User Manual

3,902,007
provides an undelayed video subcarrier signal to the
add circuit 80 whereby a‘ selected horizontal scan line
by the gate '75 is combined with the same video subcar
rier signal of the scan line after it has been delayed 63.5
microseconds. The output from the add circuit is then
delivered by a line 82 having a first branch portion con
nected to a chroma ampli?er 83 and a second branch
portion connected to a gate 84. The chroma ampli?er
83 delivers its signal to a conventional demodulating
circuit in a TV receiver, not shown. The gate 84 is ren
dered conductive in response to signal pulses ll-ll " and
H2" which are 63.5 microseconds apart plus an addi
tional 2.0 microsecond or 3.0 microsecond, depending
upon the time separation between pulses A1 and A2 at
the transmitter. The pulses H1" and H2” are transmit
ted by line 85 from an audio gate pulse generator and
logic 86 which is controlled in response to the horizon
tal sync pulses delivered from the sync separator 74
and the signal from the line-sharing gate pulse genera
tor and logic 77. The rendering of the gate 84- conduc
tive during each horizontal scan line time period pro
vides a sequence of audio bursts samples having the
time displaced relationship by waveform g in FIG. 5
which are delivered by a line 87 to a detector 88 that
provides an audio signal to a low-pass ?lter 89, thereby
producing the audio waveform h shown in FIG. 5 which
is delivered to an ampli?er 90. This ampli?er drives a
loud-speaker 91.
ln'addition to providing a full picture for one of the
branch video signals there is additionally provided
other advantages which also accrue from the use of the
modi?ed system which are not immediately apparent.
The ?rst of these advantages is that there is less depar
ture during the vertical blanking period from the nor
mal FCC waveform. A further advantage stems from
the use of video recording and playback equipment
wherein one and two head helical tape recorders are
used. When the recording head is switched from one
track to the next, an interruption of the audio and video
signals occurs. Since this interruption occurs once per
?eld, it can cause a 60 hertz buzz in the sound. If the
interruption is arranged so as to occur between two
audio bursts, the crossover tolerance is 11/2 horizontal
scan line.
Although the invention has been shown in connec
tion with certain speci?c embodiments, it will be
readily apparent to those skilled in the art that various
changes in form and arrangement of parts may be made
to suit requirements without departing from the spirit
and scope of the invention.
What is claimed is:
1. ln a television branching system, a method of
transmitting within a single television channel one or
more audio signals along with two or more separate and
branched video pictures on the same video subcarrier,
said method including the steps of:
forming ?elds of a video signal consisting of selected
scan lines from two or more separate video pictures
by selecting for transmission a horizontal scan line
corresponding to a ?rst video picture and then se
lecting the next horizontal scan line for transmis
sion from a second picture which is then succeeded
by selecting for transmission a subsequent occur
ring horizontal scan line from said ?rst picture;
providing at least two audio signal lines;
continuously sampling the audio signal in each of said
audio signal lines to form audio bursts thereof at a
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rate less than the occurring rate of selected hori
zontal scan lines forming the ?elds of video signal;
combining the audio bursts from the two audio signal
lines to form a time—separated train of audio bursts
in such a manner so that the formed train of audio
bursts occur only during the horizontal scan lines
selected for transmitting at least one and less than
all of the video pictures;
generating a blanked guard~band interval in the hori»
zontal scan lines forming the video signal frames of
at least one and less than all of said two or more
pictures and at a time apart from the horizontal re
trace period including occurring horizontal sync
pulses in such a manner that a displays-.3 image of
at least one but less than all of the pictt....s will in
clude blanked video intelligence corresponding to
the blanked guard-band interval; and
modulating the selected lines of said video pictures
onto a video subcarrier while modulating said train
of audio bursts onto the same video subcarrier dur
ing the generated blanked guard-band interval in
the video signal portion of horizontal scan lines se
lected for transmitting at least one and less than all
of the separate video pictures.
2. The method according to claim 1 including the ad
ditional step of delaying the audio signal in one of said
audio signal transmission lines for a period of time cor
responding to at least one video scan line time period.
3. The method according to claim 2 wherein said sig
nal transmission lines each receive the same audio sig‘
nal.
4. The method according to claim ll wherein said Sig
nal transmission lines each receive a separate and inde
pendent audio signal.
5. The method according to claim ll wherein the con
tinuous sampling of the audio signal in each of said sig
nal transmission lines produces audio bursts occurring
at different times.
6. The method according to claim 5 wherein the con
tinuous sampling of the audio signal in each of said sig
nal transmission lines produces an audio burst for every
two video scan lines transmitted.
7. In a television branching system, the method of re
covering from a video subcarrier within a single chan
nel frequency in a receiver at least one audio signal
transmitted along with at least one and less than all of
two or more separate and branched video pictures, said
audio signals being transmitted in the form of a plural
ity of audio bursts during a blanked guard-band interval
which occurs within the video intelligence portion of
the horizontal scan lines selected to transmit at least
one and less than all of two or more separate and
branched video pictures, said method including the
steps of:
receiving said video subcarrier modulated with said
two or more separate and branched video pictures
of which at least one and less than all contain a
blanked band in the video when displayed on the
face of a television display tube, said blanked band
corresponding to said blanked guard-band interval;
selecting a video signal from said video subcarrier
corresponding to horizontal scan lines forming only
the separate and branched video pictures which
when displayed include said blanked band and
thereby selecting only the horizontal scan lines in—
cluding said plurality of audio bursts during the