                      THE THEORY OF "BLUE BOXING"                

                After most neophyte phreaks overcome their
fascination with Metrocodes 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 principales
of the fine art of blue boxing.                                  
                               GENESIS  
              In the begining, all long distance calls were
connected manually by oper-ators 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. 
Since long distance calls require routing through various switch-
ing 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 options:                               
   (1) to send all the signaling and supervisory information (ie.
      ON and  OFF HOOK) over separate data links.   This type of 
     signaling is referred to as out-of-bandsignaling,
                          or
   (2) 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 signaling. 
                                                                 
         Beingthe cheap bastards that they naturally are, Bell
chose the latter(and cheaper) method - in-band signaling.  They
eventually regretted this, though (heh,heh)...                   
                                                                 
    IN BAND SIGNALING PRINCIPLES                              
When a subscriber dials a telephone number, whether in rotary or
touch-  tone (aka DTFM), 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) 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
circuts are busy...'message.  If it does find a free trunk, it
'seizes' it --removing the 2600Hz.

  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 touchtones. 
            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.   
                        HISTORY                                  
               In 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:


              DIGIT TONES                                        
            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
inter-national 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.
   These units were 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.  Surprisinglyenough, blue boxing is not solely
limited to the electronics enthusiast:  
   AT&T has caught businessmen, film stars, college students,    
doctors, lawyers, high school students, and even a millionaire
financier (Bernard Cornfield)  using the device. AT&T also
said that nearly half of those that they catch are businessman.
