BASF 6106 - Page 30

2.2.8. READ/WRITE
CIRCUITS
2. 2. 8.1.
READ/WRITE
HEAD
The
read/write
head used in
the BASF 6106
is
a
tunnel erase
type
ceramic
head.
It records
and
reproduces
data at a flux
density of 3S36
to
5536 flux
changes per inch
(fci)
The nominal
frequency
measured
on
the
read/write
head for
an
"
all
O's
"
pattern is 62,5
kHz and
125 kHz
for
an
"
all
1*s
"
pattern
*hen t-M
recording
technique
is
used.
The
nominal
time
between
flux
rever-
sals is
8
/usee (all
0)
or
4 yusec
(
all 1
)
.
The radial
density
is
48 tracks per inch (tpi)
.
This gives 0,0208
inch nominal track to track
spacing. The tunnel erase gaps
trims the track
width to 0,014
inch
after
write
and to
0,012
inch
after erase (see Fig.
2
-
27 ).
The
read/write nead contains three
coils:
two
read/write coils and
the erase coil
(see
Fig.
2-28
).
The erase coil is
energized
during
every
write
operation
and
limits
the
track
width
and
provides
low
noise
guard
bands
on
each
side
of the
recorded
track.
The
two
read/write
coils
are wound
on a
single
core
and
are
center
tapped.
The
electrical
connec-
tions
of
the
read/write
head
are
shown
on
fig.
2
-
28 . During
a
write
operation
each
bit
written
will
be
directed
alternately
to
one
of
the
two
read/write
coils
by
a
flipflop.
This
causes
a
flux
change
for
every
bit
to
be
written.
The
old
data
on
the
track
will
be
overwritten
by
the
new
data
stream.
On a
read
operation
an
output
voltage
is
induced
in the
read/write
head
by
every
flux
change
that
passes
the
gap
of
the
read/write
head.
This
voltage
is
used
by
the
read
circuits
to
recover
the
written
data.
TRACK
N*
I
,t~:-~
20.8
mil
8.8
mil
a....
. .
*
—
14 mil/SSSxTRACK
N
J
12
mil
I
WRITTEN
DATA
™™
EL
ERASED
DATA
INPUT
FROM
WRITE
DRIVER
OR
OUTPUT
TO
READ
AMPLIFIERS
CENTER
TAP
X
FIGURE
2
-
27
.
TRACK
GEOMETRY
FIGURE
2
-
28 .
ELECTRICAL
CONNECTION
OF THE
READ/
WRITE
HEAD
2-20