The World of Computer Software/World_Of_Computer_Software-02-385-Vol-1of3.iso/v/v12-faq.zip/V12-FAQ.TXT

Text File | 1993-01-03 | 55KB | 1,129 lines

·    Subject: Frequently Asked Questions File for Telecom

The file which follows goes out automatically to each new subscriber
to the TELECOM Digest mailing list. It is also in the Telecom Archives,
however readers without the ability to use anonymous ftp to the
archives at lcs.mit.edu may have never seen it.

PAT

About the Digest itself:

TELECOM Digest was founded in August, 1981, by Jon Solomon. It has
been published continuously since that time. The location has changed
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Evanston, IL.

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The TELECOM Archives contains back issues of the Digest, as well as
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letter is a file showing how to use the Telecom Archives.

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                          ----------------

 From: [e-mail]

TELECOM Digest - Frequently Asked Questions - v.3   12 January 1992

This is a list of frequently asked questions made in the TELECOM
Digest. New versions of the list are occasionally made available
to deal with new and updated questions.

Much of the telecom information that is requested can be found in the
TELECOM Digest Archives, which is a collection of text files on
telecom topics. These archives are available for access through the
FTP protocol at lcs.mit.edu, or through another Archive site that has
been set up at letni.lonestar.org.  The monthly posting of the
description of TELECOM Digest should contain more details on how to
access these Archives.

This list is in the archives under the file name:

         frequently.asked.questions

Direct netmail requests to persons posting on topics of interest to
you may also be helpful. In fact, doing things "behind the scenes"
can be more productive as the Digest Moderator is frequently
swamped with other items. Future editions of this list could
include netmail addresses of contacts for certain topics (say
for ISDN, cellular, area codes/numbering plan, consumer protection
matters, etc); offers to that end would be appreciated.

The index to the Archives should be obtained and kept for reference.
This index has also occasionally appeared as a posting in the Digest.
You should also read the Archives file intro.to.archives to get a
better understanding of how the Archives operate.

A list of terms commonly used in TELECOM Digest may be obtained from
the Archives under the file names glossary.acronyms, glossary.txt and
glossary.phrack.acronyms.

Suggestions for other common questions, or corrections or other amendments
to this file may be made to [e-mail], [e-mail]
or [e-mail]. This file will be updated as
time and circumstances permit; all information herein should be considered
subject to correction or change.

Thanks to Nathan Glasser, Dan Boehlke and Maurice E. DeVidts and those
other inquiring TELECOM Digest minds for their frequent questions.
Tad Cook also noted an incorrect touch tone in the 1st edition of
FAQ, an error which was corrected since the second edition.

For v.3, the following people contributed comments, extra questions
and other updated information (or at least were the source):

Alan Barclay, ([e-mail])
Steve Beaty ([e-mail])
Rick Broadhead ([e-mail])
Gordon L. Burditt (sneaky.lonestar.org!gordon)
Tad Cook ([e-mail], [e-mail], or [e-mail])
David G. Cantor ([e-mail])
Tony Harminc ([e-mail])
Carl Moore ([e-mail])
Gary Morris ([e-mail])
Dan Sahlin ([e-mail])


- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

List of subjects questions covered as they appear in this list:

Technical

 - How do phones work?
 - What is a Central Office? What is a switch? What roles do Central
   Offices and switches play in the telephone network?
 - How many different types of switches are there, how do they differ,
   and what switches are most commonly found in use?
 - What frequencies do touch tones use for which numbers?
 - What are the A, B, C and D touch tone keys used for? Why are they
   not found on touch tone phone sets?
 - What is call supervision?
 - How can I find out what my own phone number is?
 - Are there other kinds of test numbers used?
 - Can a US modem or phone work in the UK, or some other European
   country? (Or vice versa, or in general for international substitution
   of phone equipment)
 - What do "tip" and "ring" mean?
 - What is "Caller ID" (or Call Display, or CNID (Caller Number
    Identification))?
 - How can I get specifications on how Caller ID service works?
 - What is the best way to busy a phone line?  I have a bank of modems
   which are set up as a hunt group.  When a modem dies I would like to
   be able to busy out the line that is disconnected, so that one of the
   other modems in the hunt group will take the call.
 - What is the difference between Caller ID/CNID and ANI?

Numbering

 - What is a numbering plan?
 - How was the country code system developed?
 - What is the correct way to write a telephone number for
   international use?
 - What are the prefix digits used in international dialing?
 - What does NPA, NNX, or NXX mean?
 - What happens when all the telephone numbers run out?
 - How is extra numbering capacity achieved in North America?
 - In North America, why does the long distance dialing within an area
   code often change so that 1 + home area code + number has to be
   dialed, or changed to just seven digits (like a local call)?
 - Is North America really running out of area codes?
 - How will we make room if North American area codes are running out?
 - What about expanding area/STD codes in other countries?
 - What is Bellcore?

Regulatory & Tariffs

 - What's this about the FCC starting a modem tax for those using
   modems on phone lines?
 - Why is a touch tone line more expensive than a rotary dial line
   (in many places)?
 - How come I got charged at a hotel for a call where no one answered?
   Why is the timing on some of the long distance carriers inaccurate?

Competition

 - Which countries have competitive long distance service?
 - What is a COCOT?
 - What is an AOS?
 - What is "splashing"?
 - Where can I find a list of equal access (10XXX) codes?
 - How can I tell who my default carrier is (or that of a 10XXX+ carrier)?

Features


 - What is the calling card "boing" and what is it made of?
 - How can I prevent the call waiting tone from beeping in mid-conversation?

Miscellaneous

 - Is there a way to find someone given just a phone number?

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

---------
Technical
---------

Q: How do phones work?

A: A file in the TELECOM Digest archives under the name "how.phones.work"
   is available and should explain some details of the workings of
   the common telephone.

Q: What is a Central Office? What is a switch? What roles do Central
   Offices and switches play in the telephone network?

A: A Central Office (CO) is the facility to which the telephones in
   a public telephone network are connected. It is the front line in
   terms of the whole telephone system; dial tone, telephone ringing,
   connection to other telephones, or outside trunks, is done here.

   A "switch" is a general term referring to facilities where
   telephone traffic is routed from one destination to another.
   The Central Office has a switch in a local sense; calls within
   a municipality can often be completed within a single switch.
   Beyond this, there are switches for long distance or regional
   traffic, many of which are not directly connected to user
   telephones.

   A hierarchy of switching centres was developed in North America.
   Level 5 switches are the most common and are generally the
   local Central Office switches. Level 4 switches are used in
   regional or larger local settings and occasionally are connected
   to customer telephones. Level 3, 2 and 1 switches serve larger
   regions in turn. In general, a call that cannot be handled at
   one level of switching (by reason of distance covered, or congestion
   at a given switch) is passed onto the next higher level until the
   connection is completed. The breakup of AT&T in the USA and the
   introduction of new services will no doubt have disrupted this
   hierarchy, but this illustrates how a call can progress from one
   place to another.

   A large city usually has many central offices, each serving a
   certain geographical area. These central offices are connected
   to other central offices for local calling, or to higher level
   switches, or into long distance networks.

Q: How many different types of switches are there, how do they differ,
   and what switches are most commonly found in use?

A: The original telephone switches were manual, operator-run switchboards.
   Today, these are generally found in developing countries or possibly
   in very remote locations as newer types of switches allow for
   connection to automatic telephone service.

   Step-by-step was the first widely-used automatic switching method.
   This was an electro-mechanical system which made use of rotating
   blades and mechanical selection of various levels. Dial pulses
   would be used to cause the switches to select switch groups until
   the whole number was dialed. Some step-by-step facilities still
   exist today, but will eventually be replaced by more modern
   forms of switching. Step-by-step, with its mechanical nature,
   can be difficult to troubleshoot and maintain, and does not
   inherently support touch tones or special calling features.

   Crossbar was the next step in electro-mechanical switching.
   Rather than the rotary/level switches used in step-by-step,
   connections were completed by means of a matrix of connectors.
   The configuration of crossbar matrix elements was under
   "common control" which could route the call along a variety
   crossbar elements. Step-by-step's "progressive control"
   could not be rerouted to avoid points of congestion in the
   switches but was rather at the mercy of which numbers would
   be dialed by the telephone users.

   Electronic switches were developed in the 1960's. These were
   often reed relay switches with an electronic common control
   faster than previous crossbar systems. The fewer moving parts
   there were, the better. Services such as call waiting or call
   forwarding would eventually be possible under electronic systems.

   Finally, the new digital electronic systems provide for a
   fully-programmable telephone operation. These are all-electronic
   systems without moving parts and full computerisation of control.
   Voice traffic would now be converted to digital format for use
   with digital transmission facilities. A wide variety of user
   services can be implemented such as sophisticated types of
   call forwarding or Caller ID or ISDN (Integrated Services
   Digital Network). Ultimately, all telephone subscribers will
   be served by such switches as these.

   Presently, various kinds of switching systems are in use, and
   the proportions of what technologies are in use in given regions
   will vary. The most common will eventually be the digital
   electronic systems. There are significant costs associated with
   upgrading the network to eventually use digital, fully-programmable
   switching, but the eventual goal is to modernise Central Offices
   and long distance networks to such switches. In the meantime, the
   various switching technologies in use must provide compatibility
   with each other.

Q: What frequencies do touch tones use for which numbers?

A: The touch tone system uses pairs of tones to represent the
   various keys. There is a "low tone" and a "high tone" associated
   with each button (0 through 9, plus * (star) and # (octothorpe
   or pound symbol). The low tones vary according to what
   horizontal row the tone button is in, while the high tones
   correspond to the vertical column of the tone button.

   The tones and assignments are as follows:

          1     2     3     A  :  697 Hz

          4     5     6     B  :  770 Hz
                                           (low tones)
          7     8     9     C  :  852 Hz

          *     0     #     D  :  941 Hz
        ----  ----  ----  ----
        1209  1336  1477  1633 Hz
               (high tones)

   When the 4 button is pressed, the 770 Hz and 1209 Hz tones
   are sent together. The telephone central office will then
   decode the number from this pair of tones.

   The tone frequencies were designed to avoid harmonics and
   other problems that could arise when two tones are sent
   and received. Accurate transmission from the phone and
   accurate decoding on the telephone company end are important.
   They may sound rather musical when dialed (and representations
   of many popular tunes are possible), but they are not intended to
   be so.

   The tones should all be +/- 1.5% of nominal.  The high frequency tone
   should be at least as loud, and preferably louder than the low
   frequency.  It may be as much as 4 db louder.  This factor is referred
   to as "twist."  If a Touchtone signal has +3db of twist, then the high
   frequency is 3 db louder than the low frequency.  Negative twist is
   when the low frequency is louder.

Q: What are the A, B, C and D touch tone keys used for?
   Why are they not found on touch tone phone sets?

A: These are extensions to the standard touch-tones (0-9, *, #)
   that had their origins in the miltary's phone network.
   The original names of these keys were FO (Flash Override),
   F (Flash), I (Immediate), and P (Priority) which represented
   priority levels that could establish a phone connection
   with varying degrees of immediacy, killing other conversations
   on the network if necessary with FO being the greatest priority,
   down to P being of lesser priority. The tones are more commonly
   referred to as the A, B, C and D tones respectively, and all
   use a 1633 Hz as their high tone.

   Nowadays, these keys/tones are mainly used in special applications
   such as amateur radio repeaters for their signalling/control.
   Modems and touch tone circuits tend to include the A, B, C and
   D tones as well. These tones have not been used for general
   public service, and it would take years before these tones could
   be used in such things as customer information lines; such
   services would have to be compatibile with the existing 12-button
   touch tone sets in any case.

Q: What is call supervision?

A: Call supervision refers to the process by which it is determined
   that the called party has indeed answered. Long distance calls
   and payphone calls are charged from the time the called party
   answers, and no charges should be assessed where the other
   end doesn't answer nor where the called party is busy or
   unreachable due to circuit problems.

Q: How can I find out what my own phone number is?

A: If the operator won't read your number back to you, and if you can't
   phone someone with a Calling # ID box, there are special numbers
   available that "speaks" your number back to you when dialed. These
   numbers are quite different from one jurisdiction to the next. Some
   areas use 200 222.2222; others just require 958; still others 311 or
   711 and others have a normally-formatted telephone number which can
   be changed on occasion (such as 997.xxxx).


   Such numbers exist in many countries; no set rule is used in
   determining such numbers other than that these are often assigned
   to codes outside normal customer number sequences.

Q: Are there other kinds of test numbers used?

A: Yes. Again, space (and available information) does not permit
   a complete list of what each telephone company is up to in
   terms of test numbers. The most common number is a "ringback"
   test number. When a two or three digit number is followed
   by all or the last part of your phone number, another dial
   tone occurs. Tests for dialing or ringing may then be done.

   Other numbers include intercom circuits for telephone company
   staff, or switching centre supervisors, or other interesting
   tests for call supervision or payphone coin tests. Again,
   this depends on the phone company, and such services are
   not usually found in the phone book, needless to say.

Q: Can a US modem or phone work in the UK, or some other European
   country? (Or vice versa, or in general for international substitution
   of phone equipment)

A: Often it can, provided that the AC Voltage and the physical jack
   are compatable or converted, and it can generate pulse dialing,
   as many exchanges are not equipped for touch tone.

   However, in most European countries it is illegal to fit non-approved
   equipment. In the UK approving equipment is the reponsability of BABT,
   and the penalty is confiscation of the equipment plus a fine of up
   to 2000 pounds sterling. Approved equipment has a mark, usually a
   sticker, of a green circle with the words "APPROVED for connection
   to the telecommunication system specified in the instructions subject
   to the condition set out in them" and the number of the BABT
   certificate. Non-approved items, if they are sold in the UK must
   have a sticker with a red triangle with similar wording execpt that
   it's saying the exact opposite. It's perfectly legal to sell
   non-approved equipment subject to the above, as there may be a
   valid reason for using it, just not on the UK network.

   In Canada, telephone equipment requires approval from the Canadian
   Department of Communications. Most equipment designed for North
   American conditions should be acceptable, but a small sticker
   from Communications Canada is normally used on the equipment
   to indicate such approval.

Q: What do "tip" and "ring" mean?

A: The conductors of a wire pair to a telephone set are referred to
   as tip (T) and ring (R). Tip (T) is usually the more positively
   charged of the two while Ring (R) tends to be more of a ground.
   However, two wires normally suffice to complete a connection
   between a telephone and the central office; any extra wiring
   would be for purposes such as grounding or for party line ringing.

   The Tip and Ring terms come from the parts of the plugs that
   were used for manual switchboards.

Q: What is "Caller ID" (or Call Display, or CNID (Caller Number
   Identification))?

A: This is a telephone company service that transmits the number
   of the party to your telephone during the ringing. A data
   receiver detects this signal and displays or otherwise accepts
   the number transmitted. Whether or not a number is transmitted
   depends on technical limitations (ie. calls placed from older
   technology switches may not be identifiable; long distance
   services may not be set up to provide end-to-end ID yet).

Q: How can I get specifications on how Caller ID service works?

A: The official documentation on how the Caller ID or calling line ID
   works is available for purchase from Bellcore. A description of
   what those documents are and how to get them is available in the
   TELECOM Digest Archives file caller-id-specs.bellcore. Check
   the Archives for any other relevant files that may appear
   such as descriptions of the standards and issues surrounding
   services such as Caller ID.

   In Canada, for information about the service (known there as
   Call Display) contact: Bell Canada, Director - Switched Network
   Services, 220 Laurier Avenue West, Ottawa, Ontario, K1G 3J4
   (tel: [phone]). The document is "Call Management Service
   (CMS) Terminal-to-Network Interface", Interface Disclosure ID - 0001,
   November 1989. The document at last report was free, at least
   within Canada. This document deals with Bell Canada's Call
   Display standards, and may not be applicable outside their
   service area (provinces of Ontario and Quebec, parts of the
   Northwest Territories).

   In general, the Caller ID information is passed to the set in
   ASCII using a 1200 baud modem signal (FSK) sent between the
   first and second rings.

Q: What is the best way to busy a phone line?  I have a bank of modems
   which are set up as a hunt group.  When a modem dies I would like to
   be able to busy out the line that is disconnected, so that one of the
   other modems in the hunt group will take the call.

A: "Our modem lines all enter on RJ21 "punchblocks" so I've got some
   rather nice clips that can be pushed over the terminals on the blocks
   and make contact with the pair that I want to busy out.  Between the
   two terminals on the clip I have a red LED and a 270 ohm 1/2w resistor
   in series.  As long as I get the clip on the right way, it busies out
   the line and lights up so I can see that I've got one of the lines
   busied out."

   "Since most of our modems have error correction, I've even gotten away
   with putting one of these on a line that's in use -- when the user
   disconnects, the line remains busy and I can then pull the modem at my
   leisure.  The modem's error correction fixes the blast of noise from
   the clip as I slip it in."

   - Brian

[Further notes [from Dan Boehlke]:  A setup like this is not necessary.
For most systems simply shorting tip and ring together will busy out
the phone line. Some older systems, and lines that do not have much
wire between the switch and the point at which it terminates will need
a 270 ohm 1/2 watt resistor. The resistor is necessary because on a
short line will not have enough resistance to make up for the lack
of a load. Most modern systems have a current limiter that will prevent
problems. Older system may not have a current limiter and may supply
more current than modern systems do. In the followup discussion, we
learned that we should not do this to incoming WATS lines and other
lines that will cause the phone companie's diagnostics centers to get
excited. A particular example was an incomming 800 number that was not
needed for a few days. The new 800 number was subscribed to one of
those plans that let you move it to another location in the event of
a problem. Well the AT&T diagnostic center saw the busy'ed out line as
a problem and promptly called the owner. -dan]

Q: What is the difference between Caller ID/CNID and ANI?

A: Caller ID or CNID or Call Display refers to a service offered to
   telephone customers that allows for display or identification of
   telephone numbers from which incoming calls are made. ANI, or
   Automatic Number Identification, refers to operations within the
   telephone network that allow for the registering of a long distance
   caller's number for billing purposes and not a public offering
   as such.

   Special services such as incoming number identification for
   toll-free or premium program lines (800 or 900 service in
   North America) make use of ANI information and pass this
   along to the called party.


---------
Numbering
---------

Q: What is a numbering plan?

A: A plan which establishes the format of codes and subscriber numbers
   for a telephone system or other communications system such as Telex.
   On a local level, subscriber numbers can have a certain number of
   digits (in some cases, the number of digits varies according to the
   exchange centre or digit seqeuence used). The local plan would allow
   for codes used to reach operators, directory assistance, repair, test
   numbers, etc. On a regional or even national level, there may need
   to be area codes or number prefixes established in order to route
   calls to the appropriate cities and central offices.

   The typical pattern is to use local numbers within a region, and use
   an STD (subscriber trunk dialing) or area code to call a number in
   another region. The most common method is to have STD/area codes begin
   with 0 (as in 071 or 081 for London, UK or 021 for Birmingham UK). The
   initial 0 would then indicate an STD code, while other digits (such as
   2 through 9) would be the initial digit of local numbers.

   In France, there are really two areas; Paris and everything else.
   All local numbers in France have eight digits. Paris uses an area
   code of 1, the rest of the country has no area code as such (just
   the local number, which does not begin with a 1).

   Some countries do not use an area code; instead, the local number
   is unique within the country. This often occurs in small nations
   but such plans are also active in Denmark and Singapore. Hong Kong
   got rid of its area codes recently and converted to seven-digit
   local numbers.

   North America is unusual in the world as the long distance prefix
   1 is commonly used before dialing an area codes plus local number
   (or on most areas, 1 plus number for numbers within an area code).
   Most countries include the prefix in their STD codes listing (021
   Birmingham, UK; 90 Helsinki, Finland) so that an initial prefix code
   is avoided. North American area codes have three digits, while local
   numbers have seven.


Q: How was the country code system developed?

A: In the early 1960s, a global numbering plan was devised so that the
   various national telephone systems can be linked; this used country
   codes of one to three digits in length, assigned according to geographic
   regions on the Earth. In fact, the system was developed from a numbering
   plan used in Europe to connect the various countries. International
   Telecommunications Union (ITU) documents from that time showed a
   numbering plan of two-digit country codes covering Europe and the
   Mediterranean Basin countries and even described overseas access codes
   used in various countries (France 19, UK 010 - most still in use today).
   Many country codes from that original numbering plan were used in the
   worldwide plan such as France 33, UK 44 although many codes had to
   be renumbered.

   The world numbering zones (with initial country code digits) are:

       1        North America
       2        Africa
       3 and 4  Europe
       5        South America
       6        South Pacific countries (Australia)
       7        former USSR (now Commonwealth of Independent States)
       8        Southeast Asia (Japan, China)
       9        Middle East countries (India, Saudi Arabia)

   The TELECOM Digest Archives has country code listings, including
   a detailed set which indicates area or STD codes used within country
   codes as they would be dialed in international dialing (excluding
   domestic long distance prefix digits).

Q: What is the correct way to write a telephone number for
   international use?

A: The method as recommended by the CCITT (an international
   telecommunications standards committee) is to use the plus
   sign then the country code, then the STD code (without any
   common STD/area code prefix digits) and the local number.
   Some examples are:

    City             Domestic Number    International Format
    ---------------  -----------------  --------------------
    Toronto, Canada  [phone]     + 1 416 967 1111
    Paris, France    (1) 3333 3333      + 33 1 3333 3333
    Lyon, France     7777 7777          + 33 7777 7777
    Birmingham, UK   021-123 4567       + 44 21 123 4567
    Colon, Panama    41-2345            + 507 41 2345

   In most cases, the initial 0 of an STD code will not form part of the
   international format number. Some countries use a common prefix of 9
   (such as Finland or Colombia). Some countries STD codes can be used
   particularly where prefix digits are not necessary (North America,
   Mexico).

   The important consideration is that the digits following the +
   represent the number as it would be dialed on an international call
   (that is, the telephone company's overseas dialing code followed
   by the digits after the + sign in the international format).

Q: What are the prefix digits used in international dialing?

A: This depends on the country from which an international call is
   placed. The recommended international prefix is 00 (followed by
   the international format number). Some of the exceptions are:

     Australia    0011            Nigeria        009
     Austria      900             Mexico         95
     Denmark      009             Norway         095
     Finland      990             North America  011
     France       19              Russia         810
     Ireland      16              Spain          07
     Netherlands  09              United Kingdom 010

  (Netherlands international code is expected to change to 00 soon)

Q: What does NPA, NNX, or NXX mean?

A: NPA means Numbering Plan Area, a formal term meaning a
   North American area code (like New York 212, Chicago 312,
   Toronto 416 etc).

   NNX refers to the format of the telephone number's prefix;
   (the first three digits of a phone number). The N represents
   a digit from 2 to 9; an X represents any digit 0 to 9. Thus,
   NNX prefixes can number from 220 to 999, as long as they do
   not have a 0 or 1 as the middle digit.

   NXX means any prefix from 200 to 999 could be represented,
   allowing for any value in the middle digit. Obvious special
   exceptions include 411 (directory assistance) and 911 (emergency).

Q: What happens when all the telephone numbers run out?

A: With demand for phone numbers increasing worldwide, the capacity
   given by a certain number of digits in a numbering plan will
   tend to be exhausted.

   In whatever country, capacity expansion can be done by such measures
   as adding an extra digit to the local number (as was done in Tokyo
   recently or in Paris, France some years back). Extra area/STD codes
   can be assigned, such as splitting a region's codes (London UK was
   originally STD code 01, now split to 071 and 081; Los Angeles in the
   U.S. was originally area code 213, then split to add an 818 area,
   and recently another split of 213 created the new 310 area).

Q: How is extra numbering capacity achieved in North America?

A: Within an area code, there are a maximum number of prefixes
   (ie. first three digits of a phone number) that can be assigned.
   In the original telephone "numbering plan", up to 640 prefixes
   could be assigned per area code (of the NNX format, 8 * 8 * 10).
   Yet, prefixes get used up due to growth and demand for new numbers
   (accelerated by popularity of separate fax or modem lines, or by
   new services such as the distinctive ringing numbers that ring a
   single line differently depending on which phone number was dialed).

   When the prefixes of NNX format run out, there are two options
   in order to allow for more prefixes, and in turn more numbers:

      1) "splitting" the area code so that a new area code can
         accomodate new prefixes, or

      2) allowing extra prefixes to be assigned by changing from
         NNX format to NXX format.

   The preferred option is to go with 2) first, in order to avoid having
   a new area code assignment. Yet, this gives the area code a maximum of
   160 new prefixes, or 8 * 10 * 10 = 800. When the NXX format prefixes
   are used up, then 1) is not optional. New York and Los Angeles are two
   regions that have gone from NNX to NXX format prefixes first, then
   their area codes were split.

   Interestingly enough, some area codes have split even though there
   was no change from NNX format prefixes to NXX. Such splits have
   occurred in Florida (305/407) and Colorado (303/719). The precise
   reasons why a change to NXX-style prefixes was not done in those
   cases is unknown to this author, but switching requirements in those
   areas, plus telephone company expenses in changing from NNX to NXX
   format (and the likelihood of an eventual area code split) are
   likely factors in these decisions.

   Note that it is prefixes, and not necessarily the number of telephones,
   that determines how crowded an area code is. Small exchanges could use
   a whole prefix for only a few phones, while an urban exchange uses most
   of the 10 000 possible numbers per prefix. Companies, paging, test
   numbers and special services can be assigned their own prefixes as
   well, such as the 555 directory assistance prefix (555.1212).

Q: In North America, why does the long distance dialing within an
   area code often change so that 1 + home area code + number has
   to be dialed, or changed to just seven digits (like a local call)?

A: When prefixes change to NXX, that means that the prefix numbers
   can be identical to area codes. The phone equipment is no longer
   able to make an easy distinction between what is an area code and
   what is a prefix within the home area code, based on the first
   three digits. For instance, it is hard for central offices to
   tell the difference between 1+210 555.2368 and 1+210.5552

   Thus, 1 + area code + number for all calls is used in many
   area codes. Or ... just dialing seven digits within the area
   code for all calls, local or long distance (thus risking
   complaints from customers who thought they were making a local
   call when in fact the call was to a long distance exchange).

   It is up to each phone company to decide on how to handle prefix
   and dialing changes. The rules can change from place to place.

Q: Is North America really running out of area codes?

A: Indeed, there are only a few possible area codes that can be
   assigned from the existing format. At present, all area codes
   have a 0 or 1 as the middle digit (212, 907, 416, 708, etc).
   However, the only standard area codes left to be assigned in
   that format would be 210, 810 and 910. It may be possible to
   free 610 from its usage in Canadian TWX service, and 710 from
   what is apparently reserved for government services.

   These exclude special cases such as area codes ending in -00 for
   special services like 800 or 900. Also, -11 area codes could
   be confused with services like 411 (directory assistance) or
   911 (emergency); indeed, a few places require 1+411 for directory
   assistance.

Q: How will we make room if North American area codes are running out?

A: Bellcore, which oversees the assignment of area codes and
   the North American Numbering Plan in general, has made a
   recommendation that "interchangeable" area codes be allowed

   as of July 1995. That means that there no longer need to be
   a 0 or 1 as the middle digit of an area code, and in fact the
   area code will become NXX format. While some suggest that
   eight-digit local numbers or four-digit area codes be
   established, the interchangeable area code plan has been
   on the books for many years.

   One aspect of the plan is that, initially, the new area codes
   will end in 0 (such as 220, 650, etc). This would make it
   easier on a few area codes so that they could conceivably
   retain the ability to dial 1+number (without dialing the home
   area code) for long distance calls within the area code, provided
   that they have not assigned prefixes ending in zero that would
   conflict with new area codes. That option is not possible for
   many area codes that have already assigned some prefixes
   of "NN0" format, however. Eventually, the distinction between
   area code and prefix formats would be completely lost.

   It is conceivable that the date for changing North America
   over to interchangeable area codes (yes, this change will be
   felt throughout the U.S. and Canada) could be moved to an
   earlier date, or that the existing area codes plus the few
   waiting to be assigned will have to make do until 1995,
   causing some service shortages in some areas. Another possibility
   includes using some of the special -00 or -11 codes (like 200
   or 311) as area codes as a last resort.

Q: What about expanding area/STD codes in other countries?

A: Many countries tend to use variable numbers of digits in the local
   numbers and STD/area code numbers, thus there is often flexibility
   in assigning new codes or expanding the capacity of codes. Sometimes
   codes are changed to provide for extra capacity or to allow for
   a uniform numbering plan such as ensuring the total number of digits
   of the STD/area code plus the local number is constant within a
   country.

   In the UK, it is reported that the digit '1' will be added before
   all STD codes as of Easter Sunday 1994 in order to create extra
   capacity for STD codes.

   In North America, the second digit of an area code will no longer
   be restricted as of July 1995; this will allow for a large increase
   in the number of available North American area codes.

Q: What is Bellcore?

A: Bellcore, or Bell Communications Research, is a company that does
   a variety of things for the telephone system in North America. It
   assigns area codes, develops and sells technical documents relating
   to the operation of the phone system, and does research and
   development on various communications technologies. Recently,
   Bellcore did development on MPEG, a video data compression method
   to allow reasonably-quality transmission of entertainment-quality
   video on a 1.5 Mb/s communications link.

   The Bellcore catalogue can be ordered by calling 1 800 521 CORE
   (that is, 1 800 521 2673) within the USA, or [phone]
   outside the USA ([phone] is the fax number).


--------------------
Regulatory & Tariffs
--------------------

Q: What's this about the FCC starting a modem tax for those
   using modems on phone lines?

A: This is one of those tall urban legends, on the order of the
   Craig Shergold story (yes, folks, Craig's doing okay as of last
   report and he doesn't need cards of any kind). This is an
   unsubstantiated rumour and as such should not be acted on.
   Official information from the FCC would come forth were such a
   proposal to occur.

   Reading up on regulators' announcements is a good pastime in
   any case, as one can get the information from the source and
   watch for such concerns.

  ------------------
TELECOM Moderator's Note, appended 1-1-93:  Here is another response
to the 'modem tax' question which pops up all the time.

From: mc/G=Brad/S=Hicks/OU=[e-mail]
Date: 17 Nov 92 14:59:51 GMT

I got another copy of the FAQ.  I glanced through it to see if
anything had changed and found no surprises, but I did see something
that needed just a bit more detail.  For your consideration: a
possibly clearer answer on the "modem tax" question.  Edit as desired.

Q: What's this about the FCC starting a modem tax for those
   using modems on phone lines?

A: This is one of those tall urban legends, on the order of the
   Craig Shergold story (yes, folks, Craig's doing okay as of last
   report and he doesn't need cards of any kind).  It started when
   the FCC took up a proposal that, if it had passed, would have
   raised the rate that {some} modem users paid ... notably, those
   who have set up their own long distance networks for public use,
   like CompuServe.  The proposal was not enacted into law.

   Nevertheless, this proposal, or one even worse, could come up
   again in the future.  Here's how to tell the facts from the urban
   legends.  (1) Demand documentation; don't act until you see a
   copy of the FCC proposal.  (2) Once you have the proposal, look
   at the number.  It will be in the form yy-n, yy-nn, or yy-nnn.
   The first number, before the hyphen, is the year.  If, for
   example, it's the infamous 85-79, you know it was the 79th
   proposal all the way back in 1985, and no longer matters.  (3)
   If you do see an up-to-date proposal, read it carefully.  If you
   can't tell what part of it enacts a "modem tax", demand that the
   person who wants you to act explain it to you.  If they can't,
   or won't, then (and only then) bring it up on Telecom Digest,
   making sure that you always include the FCC proposal's number,
   so that people know which document you're talking about.

 ------------------

Q: Why is a touch tone line more expensive than a rotary dial
   line (in many places)?

A: This has been an occasional debate topic in the Digest. Indeed,
   there can be a surcharge from $1 to $3 per month to have the
   ability to dial using touch tone. In modern equipment, touch
   tone is actually better and cheaper for the phone company
   to administer that the old pulse/rotary dialing system.

   The tone dialing charge can be attributed to the value of
   a demanded service; tone is better, thus a premium can be
   applied for this privilege. Also, it is something of a holdover
   from the days when tone service required extra expense to decode
   with the circuitry originally available. This is especially
   true on crossbar exchanges, or where tone would have to be
   converted to dial pulses as is the case with step-by-step
   exchange equipment. Today, integrated circuits are readily
   available for decoding the tones used in dialing, and are
   a standard part of electronic switching systems.

   Some telephone companies have abandoned a premium charge
   for tone dialing by including this in local service.
   Others still hold to some form of tone surcharge.

Q: How come I got charged at a hotel for a call where no
   one answered? Why is the timing on some of the long
   distance carriers inaccurate?

A: Where real call supervision is unavailable or inconvenient,
   a ploy used by some call billing systems is to guess when
   a call might be answered. That is, a customer dials the call,
   and the equipment times the progress; after a certain point
   in time the billing will commence whether or not the party
   at the other end actually answers the phone. Thus, calls
   left ringing for more than five or six rings can be billed.
   Adding to the problem is the fact that calls don't necessarily
   start ringing at a fixed time after the last digit is dialed.

   Needless to say, some calls can be left uncharged in this
   scheme. Should the call be answered and completed before the
   billing timer goes off, the call won't be billed.

   There are reports that California requires proper billing
   and supervision of calls. Other areas may adopt similar
   requirements.

-----------
Competition
-----------

Q: Which countries have competitive long distance service?

A: Most countries still rely on a single telephone company for their
   local and long distance services. The United States has an open
   competition in terms of long distance services (ie. a choice of
   carriers such as AT&T, MCI, Sprint, Metromedia/ITT, Allnet, ATC).

   The UK has a duopoly long distance situation: British Telecom
   and Mercury can provide long distance services but that could
   be challenged as other companies wish to provide long distance
   services.

   Canada has limited competition in terms of such things as fax
   communication services and various long distance/local service
   resellers, aimed at business interests; the question of fully
   competitive long distance in Canada should be answered in 1992
   as a decision regarding the Unitel and BCRL proposals is rendered.

   New Zealand has just allowed Clear Communications to compete
   in long distance. Australia now has Optus as a long distance
   competitor. Japan has some competition in public long distance

   services, also.

   There are signs of future competition in the "local loop", or
   local exchange services, also. It may one day be possible to
   have a choice of companies to provide the "dial tone", and not
   just the long distance calling.

Q: What is a COCOT?

A: Customer-Owned Coin-Operated Telephone, or perhaps Coin-Operated
   Customer-Owned Telephone. Essentially, this is a privately-owned
   public telephone as opposed to the traditional payphone that is
   owned and operated by the local telephone company. Most COCOTs exist
   in the United Stated; their status is not too well-known outside
   the U.S.; certainly there are no approved COCOTs in Canada as
   such and are also likely rare or nonexistent in other nations.

   The COCOT is the target of much scorn, as it often delivers less than
   what one would hope for in competition. Cited deficiencies of many
   of these units include prohibiting access to carriers like AT&T, use
   of default "carriers" that charge exorbitant rates for long distance
   calls, etc. Some of them have had problems when new area codes were
   used, such as the recent 903 (Texas) or 908 (New Jersey) areas.

Q: What is an AOS?

A: AOS is short for Alternative Operator Service. That is, a company
   other than a long distance carrier or local telephone company
   that provides operator assisted services for long distance. Normally
   this involves having operator staff handle billing and the necessary
   dialing, but the AOS companies use an existing long distance service
   rather than set up their own network. Using an AOS, whether for a
   collect call or credit card call can be expensive.

Q: What is "splashing"?

A: Suppose you place a call from city A to city B using an AOS based
   in city C. The call is considered to be "splashed" if the billing
   for the call is based on the distance between city C (AOS) and
   city B (destination) rather than between cities A and B as
   one traditionally expects such calls to be billed. Thus, if the
   splashed distance (C-B) is much longer than the origin-destination
   (A-B) distance, extra money gets charged somewhere.

Q: Where can I find a list of equal access (10XXX) codes?

A: The TELECOM Digest Archives has lists of these codes.
   They are contained in the files occ.10xxx.access.codes and
   occ.10xxx.list.updated in the Archives at lcs.mit.edu or
   letni.lonestar.org. New information on these codes, or
   other access codes, appears in TELECOM Digest on occasion
   as well.

Q: How can I tell who my default carrier is (or that of a 10XXX+
   carrier)?

A: Dial 1 700 555.4141, and that should get a recording indicating
   the default carrier. This should be a free call. From regular
   lines, dialing 10XXX + 1 700 555.4141 can yield the identifying
   recordings of other carriers. On payphones, AT&T is always a
   "default" carrier for coin calls (not for calls placed on other
   carriers cards, though), thus their recording is heard whatever
   carrier access codes are used.

--------
Features
--------

Q: What is the calling card "boing" and what is it made of?

A: When a North American call is dialed as 0 + (area code if necessary)
   + number, a "boing" is heard after the number is dialed. This is the
   prompt to enter a telephone company calling card number to bill the
   call with, or to select the operator (0) for further handling, or in
   a growing number of areas to specify collect or third number billing
   for the call.

   The boing consists of a very short burst of the '#' touch tone, followed
   by a rapidly decaying dial tone. The initial '#' tone is used in case
   any tone-pulse converters exist on the line; such converters use the
   '#' to disable conversion of tones to dial pulses, a conversion which
   would interfere with card number dialing.

Q: How can I prevent the call waiting tone from beeping in
   mid-conversation?

A: If you place the call, and don't want to get interrupted, a call
   waiting suppression code is dialed before dialing the call itself.
   The most common code for this in North America is *70 or 1170 (on
   rotary dial phone lines). 70# (or 70 and wait on rotary phone) could
   also be used in some areas. Other countries will have special codes
   for this, and will vary in terms of capabilities offered.

   Local phone companies in some areas charge installation and monthly
   fees for 'Cancel Call Waiting', and you must subscribe for this to
   work. In some areas it comes free with Call Waiting. In some other
   areas it's unavailable at any price.

   Thus, to call 555.0000 so that call waiting is disabled, dial *70
   (or whatever the correct code is for your area), wait for another
   dial tone, then dial 555.0000 as usual.

   Suppressing call waiting tone on an *incoming* call may be possible
   depending on how your phone company has set the central office.
   One possible way of doing this is to flash your switch-hook briefly,
   see if a dial tone comes on, then try dialing the call waiting
   suppress code (*70 or whatever). Southwestern Bell, for instance,
   uses a variant of this: <flash hook> *70 <flash hook> (ie. a second
   hook flash required). The methods are not guaranteed, however; your
   phone company might be able to give a better answer if the preceding
   doesn't work.

   NOTE: each phone company will determine the capabilities of Call
   Waiting features, and what codes will be used to activate them,
   and what costs the service will be provided at. The codes are
   not necessarily the same from place to place. Please consult your
   phone company for official information in your particular area
   if any of the above codes do not work properly. Also check the
   phone book introductory pages as these sometimes include
   instructions on how to use special calling services such as
   Call Waiting.

-------------
Miscellaneous
-------------

Q: Is there a way to find someone given just a phone number?

A: Sometimes. There are often cross-referenced city indexes available in
   libraries and other places that have lists ordered by the phone number.
   These directories go by names such as Mights or Strongs or other
   companies. Unlisted numbers are not listed, nor are they intended to
   be traced by the general public. One catch is that such directories
   are necessarily out of date shortly after their publication what with
   the "churn" of changing telephone numbers and addresses.

   In addition, there are phone numbers provided by telephone companies
   that connect to live lookup services. Operators at these numbers will
   determine a person according to the phone number. Only a few of these
   lookup numbers are intended for the general public (eg. Chicago and
   Tampa). Some countries have also provided number to name lookup as a
   matter of normal telephone service, although these are often chargeable
   calls. Otherwise, most of these lookup numbers are for internal telephone
   company usage. Again, unlisted numbers are not intended to be provided
   by these services.

   Private detectives seem to have other means of getting these
   numbers, but that's another story...

( end of list )

                         ---------

Send future Frequently Asked Questions direct to [e-mail],
[e-mail] or other addresses mentioned at the beginning of
this document. Do NOT use any of the TELECOM Digest addresses for
correspondence regarding the FAQ unless all other addresses are
unreachable.

                          ----------

And there you have the Telecom FAQ file ... perhaps some people will
read it *before* they send in questions and commentaries to the
Digest. This file is also in the Telecom Archives if you need another
copy.

Happy New Year to all!


Patrick Townson
TELECOM Digest Moderator