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TUCoPS :: Phreaking Technical System Info :: mabell1.dox

How Ma Bell Works 1

Disclaimer Notice:

This file is presented as an  INFORMATIONAL file only.
Do not try any of the things mentioned in the text file
as some of them are illegal to do. The bbs operator take
NO responsibilty.
                        How Ma Bell Works

    In  this  article,  I  will first describe  the  termination, 
wiring,  and  terminal  hardware most commonly used in  the  Bell 
system, and I will include section on methods of using them.

                          LOCAL NETWORK

     The   local   telephone   network   between   the    central 
office/exchange  and  the  telephone subscribers can  be  briefly 
described as follows:

     From  the  central office (or local exchange) of  a  certain 
prefix(es), underground area trunks go to each area that has that 
prefix  (Usually  more than one prefix per area.)  At  every  few 
streets or tract areas, the underground cables surface. They then 
go to the telephone pole (or back underground,  depending on  the 
area)  and  then  to the subsribers house (or in the case  of  an 
apartment building or mutliline business,  to a splitter or  dis-
tribution box/panel). 

Now  that  we have the basics,  I'll try and go in-depth  on  the 

                       UNDERGROUND CABLES

     These  are sometimes inter-office trunks,  but usually in  a 
residential  area they are trunk lines that go to bridging  heads 
or  distribution  cases.  The cables are about 2-3  inches  thick 
(varies),  and  are  either  in  a metal  or  pvc-type  pipe  (or 
similiar).  Rarely (maybe not in some remote rural areas) are the 
cables  just 'alone' in the ground.   Instead they are usually in 
an  underground cement tunnel (resembles a small sewer or  storm-
drain.)   The manholes are >heavy< and will say 'Bell system'  on 
them.  they can be opened with a 1/2 inch wide crowbar (Hookside) 
inserted  in the top rectangular hole.  There are ladder rungs to
help you climb down.  You will see  the cable  pipes on the wall,
with the blue and white striped one being  the inter-office trunk
(at  least  in my  area).  The others  are local  lines,  and are
usually marked or color  coded.  There is almost  always a posted
color code  chart on the  wall, not to mention  Telco manuals de-
scribing the cables and terminals, so I need not get into detail.
Also, there is usually  some kind  of  test equipment,  and often
Bell test sets are  left  in there.

                         BRIDGING HEADS

     The  innocent-looking  grayish-green boxes.   These  can  be 
either trunk bridges or bridging for residences.  The major trunk 
bridging  heads  are usually larger,  and they have the  'Western 
Electric' logo at the bottom,  whereas the normal bridging  heads 
(which  may  be different in some areas-depending on the  company 
you are served by.  GTE B.H.'s look slightly different.  Also, do 
not  be  fooled by sprinkler boxes!)  They can be found  in  just 
about every city.

     To open a bridging head: if it is locked (and you're feeling 
destructive),  put a hammer or crowbar (the same one you used  on 
the  manhole) in the slot above the top hinge of the right  door.  
Pull hard, and the door will rip off. Very effective! If it isn't
locked (as usual),  take a 7/8 inch hex socket and with it,  turn
the bolt  about 1/8 of a turn  to the  right  (you  should hear a
spring release inside). Holding the bolt, turn the handle all the
way to the left and pull out.

To Check for a test-set (which are often left by Bell employees),
go inside - First check  for a test-set  (which  are  often  left 
by  Bell  employees).   There should be a panel of terminals  and 
wires.   Push the panel back about an inch or so,  and rotate the 
top  latch  (round with a flat section)  downward.   Release  the 
panel  and it will fall all the way forward.  There is usually  a 
large  amount  of wire and extra terminals.   The  test-sets  are 
often hidden here,  so don$ overlook it (Manuals,  as  well,  are 
sometimes placed in the head).   On the right door is a metal box 
of alligator clips.   Take a few (Compliments of Bell.).  On each 
door is a useful little round metal device. (Says 'insert gently' 
or'  clamp  gently - do not overtighten' etc..)  On the front  of 
the disc, you should find two terminals.  These are for your test 
set.   (If you dont have one, dont despair -I'll show you ways to 
make basic test sets later in this article).

     Hook the ring (-) wire to the 'r' terminal;  and the tip (+) 
wire  to the other.  (By the way,  an easy way to  determine  the 
correct polarity is with a 1.5v LED.   Tap it to the term.  pair, 
if  it  doesnt light,  switch the poles until it does.   When  it 
lights,find the longer of the two LED poles:  This one will be on 
the  tip wire (+).   Behind the disc is a coiled  up  cord.  This 
should have two alligator clips on it..  Its very useful, because 
you dont have to keep connecting and disconnecting the fone (test 
set) itself, and the clips work nicely.

     On  the  terminal  board,  there should be  about  10  screw 
terminals  per  side.   Follow the wires,  and you can see  which 
cable pairs are active.  Hook the clips to the terminal pair, and 
you're set!   Dial out if you want,  or just listen (If someone's 
on theline).  Later,  I'll show you a way to set up a true  'tap' 
that  will let the person dial out on his line and receive  calls 
as normal, and you can listen in the whole time.  More about this 

     On  major  prefix-area bridging heads,  you can  see  'local 
loops' ,which are two cable pairs (cable pair = ring+tip,  a fone 
line)  that are directly connected to each other on the  terminal 
board.   These  'cheap  loops' as they are called,  do  not  work 
nearLy  as  well  as the existing ones set up  in  the  switching 
hardware  at the exchange office.   (Try scanning your  prefixes' 
00xx  to 99xx #'s.)  The tone sides will announce themselves with 
the 1008 hz loop tone,  and the hang side will give no  response.  
The  first  person  should dial the 'hang' side,  and  the  other 
person dial the tone side,  and the tone should stop if you  have 
got the right loop.)

     If  you want to find the number of the line that you're  on, 
you  can either try to decipher the 'bridging log' (or whatever), 
which is on the left door.  If that doesnt work,  you can use the 

                   ANI # (Automatic Number ID)

     This  is a Telco test number that reports to you the  number 
that youre calling from (It's the same, choppy 'Bell bitch' voice 
that you get when you reach a disconnected #) 

For the   213 NPA - Dial 1223
          408 NPA - Dial 760
          914 NPA - Dial 990

     These  are  extremely useful when messing with any  kind  of 
line terminals, house boxes, etc.

     Now that we have bridging heads wired, we can go on... (dont 
forget to close and latch the box after all... Wouldnt want to GE 
and Telco people mad, now,would we?) 

Continued in: Ma Bell part II

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