US3649749A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus permitting reliable selection of transmitted television message information
Assignee: RCA Corp
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Filing: 1970-10-21
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Granted: 1972-03-14
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Expires: 1990-10-21
Abstract
Abstract A digital countdown circuit is synchronized by a ''''flag'''' signal transmitted every other television field to permit reliable selection of a predetermined television frame line in a system transmitting auxiliary television message information. The ''''flag'''' signal can be unreliable in the sense that the countdown circuit can miss the ''''flag'''' in a large percentage of cases, but is reliable in the sense that the probability of mistaking other signals as the desired ''''flag'''' is small, even in the presence of noise which impairs the quality of the received television picture.
Inventors
- 👤 J James Gibson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:29
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/08; H04N7/087
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
376 words
In a television system of the type wherein message information is multiplexed between predetermined line scanning rate pulses of a broadcast signal to provide an auxiliary transmission service which is in addition to that provided the picture tube of the receiver employed in such system, wherein said broadcast signal comprises at least two alternating interlaced fields containing a field scanning rate pulse in addition to said line scanning rate pulses, and wherein the timing of the leading edge of said field scanning rate pulse differs with respect to the timing of said line scanning rate pulses on alternate ones of said two interlaced fields, apparatus for permitting the reliable selection of desired message information from said broadcast signal for the subsequent recovery and reproduction thereof, comprising; means supplying timing pulses at a frequency equal to that of said line scanning rate pulses and substantially in time synchronism therewith; counter means counting that number of pulses supplied by said last-mentioned means which corresponds in number to the line scanning rate pulses present in each of said alternate interlaced fields before resetting to zero upon reaching said count; digital logic means coupled to said counter means for providing an output pulse in response to said counter means counting to that number which corresponds to the position between said predetermined line scanning rate pulses in which said desired message information is multiplexed; means supplying said multiplexed broadcast signal including saiD desired message information and said scanning rate pulses; means responsive to the output pulse provided by said digital logic means and to said supplied broadcast signal for mixing said signals together for recovering the desired message thereof to the exclusion of said multiplexed scanning rate pulses; and means additionally responsive to said supplied timing pulses for additionally transmitting a control signal only on one of said two interlaced fields of said broadcast signal to synchronize said counter means and thus, stabilize the timing of the leading edge of said provided output pulse and the time of occurrence of said recovered signal; said control signal being transmitted during said one interlaced field at a substantially low amplitude level with respect to the blanking level of said picture tube so as to limit detrimental interference with the retrace of said tube.
Claim 2
Dependent Claim
376 words
In a television system of the type wherein message information is multiplexed between predetermined line scanning rate pulses of a broadcast signal to provide an auxiliary transmission service which is in addition to that provided the picture tube of the receiver employed in such system, wherein said broadcast signal comprises at least two alternating interlaced fields containing a field scanning rate pulse in addition to said line scanning rate pulses, and wherein the timing of the leading edge of said field scanning rate pulse differs with respect to the timing of said line scanning rate pulses on alternate ones of said two interlaced fields, apparatus for permitting the reliable selection of desired message information from said broadcast signal for the subsequent recovery and reproduction thereof, comprising; means supplying timing pulses at a frequency equal to that of said line scanning rate pulses and substantially in time synchronism therewith; counter means counting that number of pulses supplied by said last-mentioned means which corresponds in number to the line scanning rate pulses present in each of said alternate interlaced fields before resetting to zero upon reaching said count; digital logic means coupled to said counter means for providing an output pulse in response to said counter means counting to that number which corresponds to the position between said predetermined line scanning rate pulses in which said desired message information is multiplexed; means supplying said multiplexed broadcast signal including saiD desired message information and said scanning rate pulses; means responsive to the output pulse provided by said digital logic means and to said supplied broadcast signal for mixing said signals together for recovering the desired message thereof to the exclusion of said multiplexed scanning rate pulses; and means additionally responsive to said supplied timing pulses for additionally transmitting a control signal only on one of said two interlaced fields of said broadcast signal to synchronize said counter means and thus, stabilize the timing of the leading edge of said provided output pulse and the time of occurrence of said recovered signal; said control signal being transmitted during said one interlaced field at a substantially low amplitude level with respect to the blanking level of said picture tube so as to limit detrimental interference with the retrace of said tube.
Claim 3
Dependent Claim
72 words
The apparatus of claim 1 wherein said broadcast signal comprises an ''''even'''' interlaced television field signal and an ''''odd'''' interlaced television field signal, each of which contain equalizing pulses in addition to said scanning rate pulses, and wherein said control signal is transmitted during said ''''even'''' interlaced field signal between those line scanning rate pulses which come after the last equalizing pulse following the field scanning rate pulse of said interlaced signal.
Claim 4
Dependent Claim
58 words
The apparatus of claim 1 wherein there is additionally included second counter means coupled to said digital logic means to provide an output pulse, the state of which is indicative of whether said means supplying said multiplexed broadcast signal is then supplying the ''''odd'''' interlaced field signal or the ''''even'''' interlaced field signal of said television broadcast signal.
Claim 5
Dependent Claim
78 words
The apparatus of claim 1 wherein the timing of the leading edge of said field scanning rate pulse is subject to tolerance variations and wherein said transmitted control signal is coupled to said counter means to insure its setting at a predetermined count to stabilize the leading edge of the output pulse developed by said digital logic means as being with respect to said supply timing pulses rather than with respect to said varying field scanning rate pulses.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-14 | 1975-09-13 | 1976-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-14 | 1979-09-13 | 1980-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-14 | 1983-09-13 | 1984-03-14 | $7700.00 | Window Closed / Lapsed |