illuminates red to show the write protect function
is for the console indicators and relays. The next
is operating. The second LED, under the label
two fuses are spares.
RDY, illuminates yellow to show main power has
been applied to the cassette drive and it is ready
to read/write. The third LED, under the label
BSY, illuminates yellow to show data is being
transferred. The second row of three LEDs are
for memory drive No. 1 (DR1) and are identical
to the first row.
Bubble Memory Section
The bubble memory system stores digital data,
like a floppy or hard disk of a personal computer.
In the DDG-51 MCS, the data is the computer
program that operates the console. When the
console is powered up, the computer automatically
loads the program from the bubble memory
cartridges. (This "bootstrap" function of the
computer is equivalent to a personal computer's
AUTOEXEC program.) A lot of computer data
is stored magnetically--such as on floppy and
hard disks. In the bubble memory, the data bits
AN/USH-26 Section
are stored as magnetic bubbles. Bubbles improve
reliability because they are moved, stored, read,
Figure 7-3 shows the AN/USH-26 with the
or written electrically; there are no mechanical,
door removed for clarity. It is a data cartridge
moving parts. The bubbles do not have to move
magnetic tape storage and data transfer device.
past a read/write head, as opposed to the floppy
It is used with the AN/UYK-44 computer in the
or hard disk. The main advantage of the bubble
EOOW/LU for loading bubble memory cassettes
memory is its resistance to electromagnetic
and for logging data associated with the DDG-51
machinery. It operates under the control of
The bubble memory cassettes store a unique
the AN/UYK-44 and, during normal on-line
program for each of the AN/UYK-44 computers.
operation, requires minimal operator interface.
The cassettes are loaded from the AN/USH-26
The tape unit contains two tape drive assemblies,
magnetic tape unit in the EOOW/LU using the
a card cage assembly, power supplies, a
AN/UYK-44 input/output controller, the bubble
maintenance panel, and front panel controls and
memory drive, and the work station plasma
indicators.
display and keyboard in the EOOW/LU.
The two tape drive assemblies, labeled DRIVE
The bubble memory is contained in an
0 and 1, respectively, are identical and have iden-
enclosure of welded aluminum alloy. The major
tical controls and indicators. Each tape drive has
items of the unit are two 256K-byte (256
an alarm indicator, a two-position toggle switch,
thousand) memory cassettes, interface and
a rotary switch, and four LEDs. We will describe
control circuit card assemblies, and a dc power
only the controls and indicators for drive 0.
supply. These units (not shown) are enclosed
Starting at the top left of the tape drive
behind the access doors in the front of the panel.
assembly is the alarm indicator, labeled HOT. It
The front panel has a power on/off switch and
is an incandescent bulb with a red cover lens.
seven LED indicators. The power on/off switch
When the bulb is illuminated, it shows the tape
is a two-position toggle switch (normally on) that
drive assembly temperature > 165F. It will also
controls power to the bubble memory drive. The
illuminate when the ALARM/ENABLE/TEST
first LED, labeled POWER, illuminates green to
switch (described later), located at the lower right
show power is turned on to the bubble memory
of the control panel, is set to the TEST position.
drive. The top row of three LEDs, labeled DRO
Below the alarm indicator is the two-position
(at the right), are for memory drive No. 0. The
toggle switch, labeled ON LINE/OFF LINE. It
first LED in the top row, under the label WP,
7-4
