Visit our newest sister site!
Hundreds of free aircraft flight manuals
Civilian • Historical • Military • Declassified • FREE!


TUCoPS :: Phreaking Technical System Info :: dacs.txt

Digital Access Carrier System (DACS)




BL4CKM1LK teleph0nics [ http://hybrid.dtmf.org ]
Digital Access Carrier System DACS
by hybrid <hybrid@dtmf.org>



How did I get this info? -- Well the truth is, as a young child I was
abducted by extra terrestrial biological entitys who hardwired microchips in
my brain that allow me to intercept the thoughts of telecommunications
engineers via ESP.. I was told to gather intricate information about the
planet Earth's international PSTN, so when my people from the distant world
of xinbin come to inhabit the planet, they can use the information I have
transmitted to them from the microchips in my brain as a means to take over
our communication networks... er, shit, thats not rite (better lay off the
caffiene for a bit).. What I ment to say was, a friend of mine werks for BT,
and gave me some nice info on DACS :) -werd


Introduction.


Digital Access Carrier System is used by British Telecom to transform one
residential line into two seperate lines without actually installing an
additional trunk pair. The idea of DACS is very similar to the design and
implementation of the WB9OO unit used in the past (http://hybrid.dtmf.org/
files/hybrid-files/wb900.txt). The DACS system is becomming increasingly
popluar in the UK beacuse more and more people are requesting additional
lines, usually for net access.


        Digital Access Carrier System


                _____________                    _____________
    B1         |             |                  |             |        B1
  -------------O             | single pair of   |             O-------------
               |             | wires (trunk)    |             |
    analogue   |     E.U     O==================O     E.U     |   analogue
               |             | digital          |             |
  -------------O             |                  |             O-------------
    B2         |_____________|                  |_____________|        B2




The chances are, if you order another line from BT, they will simply
multiplex your existing line into 2 seperate carriers. Think about it.. if
you have one line operating on a dedicated carrier, then the line is
multiplexed into 2 serperate carriers, the bandwith will be cut in half. To
this date, BT are encouraging its customers to join the 'BT SuperHighway' by
installing a second line.. What BT dont tell you is that you will only be
able to get a maximum of 28.8bps from your 'second' line.

In this file, I'll look into the DACS carrier system in detail, aswell as
ways to determine what kind of trunk installation you have if you have
ordered a second line from BT. Werd, enjoy the file..


DACS II


The origional DACS system had limited capabilitys, and did not allow the
customer to have CLASS services on their line. The newer DACS implementation
is called DACS II and allows a slightly more advanced service to customers.
Now people with DACSII units on their line, have access to CLASS (Customer
Loop Access Signalling System). The new DACS hardware, allows customers lines
to have K Break (Disconnect Clear), aswell as common services such as CLI,
which where previously unavailable to DACS I customers.


At the eXchange


All exchanges have a database of different customers who have been fitted
with the DACS equipment. Some of the commands used on the CSS database at
the local terminating exchange are as follows:

        <DFTR> DISPLAY FRAME TERMINATION RANGE (to see if DACS equipment is
                                                fitted to the exchange)

        <DFJ> DISPLAY FRAME JUMPER (to determine whether a particular
                                    customer is using DACS1 or DACS2)

Remote End eXchange records


The Local Network Records (CSS/LNR) are modified/editited as follows on the
O/S at the exchange:

        <ESU> ENTER SHARED USE
        <MSU> MODIFY SHARED USE
        <DRT> DISPLAY ROUTING
        <HEH> INVALID COMMAND

Compatability of DACS:

GOOD..

The provision of PSTN services when used with only BABT - approved Customer
Premises Equipment upto 4 REN.

Use of any phone exchange within BT's access network, except the following:

        Inter working with all BT's remote line test systems
        Self contained payphones
        Lines utilising CLASS
        K Break
        All modems up to 14.4bit/S working
        Group 1,2,3 fax machines
        Video phones

BAD..

Earth calling PBX's
Equipment that uses SPM (meter pulsed payphones)
Private Services
ISDN2
Steel joint user poles
Certain TXE2 exchanges
300 kilohms loop calling
Electricity stations
DDI
Group 4 fax machines



DACS system schematics, diagrams..


        Old Jumpering Procedure


                               E             L
                               :             :
                _____________  :             :   _____________
               |             | :             :  |             |
               |             O-:-----.     .-:--O             |
    exchange   |             O-:---. |     | :  |             | external
  <------------O sub number  | :   | |     | :  |  bar pair   O------------>
               |             | :   | |     | :  |             | cable
               |             | :   | |     | :  |             |
               |_____________| :   | |     | :  |_____________|
                               :   | |     | :                              
                               :   | |     | :
                               :   | |     | :   _____________
                               :   | |     | :  |             |
                               :   | |     | :  | DACS block  |
                               :   | |     | :  |             | DACS shelf
                               :   | |     | :  |             O------------>
                               :   | |     | :  |             |
                               :   | |     | :  | T  B1   B2  |
                               :   | |     | :  |_____________|
                               :   | |     | :     o  o    o
                                   | |     |_______|  |    |
                                   | |________________|    |
                                   |_______________________|



        New Jumpering Procedure

                                 E          L
                                 :          :
                _____________    :          :    _____________
               |             |   :          :   |             |
               |             |   :          :   | DACS B1 B2  |
    exchange   |             |   :          :   |             | DACS shelf
  <------------O sub number  |   :          :   |             O------------>
               |             O---:----------:---|--O B2       |
               |             O---:----------:---|--O B1       |
               |_____________|   :          :   |_____________|
                                 :          :
                                 :          :
                                 :          :
                _____________    :          :    _____________
               |             |   :          :   |             |
               | DACS trunk  |   :          :   |             |
    DACS shelf |             |   :          :   |             | external
  <------------O             |   :          :   |  bar pair   O------------>
               | CH2         |   :          :   |             | cable
               | CH1      O--O---:----------:---O             |
               |_____________|   :          :   |_____________|
                                 :          :
                                 :          :
 
        E.U Card Setup


    
                      _________________________________________            
  .--------.         |             (O) (O) (O)                 |           
  |        |         |      |   |   |   |   |   |   |   |  on  |           
  |        |       1 |      |   |   |   |   |   |   |   |  off | 8          
  |        |         |_____(O)_(O)_____________(O)_(O)_(O)_____|           
  |        |                                                               
  |        |                                                               
  |        | <-- B.E.R connector                                                             
  |________|                                                               
                 sw7O9      sw7O3      sw7O6      sw7OO                                         
                 _____      _____      _____      _____                    
              c |     |  c |     |  c |     |  c |     |          .--------.
                |  :  |    |  :  |    |  :  |    |  :  |          |        |
                |  :  |    |  :  |    |  :  |    |  :  |          |        |
                |  :  |    |  :  |    |  :  |    |  :  |          |        |
                |  :  |    |  :  |    |  :  |    |  :  |          |        |
              r |_____|  r |_____|  r |_____|  r |_____|          |        |
                  b2         b1         a3         a1             |        |
                                                                  |________|



        DACS 2A EU
        SW 1O1
                     (imp)                              (class)
  _____    _____    _____    _____         _____    _____    _____    _____
 |     |  |     |  |     |  |     | cpx   |     |  |     |  |     |  |     |
 |  O  |  |  O  |  |  O  |  |  O  | 6OO   |  O  |  |  O  |  |  O  |  |  O  |
 |     |  |     |  |     |  |     |       |     |  |     |  |     |  |     |
 |     |  |     |  |     |  |     |       |     |  |     |  |     |  |     |
 |     |  |     |  |     |  |     |    en |     |  |     |  |     |  |     |
 |_____|  |_____|  |_____|  |_____|       |_____|  |_____|  |_____|  |_____|      
    
    1        2        3        4             1        2        3        4


    1   SW 1O2                 4
  _____    _____    _____    _____
 | off |  |     |  |     |  |     |      
 |     |  |     |  |  O  |  |  O  | 1Ok     
 |     |  | on  |  |     |  |     |      
 |     |  |     |  |     |  |     |      
 |  O  |  |  O  |  |     |  |     | 15k      
 |_____|  |_____|  |_____|  |_____|             

    1        2        1        2

     (alarm)            (sign)



        External RU Setup
        BT66


            white
      B1  O--------------.
            blue         |    white
                         | .-------------.
                         | |  grey       |
                         | |             |
                         | |             |
                         | |             |
                         | |             |
                         | |             |
            white        | |             |
      B2  O------------. | |             |
            orange     | | |             |
                       | | |             |
                       | | |             |
                       O O O             |
                                         |
                       tail              |  trunk
                                         O

        MIMIC Resistances

                                               switch 5 on (cal)
                                               1k ohm loop
                   _____                        _____
                  |     |                      |     |             
 C        a       |     |                      |     |         a   ______
 S       o--------O     |  switch 5 off (ug)   |     O------------O      |
 S           b1   |     |  10k ohm -50v leg b2 |     |  b1        | NTE  |
         o--------O     |                      |     O------------O______|      
 T        b       |     |                      |     |         b 
 E                |     O======================O     |
 S                | EU  O======================O RU  |
 T        a       |     |        TRUNK         |     |         a   ______
         o--------O     |                      |     O------------O      |
 A           b2   |     |                      |     |  b2        | NTE  |
 C       o--------O     |                      |     O------------O______|
 C        b       |     |                      |     |         b
 E                |_____|                      |_____|
 S
 S       s/c b1 + b2       10k ohm -50v a leg b2    1k ohm loop b1 or b2
         EU fault          TRUNK fault               customer apps fault



Welp, thats it for this DACS oday info. Hope someone can find some use of it,
HEH. Big shouts to gr1p, b4b0, 9x, substance, psyclone & GBH krew, tip, jorge,
lusta, pbxphreak, bodie, zomba, jasun, oclet, knight, epoc, nou, everyone in
#darkcyde, #b4b0, #9x HEH, werd to D4RKCYDE.. 2 years going str0ng.

"that ascii took me fuckin ages.."

the urls..

http://b4b0.org                 b4b0
http://darkcyde.phunc.com       f41th
http://www.ninex.com            9x
http://hybrid.dtmf.org          BL4CKM1LK hardcore teleph0n1cs.. (GO NOW!)

ATE/>exit
+++
NO CARRIER



TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2014 AOH