The LOD/H Technical Journal, Issue #3: File 02 of 11


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           O           AUTOMATIC MESSAGE ACCOUNTING            O

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           $                       (AMA)                       $

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           O                    An overview                    O

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           $            Written by Phantom Phreaker            $

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           O                  Legion Of Doom!                  O

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    This article is meant to provide an explanation of Automatic Message

Accounting (AMA) and how it was/is used in the past and present.

    All information included in this file is correct to my knowledge, however,

if anyone notices any errors or has anything interesting to add, try to get in

touch with me one way or another and let me know.

    Hopefully this article will clear up any misconceptions about AMA that

have been circulating around on bulletin boards and by word of mouth. Keep in

mind, however, that the information here may not be applicable to your

specific area or telco. The information contained herein generally applies to

the BOC's, and if you are served by an independent telco, your method of

billing may differ.

    This article is aimed more towards the more experienced telecommunications

enthusiast. People with limited knowledge may have a hard time understanding

the information presented here. However, if you can contact me I will try to

answer any questions or clarify anything included in this article that isn't


    Information will be included in this article concerning the use of AMA in

the past. This is being done for people in older areas or areas served by an

independent telco that may still be using the old technology.



    In the past, Call Detail Record (CDR) information was collected and

recorded by cordboard operators in a process known as manual ticketing. The

operator recorded this information by writing it down manually upon a

formatted record called a ticket. These tickets were sent to the appropriate

office where billing was handled. This manual ticketing process was

time-consuming, and was phased out with the introduction of electromechanical


    Before the advent of AMA, a magnetically operated counter called a message

register was associated with each subscribers line in a given central office.

This counter was responsible for counting the number of calls that each

subscriber made, for billing purposes. This message register was caused to

operate one or more times when the called party answered the telephone. The

way this works is when the called party answers, a reverse battery signal was

sent back over the trunk circuit to activate a relay in the originating office

which was responsible for the application of a 48-volt battery to advance the

message register the appropriate number of units. A local call is/was usually

one message unit, regardless of how long the call lasted.  Local calls to

further away areas were/are usually two message units.  Long distance calls

were handled either by cordboard operators, using manual ticketing, or by a

method not involving operators known as zone registration. With zone

registration, calls to different zones would cause the message register to

operate two or more times per time period. This would make the cost higher for

longer calls, and less for shorter calls.

    At the end of the billing period, each message register had to be manually

photographed to keep track of the number of calls made by that specific

subscriber. These photos were taken by a 35 millimeter camera that was known

as a Traffic Usage Recorder, and then sent to the same place that manual

tickets (prepared by operators) were.  However, this method of billing soon

grew costly and inefficient, so a new method, LAMA (Local Automatic Message

Accounting) was developed. Additional and more specific information shall be

included later in the article.

    In the late 1940's, the Bell System developed LAMA, which recorded the

billing information in a much more efficient manner. However, some end offices

did not have enough call traffic to warrant the installation of LAMA

equipment.  To solve this problem, CAMA (Centralized Automatic Message

Accounting) was developed in the mid 1950's. CAMA was different from LAMA in

that it was based in a toll or tandem office and could record the AMA

information for every end office that it served. More on LAMA and CAMA will be

included later in the article.

    Another development concerning AMA is the computerization of the system,

named LAMA-C or CAMA-C, for 'LAMA-Computerized' or 'CAMA-Computerized'. CAMA

had used paper tape perforators for a time before the magnetic tape method was

introduced with CAMA-C. LAMA-C is a computerized version of LAMA which also

uses magnetic tape (LAMA-C is still used today). LAMA and LAMA-A (previous

versions) used paper tape, although LAMA-A was more efficient.

    LAMA, LAMA-A, CAMA, and CAMA-C were all part of the AMARS, the Automatic

Message Accounting Recording System. However, a newer term for more modern

setups is the AMACS, for Automatic Message Accounting Collection System. The

AMACS includes end office AMA systems, a recent introduction called the AMARC

(AMA Recording Center), AMARC sensors from end offices to the AMARC, the data

links used to transmit billing information, and data recievers located at the

AMARC site. The AMARC is a product of the new age of computerized technology

as it applies to the telecommunications systems used in our society.  Still,

LAMA and CAMA and their different versions shall be described and explained to

help people understand how they were/are used.



    LAMA is described by Notes on the Network (1983) as 'A process using

equipment located in a local office for automatically recording billing data

for message rate calls and for customer-dialed station to station toll

calls'.  What this is means is that if your CO uses LAMA, and you are on a

single party line (most people are), all 1+ toll calls will be billable by

LAMA equipment, and all calls coming from message rate lines. A message rate

line, for those of you not familiar with the term, is a telephone line that

has the ability to receive incoming calls, but all outgoing calls will cost

the subscriber. The subscriber pays for basic service (the ability to receive

calls) with the consideration that all other calls (even local ones) will cost

a certain amount of money per call. Many subscribers in several major cities

get this feature automatically, and thus phone bills are generally higher in

these areas.

    LAMA originally recorded billing information on punched paper tape, in a

version known as LAMA-A, but now magnetic tape is generally the format used in

places where LAMA-C equipment is used.  The paper tape perforators that

recorded the CDR data in LAMA-A were noisy, and they needed maintenance due to

their electromechanical construction. The magnetic tape method is much more

reliable, and quieter as well.

    If a persons End Office uses LAMA, then all toll calls from all lines and

all local calls from metered rate lines are recorded on the LAMA tape, with a

few exceptions. LAMA can only be used to record AMA information for one and

two party lines. On other party lines such as three and four party, the

originating caller has his/her number identified by an operator via the ONI

(Operator Number Identification) method. It is not been determined by the

author if the BOC (Bell Operating Company) operators such as TOPS (Traffic

Operator Position System, made by Northen Telecom Inc. of Canada) or MPOW

(Multi-Purpose Operator Workstation, by US West) operators would be used for

this ONI or not. I would guess that AT&T TSPS operators would handle an

inter-LATA toll call, and that the BOC TOPS/MPOW operators would handle the

ONI for an intra-LATA call (my reasoning behind this statement is the fact

that whenever I have had an ONI due to equipment failure, which is similar to

ONI needed, only the ANI outpulsing was garbled, the called number was still

transmitted in the correct fashion.  I am assuming that the end office

switching system would route the call to the correct operator position by

matching the NPA-NXX with some sort of internal table which makes a

distinction between intra and inter-LATA calls). Anyway, these calls had their

AMA information sent from the appropriate operator position to the toll office

that served the 3+ party line, onto CAMA tape.  Another instance in which a

LAMA office may use CAMA instead is when an ANIF (ANI Failure) occurs. If the

ANIF is sent to TSPS, then that TSPS will record billing information upon CAMA

tape by using ONI. It seems that AMA information that has been recorded by an

operator is buffered and stored until it is time to send the information to

the appropriate places for processing. In the case of AT&T TSPS operators, the

TSPS had it's own magnetic tape which was sent to the RAO (Regional Accounting

Office, formerly called Revenue Accounting Office) on a regular basis. I am

not sure if this method is still used or if TSPS AMA has been updated or

enhanced in some way.



    The following is the call flow procedure in a LAMA-A (paper tape) system.

    After a customer completes dialing, the dialed number (the called number),

the originating class of service, Line Equipment Number (LEN), and call type

are sent from the switch to the AMA equipment.  Translations, such as figuring

the billing telephone number from the Line Equipment Number, are done. The

information that comes from the translations procedures determines which paper

tape perforator shall be used to record the data for this specific call. A

record of the initial information gathered is called the initial entry. The

last line of the initial entry contains a two digit code called a Call

Identity Index, which identifies telco equipment such as the trunk or district

junctor that will be used for that call.

    When the call is answered, another entry is made, called the answer

entry.  This entry is a single line on the paper tape and has the CII and the

exact time that the call was answered on it.

    The last entry on the paper tape is known as the disconnect entry.  This

entry contains the CII and the exact time that the call ended.

    The CII is important because it is what the RAO used to group together all

the data about a given call. Entries are recorded at different times in a LAMA

system, they are not in sequential order, so the CII makes it easier to find

all three entries for a specific call.

    This method of recording AMA information required the RAO to 'unshuffle

the deck' when it came time to organize the AMA information. The variations in

the AMA recording formats used by different switching systems eventually led

Bellcore to develop a standard AMA format, named the Bellcore AMA Format

(BAF).  More information will be included about this format later in the


    In a No. 5 Crossbar switching system, the AMA setup used special purpose 3

inch wide paper tape on which AMA records were recorded by CO equipment. This

method of recording is for the stone ages, as it has been phased out by almost

every BOC. Similar to the LAMA-A call flow, this method of AMA used three AMA

entries. The first one was the customers service information, which included

the calling and called telephone numbers, the second one was recorded when the

telephone was answered, and the third one was recorded at disconnect.  This

also made the job at the RAO a bit harder, as again, they had to 'unshuffle

the deck'.

    The No. 2 ESS introduced the latest magnetic tape recording technology

that was available at that time. The 2E used 200 BPI, 7 track mag tapes, and

it introduced special data coding conventions.  It's technology and

conventions are still in use today, but I think that the BPI and number of

tracks have been increased. The 2E mimics the No. 5 Crossbar AMA method by

recording three entries and interleaving them on the magnetic tape. Data

common to all calls on a tape (such as date, CO info, etc.) are recorded in

special tape headers. The No. 2B ESS was introduced with the same AMA

technology as the 2E, but a 2B that provides equal access capabilities for

interexchange carriers adds a new data entry to the three used by the 2E. This

new entry reports the time of connection of a carrier to the local network,

which is needed for carrier access billing.

    The No. 1 ESS modernized the AMA process even more. The 1E used 200 BPI,

nine track tape. The 1E provides data collection memory registers for AMA

information on applicable calls. A register is assigned to an AMA call and

kept open for the call's duration. This register collected most of the billing

data that was needed. The AMA information was then written to magtape at the

time of disconnect.  This made it easier for the RAO to process. The AMA

format used by the 1E uses variable length records whose fields occur for the

most part in a general, preset pattern. Eventually, though, even the 1E AMA

method was found to be slightly faulty. This was due to high processing costs

at the RAO and the problem of tape headers getting erased from the tape. The

BAF was made to solve the problems that are associated with other AMA setups.

An update to the BAF is called the EBAF, or Extended Bellcore AMA Format. The

main difference between the BAF and EBAF is that EBAF is more flexible and can

be used easier, as the BAF uses a defined structure for storing data. The EBAF

can append other information to the end of an AMA record, and this makes it

more flexible.



    The ANI formats outpulsed in a LAMA arrangement are as follows (assume

that the call being shown for an example is being dialed from a home

telephone, as dialing from coinphones would cause different ST signals to be

sent; also the type of signaling in this case is SF in-band):

                      CALLED number:KP+(NPA)+NXX+XXXX+ST

                       CALLING number:KP+I+NXX+XXXX+ST

    The second format is the ANI associated with LAMA and is sent to the LAMA

equipment after the ANI receiving trunk winks. The NPA included in this

example is optional and only needed if the subscriber is making a call to a

Foreign NPA (FNPA). The complete called number is not included in all cases,

as when an AMA setup is configured for bulk-billing. In bulk-billing, the

entire called number is not recorded, but just enough for billing purposes.

The CALLING number is the number that the subscriber is dialing from.  These

two numbers are sent in Multi Frequency (MF) tones to MF receivers located

within a CO. The I in the ANI is an information digit, and these shall be

explained later in the article.

    One may wonder how a CO knows which lines it serves are message rate lines

and which are flat rate. On electromechanical switches such as Step by Step,

No. 1 and No. 5 Crossbar (it should be noted that there are no remaining panel

switches within the Bell System), there is an electronic line card associated

with each Directory Number which holds information relevant to that line.

These cards have to have any type of change hardwired into them. However, in

digital/ electronic switching systems, there are Line Class Codes which

reflect information about each subscribers line. There are many, many of these

codes.  Some of the more common and interesting ones are listed below:

    LCC                                          EXPLANATION

    ---                                          -----------

    1FR                         Single party Flat rate Residential


    1MR                         Single party Metered rate residential


    1CF                         Single party Coin First coin


    1OF                         Single party Official (telco) line

    1FB                         Single party Flat rate Business line

    1MB                         Single party Metered rate Business


    These codes can be found for a line in several places, such as certain

fields in telco computer output reports. COSMOS and LMOS are two such

computers that hold this information. If you find COSMOS printouts or have

access to COSMOS, these Line Class Codes will be listed under the 'LCC' field

in an ISH, INQ, or other inquiry.  Sometimes the data in the LCC field will

match or be similar to the data in the US field, which is a USOC (Universal

Service Order Code).  A USOC and an LCC aren't the same thing though.



    CAMA operates along the same basic principle that LAMA does, except that

CAMA is based in a toll or tandem office (class 4). CAMA is made to be used in