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

About ACTS

I receved the following documment from a friend who was then a TSPS
operator, one year ago -- just before LA cut over to the ACTS/SSAS
system.  In light of some recent discussion over automated coin
telephone service, and automatic calling card service as well, I am
submitting it to the list.


	-	-	-	-	-	-	-	-
                  Automated Coin Toll Service handles
     the routine aspects of coin-paid toll calls, freeing operators
            to deal with more complex customer interactions.

   By James O. Hardy, Dattatraya G. Raj-karne, and Kenneth A. Raschke

  "Sixty cents, please. Please  deposit 60 cents  for the first  three
minutes".  The message is familiar,  the voice is invariably  pleasant
and cheerful.  What you may not know, however, is that the  "operator"
at the other end is  not human-- it's a  machine.  By taking over  the
routine tasks associated with handling  coin toll calls, this  machine
frees operators to concentrate on more complex calls, such as  collect
or third party  billing, and  to help  any customers  who may  require

  Automated Coin Toll Service (ACTS) is the feature that makes it  all
possible.  ACTS  automatically computes  charges on  coin toll  calls,
announces charges to the customer,  counts coin deposits, and sets  up
coin calls--all without the need for an operator.

  ACTS was  developed  for  use  with  the  Traffic  Service  Position
System--an "electronic switchboard" that, since 1969, has been helping
operators handle toll and other calls requiring assistance. Today, The
Traffic  Service  Position  System--known  as  TSPS--serves  about  90
percent of  the  Bell System's  coin-paid  toll calls  on  an  average
business  day.   Automated  Coin  Toll  Service  works  with  TSPS  to
eliminate or reduce operator tasks on many of the coin-paid calls.

  ACTS can also make announcements for some non-coin operator-assisted
calls.  For  instance,  when  a  customer  requests  time  and  charge
quotations, the operator indicates this to the TSPS processor; then at
the end  of the  call, TSPS  instructs ACTS  to make  the  appropriate
announcement--for example, "The charges are three dollars and 30 cents
plus tax for seven minutes". Also,  if a customer asks to be  notified
after a specified amount  of time, the  operator inputs the  specified
time to the TSPS processor. Then, at the correct time, TSPS  instructs
ACTS to make an announcement, such as "Six minutes has ended".

  When a customer  makes a  station-to-station toll call  from a  coin
telephone, the local central office routes the call to its  associated
TSPS. In areas served by Automated Coin Toll Service, the TSPS central
processor connects the call to the Station Signaling and  Announcement
Subsystem (SSAS) hardware that  provides Automated Coin Toll  Service.
SSAS is an "intelligent peripheral" subsystem, receiving  instructions
from and sending data to the TSPS central processor.

                            SSAS TAKES OVER

  TSPS provides information to SSAS about call charges and the  length
of the  initial period  for  the call.  Using this  information,  SSAS
constructs and sends a  series of announcements  to the customer.  The
first gives The initial charge for the call.  The customer might hear,
for example, "One dollar and 20 cents please [two second pause] please
deposit one dollar and 20 cents for the first three minutes".

  If the  customer deposits  a coin  during the  initial request,  the
announcement is  truncated immediately.   This announcement  allows  a
customer to  deposit  the required  amount  without listening  to  the
entire deposit request.  As the customer deposits money, SSAS  detects
each coin signal, and totals  the amount deposited.  When the  correct
amount has  been  deposited,  SSAS  returns  control  to  TSPS,  which
completes the call  connection.  If  the customer  deposits too  much,
SSAS tells the customer that  the additional money is credited  toward
overtime.  Should the customer fail  to deposit enough money within  a
reasonable time, SSAS generates a prompting announcement.  If no money
is deposited after the prompting  announcement, TSPS adds an  operator
to the connection.  A customer can also reach an operator by  flashing
the switchhook.

  If the customer is still using the  phone at the end of the  initial
period-- usually three minutes--TSPS again connects SSAS to the  call,
and orders it to tell the customer that the initial period has  ended.
If the customer  talks beyond the  initial period and  then hangs  up,
TSPS rings back. When  the customer picks up,  TSPS instructs SSAS  to
request overtime  charges,  and  to  monitor  coin  deposits.  If  the
customer talks  for  a  long  time  after  the  initial  period,  TSPS
periodically instructs SSAS to request and collect interim deposits as

  In short, with Automated Coin Toll Service, SSAS performs two  major
functions previously requiring operators: It provides announcements to
the  customer,  and  it  monitors  coin  deposits.  To  provide  these
functions, SSAS relies on three principal components: a number of Coin
Detection and Announcement  circuits to connect  customers to SSAS;  a
control unit to  coordinate the  sending of voice  signals over  those
circuits and to interface with  the TSPS processor; and a  solid-state
announcement store to hold digitized voice signals.

                             Sample dialog

        Customer                                ACTS/TSPS
Picks up handset                        Dial-tone (from local office)

Dials number                            "One dollar and 20 cents
                                        please. [pause] Please
                                        deposit one dollar and
                                        20 cents for the first
                                        three minutes".

Deposits $1.10. Drops dime              "Please deposit 10 cents
on floor and searches for               more".
six seconds.

Gives up search and                     "Thank you. You have 15
deposits quarter.                       cents credit toward

Talks for three minutes.                "Three minutes has ended.
                                        Please signal when

Talks for two more                      Ringback of calling phone.
minutes and hangs up.

Picks up handset.                       "Twenty-five cents please.
                                        [pause] You have 15 cents
                                        credit. Please deposit
                                        25 cents more for the
                                        past two minutes".

Deposits 25 cents.                      "Thank you".

Hangs up.


  Coin Detection  and Announcement  (CDA)  circuits provide  the  link
between the customer at the coin station, and the control unit of  the
Station Signalling and Announcement  Subsystem.  Each CDA circuit  can
convert digitized speech from the announcement store into analog voice
announcements. In addition, each CDA circuit contains a data  receiver
to  detect  coin-deposit  signals  generated  by  the  coin   station;
different signals distinguish nickel, dime and quarter deposits.

  An individual  CDA circuit  handles just  one call  at a  time.  The
number of CDA  circuits needed to  handle coin toll  calls for a  TSPS
office can  therefore  vary  widely  from  one  location  to  another.
Presently,  each  SSAS  can  handle  a  maximum  of  239  announcement
circuits. Normally, though, only 30 to 100 CDA circuits are needed  to
handle coin toll  traffic, even  in large  metropolitan offices.   The
additional circuit  capacity is  available for  use in  the future  to
provide new automated TSPS services.

                         MICROPROCESSOR CONTROL

  The  SSAS  control   unit  contains  its   own  microprocessor,   or
programmable  controller--the   "intelligent"  part   of  SSAS.    The
programmable controller handles  the internal control-unit  operations
and, together with other circuitry, transfers voice data bits from the
announcement store to the CDA circuits, and communicates with the TSPS
processor.  Because  of its  central  role in  the control  unit,  the
programmable controller has several self-checking capabilities.   Some
functions within the controller are duplicated, so that errors can  be
detected by comparing the controller  outputs.  The control unit  also
checks for errors  in the  program instructions  by examining  special
binary digits  called "parity  bits"  at the  end  of each  "word"  of
instruction. Wherever  a programmable  controller error  is  detected,
TSPS is notified so that the appropriate fault recovery actions can be

  When a customer starts to  make a coin-station call, TSPS  instructs
the control unit to make an initial announcement to the customer  over
a  specified  CDA  circuit.  TSPS  provides  the  control  unit   with
information about the required deposit  and the length of the  initial
call period.  Using this information, the control unit determines  the
appropriate announcement, and  begins to  retrieve, sequentially,  the
required data  from the  announcement store.   The announcement  store
data are converted into a digital serial bit stream and transmitted to
the specified CDA circuit.  Here, the serial  bit stream is  converted
into an analog signal,  and the resulting  announcement routed to  the

  As the customer  deposits coins  in response  to announcements,  the
control  unit   interrogates   the  CDA   circuit   for   coin-deposit
information.  The control  unit totals the  coins deposited and,  when
the amount paid matches the amount required, acknowledges the  correct
deposit with  a  "Thank  you".  When  appropriate,  the  control  unit
initiates an announcement requesting additional money or  acknowledges
credit for overdeposits.  Finally, the control unit notifies TSPS when
the deposit is satisfactory--or, if the customer has not deposited the
coins quickly  enough, that  TSPS should  connect the  customer to  an

  To ensure that ACTS  will serve customers  most effectively, and  to
encourage customers to deposit coins  promptly and accurately, a  good
deal of  attention  has  been  directed  toward  the  customer-machine
interaction.  Announcements  must be  intelligible, carefully  worded,
and appropriately timed.  So a  human factors study  was conducted  in
1975 with  the cooperation  of Illinois  Bell in  Chicago, to  aid  in
determining  an  efficient  set  of  phrases,  sentences,  and  timing
parameters for the machine-generated ACTS announcements.

                            SPEECH SEGMENTS

  ACTS announcements  are constructed  from a  set of  512-millisecond
"speech segments". Each segment is equivalent to about one word of the
ACTS vocabulary.  Under the direction of the control unit,  individual
words or word segments are  retrieved from the announcement store  and
strung together  to  form  announcement phrases  and  sentences.  Most
words, such as "cents" or  "minutes" require a single speech  segment;
some words,  such as  "fifteen"  and common  phrases such  as  "Please
deposit" require two speech  segments. A few  phrases such as  "Please
signal when  through"  require  three speech  segments.   Each  phrase
involving two  or three  speech  segments could  have been  formed  by
stringing together the appropriate individual words, each encoded as a
separate 512-millisecond speech segment. More natural sounding  speech
results, however,  if  the  phrase  is  treated  as  a  complete  unit
requiring one or one-and-a-half seconds of encoded speech--that is two
or three contiguous speech segments.

  The vocabulary  of  about  80  words  presently  required  for  ACTS
announcements was initially recorded by a professional announcer.  The
words were  then digitally  encoded using  a process  called  Adaptive
Delta Modulation and organized  into eighty 512-millisecond  segments.
Each segment (word)  or group of  segments (long word  or phrase)  was
adjusted to a consistent level and pitch with silent periods  inserted
where needed.   This  results  in  natural-sounding  speech  when  the
segments  are  joined  together   in  various  combinations  to   form

  To store announcement speech  segments, SSAS uses  the same type  of
semiconductors memory  that  is currently  used  by the  TSPS  central
processor.  Each 512 millisecond  speech segment requires that  16,000
bits of  information  be stored,  grouped  into 400  individual  "data
words".  A data word  contains 47 binary digits  or bits; 40 of  these
are for announcement data, and seven for error checks.

  The announcement  store must  serve a  maximum of  239 CDA  circuits
simultaneously- even releasing the same speech segment to all circuits
at the same time if necessary. But the store is equal to the task:  It
can  release  the  data  at  the  rate  of  eight  million  bits   per
second--equivalent to 40 bits of  data every five microseconds.   This
rate ie 256  times the speed  at which digitized  speech segments  are
decoded  by  each  CDA  circuit   and  converted  to  analog   speech.
Consequently,  designers  devised  a  "time  multiplexed"  arrangement
whereby the announcement  store retrieves one  40-bit data word  every
five microseconds, and distributes  that data word to  any one of  256
circuits.  Of these, 239 are for CDA service to customers, and 17  are
for diagnostic and fault testing.

  It takes 1.28 milliseconds to distribute a data word to each of  the
256 circuits in sequence. Four hundred repetitions of the distribution
sequence release  400 40  bit data  words to  each circuit  every  512
milliseconds.   This  is  precisely  the  rate  required  to   produce
simultaneous, uninterrupted announcements, each consisting of  several
512-millisecond segments joined together.

  Although the vocabulary required for coin traffic might appear to be
constant, it  can  in  fact change.   This  is  because  call-handling
practices sometimes change,  and because any  future developments  for
Automated  Coin  Toll  Service  may  require  vocabulary  changes   or
additions.  Also a significant number of  words will be needed as  new
automated features are  added to  TSPS. The capabilities  of the  SSAS
random access  memory permit  vocabulary  changes to  be  incorporated
readily, and permit expansion of the  vocabulary to include up to  480
speech segments.


  Because Automated Coin Toll Service  must be highly reliable,  parts
of the SSAS hardware are duplicated.  Several sophisticated techniques
detect faulty operation, evaluate its seriousness, and then bypass  or
remove the faulty part from service at the most appropriate time.

  For backup in case of failure, SSAS has two identical control  units
and  announcement  stores.   One   control  unit  and  its   dedicated
announcement store constitute the "active" side and handle all  calls;
the other control unit and announcement store are called the "standby"
side.  The standby side is made active when the other side fails.

  Extensive self-checking and fault-detecting capabilities within each
side  allow  many  operations   to  occur  independently,   minimizing
interaction and common circuitry between the two sides.  Consequently,
there are very few single hardware faults that can cause both sides of
SSAS to fail simultaneously.  If such  a fault does occur, only  those
calls currently  being  handled  by  ACTS  are  lost  or  interrupted;
subsequent coin calls are routed to operators until ACTS is  restored.

  Although only the  active side  of SSAS handles  calls, the  standby
side must keep an  up-to-date copy of data  associated with each  Coin
Detection and Announcement  circuit. Should a  problem develop on  the
active side, the standby side will need this information to take  over
call processing.   The  active  side,  therefore,  continuously  sends
updated call-related information to the standby side.

  TSPS's basic fault-recovery  mechanism is  a switch  to the  standby
side when a fault is detected. There are three ways to do this: with a
smooth switch, an immediate switch, and a rough switch.

  A smooth switch is used when the  active side has a fault that  does
not seriously  affect  call  processing. For  example,  a  single  bit
failure in the announcement store can be tolerated until the switch to
standby is convenient,  since its  impact on  announcement quality  is
insignificant.  Before switching, TSPS first brings the two sides into
approximate synchronization, with the standby side running just behind
the active side.  The switch is then imperceptible to customers.

  An immediate  switch is  made whenever  the active  side develops  a
serious fault, such as control-unit  failure, while the other side  is
on standby.   Since  the  standby memory  is  up-to-date,  only  minor
disruptions in call handling can result.  For example, an announcement
might be interrupted and, after approximately half a second,  repeated
in full.

  A rough  switch is  necessary whenever  the active  side develops  a
fault  while  the  other  side,   normally  on  standby,  is   running
diagnostics.  When TSPS detects a serious fault with the active  side,
it immediately takes that side out of service, halts the  diagnostics,
and forces the standby side to become active.  Since the memory of the
newly active  side is  not up-to-date,  any calls  being handled  when
switching occurred are lost or interrupted. The chance that this might
happen, though is very small.


  Automated Coin  Toll  Service is  helping  to reduce  the  Operating
Company cost of  handling routine  toll calls. It  also monitors  coin
deposits with  greater  accuracy  than  before,  and  helps  Operating
Companies detect trouble at coin stations.

  Automated Coin Toll Service was first installed in Phoenix  Arizona,
in 1977.  Since then,  a rapidly growing number  of the Bell  System's
146 TSPS sites have introduced ACTS.  By the mid-1980s, Automated Coin
Toll Service is expected to be  available for more than 95 percent  of
all Bell System coin statios. At that time, freed from handling  more
than two million  routine coin  toll calls  a day,  operators will  be
better able to help  those customers with  more demanding and  complex
problems--problems that truly require human skills..

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