BIOC Agent 003's course in basic telecommunication
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******BIOC Agent 003's course in*******
* ========================== *
* =BASIC TELECOMMUNICATIONS= *
* ========================== *
* Part VII *
After most neophyte phreaks overcome their fascination with Metro codes and
WATS extenders, they will usually seek to explore other avenues in the vast
phone network. Often they will come across references such as "simply dial KP +
2130801050 + ST for the Alliance teleconferencing system in LA." Numbers such
as the one above were intended to be used with a blue box; this article will
explain the fundamental principles of the fine art of blue boxing.
In the beginning, all long distance calls were connected manually by operators
who passed on the called number verbally to other operators in series. This is
because pulse (aka rotary) digits are created by causing breaks in the DC
current (see Basic Telcom V). Since long distance calls require routing
throughvarious switching equipment and AC voice amplifiers, pulse dialing
cannot be used to send the destination number to the end local office (CO).
Eventually, the demand for faster and more efficient long distance (LD) service
caused Bell to make a multi-billion dollar decision. They had to create a
signaling system that could be used on the LD Network. Basically, they had two
 To send all the signaling and supervisory information (ie, ON & OFF HOOK)
over separate data links. This type of signaling is referred to as out-of-band
 To send all the signaling information along with the conversation using
tones to represent digits. This type of signaling is referred to as in-band
Being the cheap bastard that they naturally are, Bell chose the latter (and
cheaper) method -- IN-BAND signaling. They eventually regretted this, though
IN-BAND SIGNALING PRINCIPLES:
When a subscriber dials a telephone number, whether in rotary or touch-tone
(DTMF), the equipment in the CO interprets the digits and looks for a convenient
trunk line to send the call on its way. In the case of a local call, it will
probably be sent via an inter-office trunk; otherwise, it will be sent to a
toll office (class 4 or higher -- see Telcom IV) to be processed.
When trunks are not being used there is a 2600 Hz tone on the line; thus, to
find a free trunk, the CO equipment simply checks for the presence of 2600 Hz.
If it doesn't find a free trunk the customer will receive a re-order signal
(120IPM busy signal) or the "all circuits are busy..." message. If it does find
a free trunk it "seizes" it -- removing the 2600 Hz. It then sends the called
number or a special routing code to the other end or toll office.
The tones it uses to send this information are called multi-frequency (MF)
tones. An MF tone consists of two tones from a set of six master tones which
are combined to produce 12 separate tones. You can sometimes hear these tones
in the background when you make a call but they are usually filtered out so
your delicate ears cannot hear them. These are NOT the same as touch-tones.
To notify the equipment at the far end of the trunk that it is about to receive
routing information, the originating end first sends a Key Pulse (KP) tone. At
the end of sending the digits, the originating end then sends a STart (ST)
tone.Thus to call 914-359-1517, the equipment would send KP + 9143591517 + ST
in MF tones. When the customer hangs up, 2600 Hz is once again sent to signify a
disconnect to the distant end.
In the November 1960 issue of The Bell System Technical Journal, an article
entitled "Signaling Systems for Control of Telephone Switching" was published.
This journal, which was sent to most university libraries, happened to contain
the actual MF tones used in signaling. They appeared as follows:
1 700 + 900 Hz
2 700 + 1100 Hz
3 900 + 1100 Hz
4 700 + 1300 Hz
5 900 + 1300 Hz
6 1100 + 1300 Hz
7 700 + 1500 Hz
8 900 + 1500 Hz
9 1100 + 1500 Hz
0 1300 + 1500 Hz
KP 1100 + 1700 Hz
ST 1500 + 1700 Hz
11 (*) 700 + 1700 Hz
12 (*) 900 + 1700 Hz
KP2 (*) 1300 + 1700 Hz
(*) Used only on CCITT SYSTEM 5 for special international calling.
Bell caught wind of blue boxing in 1961 when it caught a Washington state
college student using one. They originally found out about blue boxes through
police raids and informants. In 1964, Bell Labs came up with scanning
equipment,which recorded all suspicious calls, to detect blue box usage.
installed in CO's where major toll fraud existed. AT&T Security would then
listen to the tapes to see if any toll fraud was actually committed. Over 200
convictions resulted from the project. Surprisingly enough, blue boxing is not
solely limited to the electronics enthusiast; AT&T has caught businessmen, film
stars, doctors, lawyers, college students, high school students and even a
millionaire financier (Bernard Cornfeld) using the device. AT&T also said that
nearly half of those that they catch are businessmen.
Of course, phone phreaks have achieved an almost cult status. They have also
had their fair share of media. In October 1971, Esquire published the infamous
"Secrets of the Little Blue Box" article which featured phreaks such as Captain
Crunch, who took his name from the cereal which one gave away whistles that
produced a perfect 2600 Hz pitch; Joe Engressia, the blind phreak; and Mark
Bernay, one of the nation's first and oldest phreaks. Others such as Apple
computer co-founders Steve Wozniak & Steve Jobs have also had blue box
backgrounds. 1971 also saw the publication of the first issue of YIPL, the
phonephreak newsletter, (now TAP) under the editorship of supreme yippie Abbie
To use a blue box, one would usually make a free call to any 800 number or
distant directory assistance (NPA-555- 1212). This, of course, is legitimate.
When the call is answered, one would then swiftly press the button that would
send 2600 Hz down the line. This has the effect of making the distant CO
equipment think that the call was terminated and it leaves the trunk hanging.
Now, the user has about 10 seconds to enter in the telephone number he wished
todial -- in MF, that is. The CO equipment merely assumes that this came from
another office and it will happily process the call. Since there are no records
(except on toll fraud detection devices!) of these MF tones, the user is not
billed for the call. When the user hangs up, the CO equipment simply records
that he hung up on a free call.
Bell has had 20 years to work on detection devices; therefore, in this day and
age, they are rather well refined. Basically, the detection device will look
for the presence of 2600 Hz where it does not belong. It then records the
calling number and all activity after the 2600 Hz. If you happen to be at a
fortress fone, though, and you make the call short, your chances of getting
caught are significantly reduced (see Telcom VI). Incidentally, there have been
rumors of certain test numbers (see Telcom II) that hook directly into trunks
thus avoiding the need for 2600 Hz and detection!
Another way that Bell catches boxers is to examine the CAMA (Centralized
Automatic Message Accounting) tapes. When you make a call, your number, the
called number, and time of day are all recorded. The same thing happens when
you hang up. This tape is then processed for billing purposes. Normally, all
free calls are ignored. But Bell can program the billing equipment to make note
of lengthy calls to directory assistance. They can then put a pen register
(akaDNR) on the line or an actual full-blown tap. This detection can be
avoided by making short-haul (aka local) calls to box off of.
It is interesting to note that NPA+555- 1212 originally did not return answer
supervision. Thus the calls were not recorded on the AMA/CAMA tapes. AT&T
changed this though for "traffic studies!"
Besides detection devices, Bell has begun to gradually redesign the network
using out-of-band signaling. This is known as Common Channel Inter-office
Signaling (CCIS). Since this signaling method sends all the signaling
information over separate data lines, blue boxing is impossible under it.
While being implemented gradually, this multi-billion dollar project is still
strangling the fine art of blue boxing. Of course until the project is totally
complete, boxing will still be possible. It will become progressively harder
tofind places to box off of, though. In areas with CCIS, one must find a
directory assistance office that doesn't have CCIS yet. Area codes in Canada
and predominately rural states are the best bets. WATS numbers terminating in
non-CCIS cities are also good prospects.
Another way that may help to avoid detection is too add some "pink noise" to
the 2600 Hz tone.
Since 2600 Hz tones can be simulated in speech, the detection equipment must be
careful not to misinterpret speech as a disconnect signal. Thus a virtually
pure 2600 Hz tone is required for disconnect.
Keeping this in mind, the 2600 Hz detection equipment is also probably looking
for pure 2600 Hz or else is would be triggered every time someone hit that note
(highest E on a piano = 2637 Hz). This is also the reason that the 2600 Hz
tone must be sent rapidly; sometimes, it won't work when the operator is saying
"Hello, hello." It is feasible to send some "pink noise" along with the 2600
Hz. Most of this energy should be above 3000 Hz. The pink noise won't make it
into the toll network (where we want our pure 2600 Hz to hit) but it should
make it past the local CO and thus the fraud detectors.
While step-by-step details for the construction of a blue box is beyond the
scope of this tutorial, it is worthwhile to mention some of the details.
First there are some alternatives but they are not as good as an actual blue
box. Many computers are capable of generating MF tones. Thus, your local
phriendly software pirate should have a program compatible for your computer.
However, it is highly advisable not to box from home as stated in The Ten
Commandments (as interpreted for phreaks by Fred Steinbeck -- TAP #86).
I. Box thou not over thine home telephone wires, for those who doest must
surely bring the full wrath of the Chief Special Agent down upon thy
Another alternative that has a moderate success rate involves recording the
tones from a phriend with a box or computer onto a cassette tape. They can
then be used at a fortress.
As for actual construction techniques, TAP has devoted many issues to blue
boxing. Basically, a blue box is merely a device capable of generating two
different tones simultaneously. There are two basic construction methods that I
will outline below for the electronics hobbyist.
The first involves the use of two 555 timer chips (or a 556 -- i.e., two 555's
in one chip). It offers excellent frequency and voltage stability. Also, it
does not need a diode matrix keypad but used double- pole switches instead.
Schematics for this type of box can be found in TAP issue #29.
The other common box makes use of two Intersil 8038CC Function Generators. It
also requires a diode matrix keypad, potentiometers, an LM-100 voltage
regulator, a 741 Op-amp, and a handful of other parts. The schematics for this
type of blue box can be found in TAP #26.
Both designs draw about 20 ma of current.
Also, most blue boxes use telephone earpieces (with the varistor removed) for
speakers. These can be easily liberated from fortress fones with a small
Usually, the hardest part about building a blue box is the calibration. A
frequency counter is a must and an oscilloscope won't hurt.
Some boxes also take timing into account. It is feasible on the ESS systems
that they check to see if the digits are of uniform length. If they aren't,
they are probably from a blue box and a trouble card may be dropped. With this
in mind, the Bell standard for MF pulses and interdigit intervals is around 75
ms. It varies with the equipment used since ESS can handle higher speeds and
doesn't need interdigit intervals.
Besides dialing normal calls free, i.e., KP+NPA+NNX+XXXX+ST, blue boxes offer
the entire network for exploration. Emergency break-ins, service monitoring
(aka taps), stacking tandems (the art of busying out all trunks between two
points), re-routing calls, conference calls, and much, much more are all
feasible. Although, Bell frequently changes these codes due to phreaks.
Here are some standard ones, though:
OPERATOR & OTHER CODES:
(an optional NPA may proceed all of the numbers; otherwise, you will reach the
one local for the area where the call is originated)
001 -- Trunk Access System
009 -- Rate Quote System
101 -- toll office test board
121 -- INWARD Operator
This operator assists the local "0" operator in completing calls. (S)he will
dovirtually anything for you providing it is within her NPA.
131 -- Operator Directory
141 -- Rout & Rate
(141 defunct -- use KP + 800 + 141 + 1212 + ST)
These operators are very useful if you know how to mumble a few cryptic phrases
as compiled below (with thanks to Fred Steinbeck):
To find out...
For example say , "Miami, Florida, numbers route, please." The R&R operator
will tell you "305 plus," meaning that 305 plus the seven digit number will get
... Inward Operator City Codes
Usually, the INWARD operator for an area is simply KP + NPA + 121 + ST. In
somearea codes, though, there are several large cities and thus several
inwards. Tofind the inward for a specific city, you would say "916 756,
please" to the R&R operator who will then tell you "916 plus 001 plus." This
means that KP+ 916 + 001 + 121 + ST will get you an inward for Sacramento, CA
... City names
If you want to know the city that corresponds to an area code and exchange, you
simply tell the R&R, "Place name, 914 390, please." In this example, the R&R
operator will respond with "White Plains, NY."
... International Directory Assistance
If you need a directory route for London, you could say "International, London,
England. TSPS directory route, please." The R&R operator will respond with
"Directory to London, England. Country code 44 plus 1 plus 986 plus 3611."
Therefore to get a DA operator in London, you would route yourself to an
international sender and KP + 04419863611 + ST.
... Country & City codes
If you need to know the country and city code for an international number you
can say "International, Sydney, Australia, TSPS numbers route, please" and get
"Country code 61 plus 2."
... International Inwards Routes
To get routing codes for international inwards say "International, London,
England, TSPS inward route, please." The R&R Operator will respond with
"Countrycode 44 plus 121."
Finally, to get language assistance for completing a foreign call you can tell
the foreign inward, "United States calling. Language assistance in completing
acall to (called party) at (called number)."
151 -- overseas incoming (212 +
160-XX0 -- Various Overseas Operators
161 -- trouble reporting operator
181 -- Coin Refund Operator
18X -- Overseas senders
To make an international call, one would KP + 011 + 0CC + ST where CC is the
country code. This will route you to the appropriate overseas sender. You will
then receive a 480 Hz dial tone. Here you enter KP + 0CC + city code + local
number + ST and the call is on its way.
Country codes can be either 1, 2, or 3 digits but they must be padded for three
digits to create a pseudo-country code with extra zero's if necessary. For
example, England, country code 44, becomes 044.
To see which international sender a certain country (lets use French Guiana,
country code 594, for example) goes through, you can dial KP + 011 + 594 + ST,
wait for the Proceed to Send tone then KP + 000 + 0000 + ST and you will
receive a recording saying which ISC (International Switching Center) it is. For
example it will say, "This is the international switching center in Pittsburg,
PA -- This is a recording - 4121." You can actually route calls to certain
senders yourself (KP + NPA + 18X + ST) but it is better off not to since it may
look suspicious if a call is sent through a sender that it shouldn't go
Here are the senders:
182 -- White Plains, NY
183 -- New York, NY
184 -- Pittsburg, PA
185 -- Orlando, FL
186 -- Oakland, CA
187 -- Denver, CO
188 -- New York, NY
Also, there tends to be alot of talk about the Code 11, Code 12, KP2, STP,
ST3P,& ST2P keys. While they do exist the blue boxer need not concern himself
them. The first three are used on CCITT System 5. This is the signaling system
that the International Senders use to send information to other countries.
These codes are usually added automatically just like the language assistance
digit [which distinguishes operator (or blue box) dialed calls from customer
dialed calls]. The STP, ST3P, & ST2P tones are used when equipment is
communicating with the TSPS. These also are automatically added when needed in
[see Telcom III for more on International Switching Centers (ISC)]
11XXX -- miscellaneous operators
11501 -- universal cordboard
11511 -- conference operator
11521 -- mobile operator
11531 -- marine operator
11541 -- LD incoming switchboard
11551 -- leave word for time &
charges (neat stuff)
11561 -- same as 11551 but for
11571 -- overseas operators --
The 11XXX series is interesting scanning material.
Miscellaneous Routing Codes :
Alliance Teleconferencing has several numbers, a few of which are listed below:
KP + 213 080 XXXX + ST
KP + 305 025 XXXX + ST
KP + 312 001 XXXX + ST
XXXX = 1050, 1100, or a few others
Also, at KP + 317 009 + ST there is a MF tone checker. After the
beep-kerclunk,dial in KP + 999 1234567 890 + ST and it will repeat the digits
that you pulsed if they are of the right frequency.
To find all sorts of interesting things, you must look. Begin scanning three
digit codes in your area (i.e., KP + 000 + ST, KP + 001 + ST, etc.). Keep track
of all of your results. Sometimes you must probe things, send additional digits
and see what happens, send touch-tone, send it 2600 Hz, rip it apart. You
neverknow, you may run into something phun, like a computer that checks CC
Incidentally, in some exchange you can dial inwards and other box codes
directly! For example, 914-121-1111 will get you a NY inward. The only problem
is that a 0 or 1 as the first digit of the exchange is usually prohibited in
customer dialing. Somebody may have "accidentally" changed this screening code
on your ESS's computer, though -- you never know and it can't hurt to try.
WATStranslation numbers also take up some of the 0XX & 1XX codes.
Finally, certain tones on the blue box can also be used for other purposes. An
MF "2" corresponds to COIN COLLECT while "KP" corresponds to COIN RETURN. Thus
every blue box is also a green box (see Telcom VI).
Telcom VIII will deal with cordless phones, mobile phones, and other neat
Be careful and have phun,
January 21, 1985
The preceding was intended for
informational purposes only. The
implementation of some of the above
mentioned information may be a
violation of state and/or federal laws.
[Sherwood Forest ][ -- (914) 359-1517]
PS All sysops are welcome to use this
material in its unadulterated form.
PPS Any and all threats, comments,
suggestions, and/or subpoenas are
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