342 lines
19 KiB
Plaintext
342 lines
19 KiB
Plaintext
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I receved the following documment from a friend who was then a TSPS
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operator, one year ago -- just before LA cut over to the ACTS/SSAS
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system. In light of some recent discussion over automated coin
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telephone service, and automatic calling card service as well, I am
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submitting it to the list.
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><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><
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HANDLING COIN TOLL CALLS --AUTOMATICALLY
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- - - - - - - -
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Automated Coin Toll Service handles
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the routine aspects of coin-paid toll calls, freeing operators
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to deal with more complex customer interactions.
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By James O. Hardy, Dattatraya G. Raj-karne, and Kenneth A. Raschke
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"Sixty cents, please. Please deposit 60 cents for the first three
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minutes". The message is familiar, the voice is invariably pleasant
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and cheerful. What you may not know, however, is that the "operator"
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at the other end is not human-- it's a machine. By taking over the
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routine tasks associated with handling coin toll calls, this machine
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frees operators to concentrate on more complex calls, such as collect
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or third party billing, and to help any customers who may require
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assistance.
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Automated Coin Toll Service (ACTS) is the feature that makes it all
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possible. ACTS automatically computes charges on coin toll calls,
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announces charges to the customer, counts coin deposits, and sets up
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coin calls--all without the need for an operator.
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ACTS was developed for use with the Traffic Service Position
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System--an "electronic switchboard" that, since 1969, has been helping
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operators handle toll and other calls requiring assistance. Today, The
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Traffic Service Position System--known as TSPS--serves about 90
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percent of the Bell System's coin-paid toll calls on an average
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business day. Automated Coin Toll Service works with TSPS to
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eliminate or reduce operator tasks on many of the coin-paid calls.
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ACTS can also make announcements for some non-coin operator-assisted
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calls. For instance, when a customer requests time and charge
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quotations, the operator indicates this to the TSPS processor; then at
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the end of the call, TSPS instructs ACTS to make the appropriate
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announcement--for example, "The charges are three dollars and 30 cents
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plus tax for seven minutes". Also, if a customer asks to be notified
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after a specified amount of time, the operator inputs the specified
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time to the TSPS processor. Then, at the correct time, TSPS instructs
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ACTS to make an announcement, such as "Six minutes has ended".
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When a customer makes a station-to-station toll call from a coin
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telephone, the local central office routes the call to its associated
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TSPS. In areas served by Automated Coin Toll Service, the TSPS central
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processor connects the call to the Station Signaling and Announcement
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Subsystem (SSAS) hardware that provides Automated Coin Toll Service.
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SSAS is an "intelligent peripheral" subsystem, receiving instructions
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from and sending data to the TSPS central processor.
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SSAS TAKES OVER
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TSPS provides information to SSAS about call charges and the length
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of the initial period for the call. Using this information, SSAS
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constructs and sends a series of announcements to the customer. The
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first gives The initial charge for the call. The customer might hear,
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for example, "One dollar and 20 cents please [two second pause] please
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deposit one dollar and 20 cents for the first three minutes".
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If the customer deposits a coin during the initial request, the
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announcement is truncated immediately. This announcement allows a
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customer to deposit the required amount without listening to the
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entire deposit request. As the customer deposits money, SSAS detects
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each coin signal, and totals the amount deposited. When the correct
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amount has been deposited, SSAS returns control to TSPS, which
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completes the call connection. If the customer deposits too much,
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SSAS tells the customer that the additional money is credited toward
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overtime. Should the customer fail to deposit enough money within a
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reasonable time, SSAS generates a prompting announcement. If no money
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is deposited after the prompting announcement, TSPS adds an operator
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to the connection. A customer can also reach an operator by flashing
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the switchhook.
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If the customer is still using the phone at the end of the initial
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period-- usually three minutes--TSPS again connects SSAS to the call,
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and orders it to tell the customer that the initial period has ended.
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If the customer talks beyond the initial period and then hangs up,
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TSPS rings back. When the customer picks up, TSPS instructs SSAS to
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request overtime charges, and to monitor coin deposits. If the
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customer talks for a long time after the initial period, TSPS
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periodically instructs SSAS to request and collect interim deposits as
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well.
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In short, with Automated Coin Toll Service, SSAS performs two major
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functions previously requiring operators: It provides announcements to
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the customer, and it monitors coin deposits. To provide these
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functions, SSAS relies on three principal components: a number of Coin
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Detection and Announcement circuits to connect customers to SSAS; a
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control unit to coordinate the sending of voice signals over those
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circuits and to interface with the TSPS processor; and a solid-state
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announcement store to hold digitized voice signals.
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Sample dialog
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Customer ACTS/TSPS
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Picks up handset Dial-tone (from local office)
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Dials number "One dollar and 20 cents
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please. [pause] Please
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deposit one dollar and
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20 cents for the first
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three minutes".
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Deposits $1.10. Drops dime "Please deposit 10 cents
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on floor and searches for more".
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six seconds.
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Gives up search and "Thank you. You have 15
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deposits quarter. cents credit toward
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overtime".
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Talks for three minutes. "Three minutes has ended.
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Please signal when
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through".
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Talks for two more Ringback of calling phone.
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minutes and hangs up.
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Picks up handset. "Twenty-five cents please.
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[pause] You have 15 cents
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credit. Please deposit
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25 cents more for the
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past two minutes".
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Deposits 25 cents. "Thank you".
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Hangs up.
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CONNECTIONS
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Coin Detection and Announcement (CDA) circuits provide the link
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between the customer at the coin station, and the control unit of the
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Station Signalling and Announcement Subsystem. Each CDA circuit can
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convert digitized speech from the announcement store into analog voice
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announcements. In addition, each CDA circuit contains a data receiver
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to detect coin-deposit signals generated by the coin station;
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different signals distinguish nickel, dime and quarter deposits.
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An individual CDA circuit handles just one call at a time. The
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number of CDA circuits needed to handle coin toll calls for a TSPS
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office can therefore vary widely from one location to another.
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Presently, each SSAS can handle a maximum of 239 announcement
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circuits. Normally, though, only 30 to 100 CDA circuits are needed to
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handle coin toll traffic, even in large metropolitan offices. The
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additional circuit capacity is available for use in the future to
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provide new automated TSPS services.
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MICROPROCESSOR CONTROL
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The SSAS control unit contains its own microprocessor, or
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programmable controller--the "intelligent" part of SSAS. The
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programmable controller handles the internal control-unit operations
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and, together with other circuitry, transfers voice data bits from the
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announcement store to the CDA circuits, and communicates with the TSPS
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processor. Because of its central role in the control unit, the
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programmable controller has several self-checking capabilities. Some
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functions within the controller are duplicated, so that errors can be
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detected by comparing the controller outputs. The control unit also
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checks for errors in the program instructions by examining special
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binary digits called "parity bits" at the end of each "word" of
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instruction. Wherever a programmable controller error is detected,
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TSPS is notified so that the appropriate fault recovery actions can be
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taken.
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When a customer starts to make a coin-station call, TSPS instructs
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the control unit to make an initial announcement to the customer over
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a specified CDA circuit. TSPS provides the control unit with
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information about the required deposit and the length of the initial
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call period. Using this information, the control unit determines the
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appropriate announcement, and begins to retrieve, sequentially, the
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required data from the announcement store. The announcement store
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data are converted into a digital serial bit stream and transmitted to
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the specified CDA circuit. Here, the serial bit stream is converted
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into an analog signal, and the resulting announcement routed to the
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customer.
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As the customer deposits coins in response to announcements, the
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control unit interrogates the CDA circuit for coin-deposit
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information. The control unit totals the coins deposited and, when
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the amount paid matches the amount required, acknowledges the correct
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deposit with a "Thank you". When appropriate, the control unit
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initiates an announcement requesting additional money or acknowledges
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credit for overdeposits. Finally, the control unit notifies TSPS when
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the deposit is satisfactory--or, if the customer has not deposited the
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coins quickly enough, that TSPS should connect the customer to an
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operator.
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To ensure that ACTS will serve customers most effectively, and to
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encourage customers to deposit coins promptly and accurately, a good
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deal of attention has been directed toward the customer-machine
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interaction. Announcements must be intelligible, carefully worded,
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and appropriately timed. So a human factors study was conducted in
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1975 with the cooperation of Illinois Bell in Chicago, to aid in
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determining an efficient set of phrases, sentences, and timing
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parameters for the machine-generated ACTS announcements.
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SPEECH SEGMENTS
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ACTS announcements are constructed from a set of 512-millisecond
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"speech segments". Each segment is equivalent to about one word of the
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ACTS vocabulary. Under the direction of the control unit, individual
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words or word segments are retrieved from the announcement store and
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strung together to form announcement phrases and sentences. Most
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words, such as "cents" or "minutes" require a single speech segment;
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some words, such as "fifteen" and common phrases such as "Please
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deposit" require two speech segments. A few phrases such as "Please
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signal when through" require three speech segments. Each phrase
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involving two or three speech segments could have been formed by
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stringing together the appropriate individual words, each encoded as a
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separate 512-millisecond speech segment. More natural sounding speech
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results, however, if the phrase is treated as a complete unit
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requiring one or one-and-a-half seconds of encoded speech--that is two
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or three contiguous speech segments.
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The vocabulary of about 80 words presently required for ACTS
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announcements was initially recorded by a professional announcer. The
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words were then digitally encoded using a process called Adaptive
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Delta Modulation and organized into eighty 512-millisecond segments.
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Each segment (word) or group of segments (long word or phrase) was
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adjusted to a consistent level and pitch with silent periods inserted
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where needed. This results in natural-sounding speech when the
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segments are joined together in various combinations to form
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sentences.
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To store announcement speech segments, SSAS uses the same type of
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semiconductors memory that is currently used by the TSPS central
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processor. Each 512 millisecond speech segment requires that 16,000
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bits of information be stored, grouped into 400 individual "data
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words". A data word contains 47 binary digits or bits; 40 of these
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are for announcement data, and seven for error checks.
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The announcement store must serve a maximum of 239 CDA circuits
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simultaneously- even releasing the same speech segment to all circuits
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at the same time if necessary. But the store is equal to the task: It
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can release the data at the rate of eight million bits per
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second--equivalent to 40 bits of data every five microseconds. This
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rate ie 256 times the speed at which digitized speech segments are
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decoded by each CDA circuit and converted to analog speech.
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Consequently, designers devised a "time multiplexed" arrangement
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whereby the announcement store retrieves one 40-bit data word every
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five microseconds, and distributes that data word to any one of 256
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circuits. Of these, 239 are for CDA service to customers, and 17 are
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for diagnostic and fault testing.
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It takes 1.28 milliseconds to distribute a data word to each of the
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256 circuits in sequence. Four hundred repetitions of the distribution
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sequence release 400 40 bit data words to each circuit every 512
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milliseconds. This is precisely the rate required to produce
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simultaneous, uninterrupted announcements, each consisting of several
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512-millisecond segments joined together.
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Although the vocabulary required for coin traffic might appear to be
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constant, it can in fact change. This is because call-handling
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practices sometimes change, and because any future developments for
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Automated Coin Toll Service may require vocabulary changes or
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additions. Also a significant number of words will be needed as new
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automated features are added to TSPS. The capabilities of the SSAS
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random access memory permit vocabulary changes to be incorporated
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readily, and permit expansion of the vocabulary to include up to 480
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speech segments.
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RELIABILITY
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Because Automated Coin Toll Service must be highly reliable, parts
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of the SSAS hardware are duplicated. Several sophisticated techniques
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detect faulty operation, evaluate its seriousness, and then bypass or
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remove the faulty part from service at the most appropriate time.
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For backup in case of failure, SSAS has two identical control units
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and announcement stores. One control unit and its dedicated
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announcement store constitute the "active" side and handle all calls;
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the other control unit and announcement store are called the "standby"
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side. The standby side is made active when the other side fails.
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Extensive self-checking and fault-detecting capabilities within each
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side allow many operations to occur independently, minimizing
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interaction and common circuitry between the two sides. Consequently,
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there are very few single hardware faults that can cause both sides of
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SSAS to fail simultaneously. If such a fault does occur, only those
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calls currently being handled by ACTS are lost or interrupted;
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subsequent coin calls are routed to operators until ACTS is restored.
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Although only the active side of SSAS handles calls, the standby
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side must keep an up-to-date copy of data associated with each Coin
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Detection and Announcement circuit. Should a problem develop on the
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active side, the standby side will need this information to take over
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call processing. The active side, therefore, continuously sends
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updated call-related information to the standby side.
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TSPS's basic fault-recovery mechanism is a switch to the standby
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side when a fault is detected. There are three ways to do this: with a
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smooth switch, an immediate switch, and a rough switch.
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A smooth switch is used when the active side has a fault that does
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not seriously affect call processing. For example, a single bit
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failure in the announcement store can be tolerated until the switch to
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standby is convenient, since its impact on announcement quality is
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insignificant. Before switching, TSPS first brings the two sides into
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approximate synchronization, with the standby side running just behind
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the active side. The switch is then imperceptible to customers.
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An immediate switch is made whenever the active side develops a
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serious fault, such as control-unit failure, while the other side is
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on standby. Since the standby memory is up-to-date, only minor
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disruptions in call handling can result. For example, an announcement
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might be interrupted and, after approximately half a second, repeated
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in full.
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A rough switch is necessary whenever the active side develops a
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fault while the other side, normally on standby, is running
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diagnostics. When TSPS detects a serious fault with the active side,
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it immediately takes that side out of service, halts the diagnostics,
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and forces the standby side to become active. Since the memory of the
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newly active side is not up-to-date, any calls being handled when
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switching occurred are lost or interrupted. The chance that this might
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happen, though is very small.
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BENEFITS
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Automated Coin Toll Service is helping to reduce the Operating
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Company cost of handling routine toll calls. It also monitors coin
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deposits with greater accuracy than before, and helps Operating
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Companies detect trouble at coin stations.
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Automated Coin Toll Service was first installed in Phoenix Arizona,
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in 1977. Since then, a rapidly growing number of the Bell System's
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146 TSPS sites have introduced ACTS. By the mid-1980s, Automated Coin
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Toll Service is expected to be available for more than 95 percent of
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all Bell System coin statios. At that time, freed from handling more
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than two million routine coin toll calls a day, operators will be
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better able to help those customers with more demanding and complex
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problems--problems that truly require human skills..
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