Announcement system message playback arrangement

In an announcement system comprising a store having a plurality of memory sectors for storing prerecorded messages, a reading head and means responsive to requests for the playback of messages for moving the reading head to selected sectors to read the contents thereof, a method for playing back messages comprising the steps of:

• ordering a first set of sectors associated with a first plurality of messages in a first sequence to minimize the head travel necessary to read the first set of sectors when the heads are moved in a forward direction,
• reading the first set of sectors by moving the head according to the first sequence while accumulating in real time requests for the playback of a second plurality of messages,
• ascertaining that the time utilized for reading the first set of sectors is less than a predetermined amount,
• ordering a second set of sectors associated with the second messages in a second sequence to minimize the head travel necessary to read the second set of sectors when the heads are moved in a reverse direction, and
• reading the second set of sectors according to the second sequence.

For use in an announcement system having a disc memory wherein prerecorded messages are stored in annular tracks of said disc and, wherein responsive to the receipt of playback requests, a reading head is moved to selected ones of the tracks to read the messages stored therein, a method for servicing said requests within a prescribed interval of time comprising the steps of:

• identifying a first set of track locations associated with a plurality of first received requests for playback,
• sorting the first set of track locations in ascending order,
• causing the reading head to seek to each of the first set of track locations in ascending order while identifying a second set of track locations for requests received subsequent to said first requests,
• ascertaining the time interval remaining in said prescribed interval,
• sorting the second set of track locations in descending order when a predetermined time interval remains and in ascending order when less than said predetermined interval remains in the prescribed interval, and
• causing the reading head to seek to each of the second set of track locations according to the result of the last-mentioned sort.

For use in an announcement system for composing announcements in real time from a plurality of prerecorded phrases, said system comprising a disc storage unit for storing said phrases on addressable sectors of said disc and a reading head movable to each said sector for playing back the contents stored therein in response to requests from said announcement system, a method for controlling the playing back of said phrases comprising the steps of:

• translating a plurality of first requests into a first set of sector addresses associated with the requested phrases,
• listing the first set of addresses in a first order wherein consecutive addresses represent disc sectors in closest proximity to each other,
• moving the reading head from an initial position in a first direction according to the first order of addresses to a final position to read the contents of each sector identified by the first set of addresses,
• translating a plurality of second requests into a second set of sector addresses before the reading head is returned to the initial position,
• listing the second set of addresses as a temporary table in said first order,
• reversing the order of the temporary table, and moving the reading head according to the reverse order from the final position to the initial position to read the contents of each sector identified by the second set of addresses.

For use in an announcement system for composing announcements in real time from a plurality of prerecorded phrases, said system comprising a disc storage unit for storing said phrases on addressable sectors of said disc and a reading head movable back and forth across said disc to each said sector for playing back the contents stored therein in response to requests from said announcement system, a method for minimizing reading head movement in response to a plurality of requests for the playback of selected phrases comprising the steps of:

• accumulating in real time requests for the phases associated with an announcement and storing the requests in a queue,
• periodically emptying the queue and translating each request therein into the address of a disc sector containing the corresponding phrase,
• listing the sector addresses so that consecutive addresses represent disc sectors in closest proximity to each other, and
• moving the reading head to each consecutive address on the list by reading the list from one end when the reading head is closest the periphery of the disc and reading the list from the opposite end when the reading head is closest to the center of the disc.