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
understood.
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.
HISTORY
-------
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
switching.
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
----
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.
EXAMPLES OF LAMA USAGE
----------------------
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
article.
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.
ANI FORMATS
-----------
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
line
1MR Single party Metered rate residential
line
1CF Single party Coin First coin
telephone
1OF Single party Official (telco) line
1FB Single party Flat rate Business line
1MB Single party Metered rate Business
line
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
----
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
areas