etc)
is a carrier or operator.
WTNG does not have the final word on telecom terminology; the job of
describing the rapidly-changing field of telecom numbering is a continuing
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