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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.
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HANDLING COIN TOLL CALLS --AUTOMATICALLY
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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
assistance.
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
well.
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
overtime".
Talks for three minutes. "Three minutes has ended.
Please signal when
through".
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.
CONNECTIONS
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
taken.
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
customer.
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
operator.
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
sentences.
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.
RELIABILITY
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.
BENEFITS
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..