User Manual
3,902,007
1
AUDIO
AND
VIDEO
PLURAL
SOURCE
TIME
DIVISION
MULTIPLEX
FOR
AN
EDUCATIONAL
TV
SYSTEM
BACKGROUND
OF
THE
INVENTION
This
invention
relates
to
eliminating
blanked
guard
band
intervals
from
the
horizontal
scan
lines
of every
branched
video
picture
transmitted
on
a
single
TV
channel
using
line-sharing
techniques.
By
eliminating
the
blanked
guard-band
interval
from
the
transmitted
scan
lines
of
certain
of
the
branched
TV
pictures,
these
pictures
can
be
displayed
occupying
the
full
TV
screen
without
having
a
dark
vertical
band
due
to
the
blank
mg.
The
use
of
television
programming
has
proven
to
be
a
highly
signi?cant
educational
technique.
One
of
the
highly
objectionable
drawbacks
to
the
use
of
television
in
this
regard
has
been
the
need
to
occupy
a
number
of
TV
channels
for
the
simultaneous
transmission
of a
plu
rality
of
different
programs
for
selection
by
a
student.
This
is
undesirable
because
not
only
are
there
a
limited
number
of
TV
channels
available,
but
also
because
the
endless
switching
from
channel-to-channel
will
pro
duce
excessive
wear
or
premature
failure
of
conven
tional
tuner
assemblies.
15
20
-25
Branched
TV
systems
have
been
provided
in
the
past
-
using
different
branching
techniques
whereby
a
plural
ity
of
video
pictures
can
be
transmitted
over a
single
‘
TV
channel.
One
such
branching
system
is
disclosed
in
my
prior
U.S.
Pat.
No.
3,725,571
which
issued
on
Apr.
3,
1973
to
the
Assignee of
the
present
application.
This
prior
system
provides
a
multiplex
video
transmission
system
for
receiving
a
plurality
of n
separate
pictures
wherein
every
nth
line
of
each
of
the
pictures
is
se
lected
for
transmission
beginning
at
a
different
line
and
wherein
reception
of
the
selected
one
of
the
pictures
is
accomplished
by
selecting
from
the
plurality
of
lines
transmitted
every
nth
line
commencing
at
the
prese
lected
line.
The
selected
line
is
delayed
by
a
medium
having
a
bandwidth
less
than
the
bandwidth
of
the
video
pictures
and
recombining
the
undelayed
selected
line
so
that
the
selected
one
of
the
pictures
may
be
dis
played
with
high
quality
resolution.
In
this
form
of
an
educational
TV
system, the
learn
ing
process
can
be
greatly
improved
and
more
versatile
by
providing,
for
example,
one
or
more
audio
channels
containing
instructional
or
even
coded
information
in
addition
to
the
sound
information
provided
by
the
con
ventional
EM.
sound
carrier
in
a
TV
system.
Different
forms
of
educational
TV
systems
have
been
developed
for
transmitting
a
multiplicity
of
video
signals
along
with
audio
and/or
coding
signals
on
a
single
television
carrier
frequency.
One
example
of
such
a
system
is
disclosed
in
my
co
pending
application
Ser.
No.
364,163,
?led
May
25,
1973
and
assigned
to
the
Assignee of
the
present
appli
cation.
This
system
features
a
transmitter
and
receiver
for
a
plurality
of
audio
and
coding
signals
along
with
multiple
pictures.
Bursts
of audio
signals
are
modulated
in
pairs
onto
the
3.6
megahertz
quadrature
phase
sub
carriers
in
the
same
way
as
conventional
I
and
Q
video
signals
are
modulated
onto
the
subscriber.
The
bursts
of
the
audio
signal
are
produced
during
a
blanked
guard-band
interval
de?ned
in
the
video
signal
during
each
horizontal
scan
line
time
period,
the
blanked
guard-band
interval
following the color
reference
burst
30
35
45
55
65
2
in
each
horizontal
scan
line
or,
alternatively,
the
blanked
guard-band
interval
could
be
located
midway
in
the
time
period during
which
luminance
and
chro
mance
video
signals
are
transmitted.
In
this
system
the
blanked
guard-band
interval
ultimately
appeared
on
the face
of
the
receiving
tube
as
a
vertical
bar
or
black
band
located
along
the
left-hand
side
of
the
receiving
tube
in
the
?rst
instance
and
located
midway
between
the
vertical
edges
of
the
picture
tube
in
the
second
in
stance.
In
a
system
of
this
sort,
a
centrally-located
guard-band
interval
was
particularly
useful
since
a
dif
ferent
scene
was
provided
for
display
simultaneously
in
the
four
quadrants of
the
television
receiving
tube.
However,
in
the
TV
system
disclosed
in
the
aforesaid
U.S.
Pat.
No.
3,725,571,
the
presence of a
dark
band
along
one
side
of
the
TV
picture
of
each
of
the
branched
pictures
may
be
annoying
to
the
person
view
ing
the
picture
and
undesirable
since
it
will
occupy
ap
proximately
10%
of
the
total
available
picture
area.
SUMMARY
OF
THE
INVENTION
The
present
invention
provides
an
improved
educa
tional
TV
system
wherein blanked
intervals
are
elimi
nated
during
transmitting
of
at
least
one
branched
video
picture
but
retained
in
other
branched
pictures
whereby
the
video
subcarrier
signals
are
used
part
of
the
time
to
transmit
audio
signal
bursts.
In
accordance
with
the
present
invention,
there
is
provided
in
a
TV
branching
system
an
apparatus
for
and
method
of
transmitting
a
wide-band
audio
signal
during
blanked
guard-band
intervals
during
at
least
one
less
than
each
transmitted
video
picture.
In
a
television
transmitter,
a
method
of
transmitting
Within
a
single
channel
one
or
more
audio
signals
along
with
two
or
more
separate
video
pictures
on
a
video
subcarrier
whereby
the
pictures
are
transmitted
by
se
lecting
a
horizontal
scan
line
from
a
?rst
picture
and
then
selecting
the
next
scan
line
for
transmission
from
a
second
picture
which
is
succeeded
by
selecting
a sub
sequent
occurring
scan
line
from
the
?rst
picture,
the
method
including
the
steps
of
providing
at least
two
audio
signal
transmission
lines,
continuously
sampling
the
audio
signal
in
each
of
the
lines
to
form
audio
bursts
thereof
at
a
rate
less
than
the
horizontal
scan
rate
of
the
video
pictures,
combining
an
audio
burst
from
each
of
the
two
audio
signal
lines
to
form
a
time-separated
train
of
audio
bursts,
and
modulating
the
train
of
audio
bursts
onto
the
video
subcarrier
during
a
blanked
guard-band
interval
in
the
horizontal
scan
lines
se
lected
for
transmitting
at least
one
and
less
than
all
of
the
separate
video
pictures.
v
The
present
invention
further
provides
an
apparatus
for
and
method
of
recovering
audio
signal
bursts
such
as
those
transmitted
by
the
foregoing
method
and
appa
ratus.
The
method
of
recovering
such
audio
signal
bursts
includes
the
steps
of
receiving
within
a
single
television
channel
frequency
the
video
subcarrier
cor
responding
to
the
two
or
more
separate
video
pictures;
selecting
a
signal
corresponding
to
horizontal
scan
lines
from
the
video
subcarrier
containing
the
audio
bursts
during
the
blanked
guard-band
interval;
branching
the
signal
path of
the
signal
corresponding
to
selected
hori
zontal
scan
lines;
time
delaying
the
signal
correspond
ing
to
horizontal
scan
line
signals
in
one
of
the
signal
paths;
and
gating
from
the
signal
corresponding
to
both
of
the
undelayed
and
delayed
horizontal
scan
lines,
the
plurality
of
audio
signal
bursts.