CA1322592C - Control of rf pulses in a tv answer back system - Google Patents
Control of rf pulses in a tv answer back systemInfo
- Publication number
- CA1322592C CA1322592C CA000552649A CA552649A CA1322592C CA 1322592 C CA1322592 C CA 1322592C CA 000552649 A CA000552649 A CA 000552649A CA 552649 A CA552649 A CA 552649A CA 1322592 C CA1322592 C CA 1322592C
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- receiver
- oscillator
- transmitting
- television
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
- H04N7/17309—Transmission or handling of upstream communications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/65—Arrangements characterised by transmission systems for broadcast
- H04H20/71—Wireless systems
- H04H20/72—Wireless systems of terrestrial networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H60/00—Arrangements for broadcast applications with a direct linking to broadcast information or broadcast space-time; Broadcast-related systems
- H04H60/29—Arrangements for monitoring broadcast services or broadcast-related services
- H04H60/33—Arrangements for monitoring the users' behaviour or opinions
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H60/00—Arrangements for broadcast applications with a direct linking to broadcast information or broadcast space-time; Broadcast-related systems
- H04H60/76—Arrangements characterised by transmission systems other than for broadcast, e.g. the Internet
- H04H60/81—Arrangements characterised by transmission systems other than for broadcast, e.g. the Internet characterised by the transmission system itself
- H04H60/90—Wireless transmission systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
- H04N2007/17372—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal the upstream transmission being initiated or timed by a signal from upstream of the user terminal
Abstract
CONTROL OF RF PULSES IN A TV ANSWER BACK SYSTEM
ABSTRACT OF THE DISCLOSURE:
In a TV answer back system where many receiver stations communicate with a TV transmitter station by means of rf pulses generated by rf oscillators at the receiver station, the requirement for keeping all oscillators on frequency is achieved without crystal control by automatically controlling the rf oscillator frequency using synchronization signals carried in the video signal received from the TV
studio. By this invention it has been possible to control the frequency of multiple megahertz oscillator as accurately as desired from relatively low frequency synchronizing signals Such as the vertical and horizontal video sync pulses. Thus an oscillations counter is gated for a very accurate time period by the sync pulses, and the oscillation count is compared with a datum count representing the desired oscillation frequency. The requirement to prevent receiver stations from answering with rf pulses in response to querles contained in home video recordings of previously broadcast signals is achieved by encoding broadcast time on all query containing TV transmissions, and by comparing at receiver stations broadcast time Information from received signal with time from a local battery backed clock contained at each receiver station, thus discrimination of video recordings is possible by comparing received video broadcast time with local time.
ABSTRACT OF THE DISCLOSURE:
In a TV answer back system where many receiver stations communicate with a TV transmitter station by means of rf pulses generated by rf oscillators at the receiver station, the requirement for keeping all oscillators on frequency is achieved without crystal control by automatically controlling the rf oscillator frequency using synchronization signals carried in the video signal received from the TV
studio. By this invention it has been possible to control the frequency of multiple megahertz oscillator as accurately as desired from relatively low frequency synchronizing signals Such as the vertical and horizontal video sync pulses. Thus an oscillations counter is gated for a very accurate time period by the sync pulses, and the oscillation count is compared with a datum count representing the desired oscillation frequency. The requirement to prevent receiver stations from answering with rf pulses in response to querles contained in home video recordings of previously broadcast signals is achieved by encoding broadcast time on all query containing TV transmissions, and by comparing at receiver stations broadcast time Information from received signal with time from a local battery backed clock contained at each receiver station, thus discrimination of video recordings is possible by comparing received video broadcast time with local time.
Description
1~23(~2 l l l LI~:
CONTROL OF RF PULSES_IN A rv ANSWER BACK SYSTEM
I ECI-IN I C~L i- I ELI):
This inventlon relates to TV answer back systems whereln rf answer 5pulses are transmltted rrOm recelver locatlons to TV studlos In response t to querles sent from TV studlos on the TV siynal, and more partlcularly It relates to the control of the carrier frequency at wh~ch the rf pulses are generated at the recelver locations, and to tl~e control and preventlon of false answer pulses from belng transmltted from recelver locatlons In 10response to querles recelved from a playback of a vldeo recordlng of a broadcast TV slgnal.
B~\CKGROUND ART:
In the TV answer back system of our U.S. Patent 4,591,906 i~ay 27, 1986 for Wireless Transmission from the Televlslon Set to the Televlslon 15Statlon, rf beep answers are transmltted by wlreless transrnlsslon from receiver statlons at very hlgh frequenciessuchas 53 megahertz or hlgher.
In thls system all receivers are operatlng on tl~e same answer back frequency. It ~s Imperatlve then that all the receivers have very carefully controlled answer back frequency to provlde a very narrow bandwldth 20necessary for the communlcatlo!) channel, and to assure tl~at all answers are recelved and processed at tl~e TV studlo. One means of control Is to provlde temperature compensated or oven crystal controlled osclllators at each recelver statlon. However, for mal-y thousand statlons In tl~e range of a slngle TV transmitter, tl~ls Is an expensive and unrellable undertaklng as 25shocks, aglng, and other factors that affect oscillatlon frequency can not be controlled In a l~ome envlroment.
Also, In a given geographlcal area, several TV slgnals ~rom TV statlons and ca~le channels may request answers slmult3ne()usly, and recelver ~ ~ ~, 2 .~?,..~
stations with capablllty to answer back In two or more fre~uer)cels rrlay i e deslrable. Accordlngly It Is an obJective of thls Inventlon to provlde Inexpenslve and accurate control of osclllators locate(J at recelver stations, in systems wlth slngle or multlple answer back frequencles.
The foregoing obJective ralses a serlous problem, namely that a very hlgll mult~ple megahertz oscillation frequency need be accurately frequency controlled wlthout crystals in a home envlronment where temperatures, voltages and other operatlonal conditlons vary slgnlficantly, ther~by t~nding to vary the oscillator frequency.
It is also deslrable to have a frequency control system compatible with the technology used in the answer back equipment In order to further reduce cost. Thus, the use of pulse countiny microprocessor technology Is preferred. Thls then raises a problem that heretofore has not been resolved.
.. namely it does not seem possible to control the megahertz osclllator frequency accurately withln very few parts per rnilllon wlthout havlng local means to control the enYironment (as In oven crystals), or to : ` compensate for changes In amblent codltlons (temperature compensation), or to adJust for changes due to aglng ( manual screw adJustments).
In a TV answer back system where TV statlons encode query slgnals Into the vl(;ieo slynal"~ecelver slatlor)s sen~i rf answer pulses In resf~onse to querles contalned In the vldeo slgnal, however, recelver statlons wlll also send rf answer pulses In response to a vldeo slgnal comlng from a home vldeo recorder when tl~is slgnal was orlyinaly recorded frorn a TV
broadcast contalnlng encoded querles. Tl~is tl~en ralses a problell) that heretofore l~as not been resolved, naloely it does not seem possible to discrlmlnate from a live TV slgnal containing ~uerles and from a home vldeo recording of a TV slgnal containil-g ~lueries, and thus pl event recelver statlons from sending rf answer pulses th3t may Intel fere with . .
. ~ ' t'3 L;3 ~ S;j r~ l~ .J ~ ,J
answers from live broadcast queries.
DISCLOSURE OF THE INVENTION: . r Accordingly, the invention in one broad aspect pertains to a television system having a plurality of television receiver 5 stations operable to reproduce multiple live and recorded television signals from various sources wherein there is apparatus for distinguishing receiver operation in response to live and recorded signal sources. The apparatus comprises in combination means at a television transmitting station for lO accurately controlling a time signal and transmitting it on a live television signal, means operable to receive the time signal at a television receiving station, and detection means at the receiver station for comparing the received transmitter time signal with a time signal being produced at the receiving station 15 to determine when a live broadcast is being reproduced.
Another aspect of the invention comprehends a television transponder system having a plurality of television receiver stations capable of sending information in response to a viewer's response to a querying television transmitting studio which is 20 transmitting queries to receivers on video signals. The system comprises in combination, transmitters at all the receiver stations having oscillators for transmitting respectively on a single very high transmission frequency of a predetermined number of megahertz unmodulated pulses at precise times for identifying 25 individual receiver stations, and automatic tuning means for the oscillators at the receiver stations keeping the very high oscillator frequency controlled within close limits by means responsive to low frequency synchronization pulses transmitted on the video signals from the transmitting station.
2a ~,7~ ~3~
A still further aspect of the invention pertains to a bi-directional transmitter-receiver system that transmits information from a receiver site to a transmitter site by way of wireless transmission of an unmodulated pulse of precisely controlled frequency from a radio frequency oscillator. The improvement in the system comprises in combination, a radio : frequency oscillator at the receiver for transmitting the pulse and having a controlled oscillation frequency of a predetermined plurality of megahertz and frequency control means to maintain the oscillation frequency at the receiver site within a predetermined accuracy. The frequency control means comprises means at the transmitter site to generate and transmit to the receiver site synchronizing signals accurately controlled in frequency, gating means at the receiver site to derive from received synchronizing signals an accurately timed gating period, a counter to count oscillations from the oscillator at the receiver site for the time gating period, means to periodically reset the counter and repeat the count, and automatic frequency control means responsive to variations of counts produced by the counter over the counting period from a predetermined datum count representative of a desired oscillator frequency, thereby to correct any changes of the oscillator frequency at the receiver site from the desired frequency, whereby accurate frequency control of the oscillator at the receiver site is achieved over variations of voltage, temperature, aging and the like without crystal circuits.
More particularly, this invention provides an automatic frequency control circuit capable 2b 3 5~
of keeping a large number of multlple meyahertz transmittlng osclllators at receiver stations ln a TV answer back system accurately on frequency wlthln very close tolerances by synchronlzatlon with very low fre~uency vertical and horizontal sync pulses accurately t~rned and controled at TV
transmitter statlon and received an~ processed ln the same mlcroprocessor equipment at the receiver statlon used to process the tlming of transmisslon of answer back pulses.
To control the osclllator output with accuracles of a few parts per mlllion the osclllator output ls rnonltored by a counter that counts o .osclllations over a preclsely tlmeci Interval related to the accuracy of the studio generated vertical and ~orlzontal slgnals. T~us for a count lnterval of one second or a fraction of a second the number of osclllator cycles can be compared wlth a datum count or the exact expected count w~en on frequency and dlfferences are use~ to yenerate a corresponding correctlon signal in an automatic frequency control circuit.
The timlng conlrol accuracy Is obtalned in part by countlng vertical and horlzontal sync pulses transmitted frorn lhe I V transrnltter studlo to set a time perlod for gatlng count time for the oscillator output but rnore importantly by accurately tirnlng the beginning and ending tlrlle of the countlng period precisely at the occurrence of the leadirig ecige of the horizontal sync pulse.
Even further protectlon in t~e answer back system Is provlded by swltching clrcults preventing any transmlsslon from the recelver statlon unless the oscillator is on fre~uency. Thus wlthout a local crystal osclllator and wlthout any substantial extra equlprnent at tlle recelver r~
statlon, the iJac~ translrllsslon i~and Is kep~ very n3rl0w ~o wltl)ln a few parts per mlllion of the accurate studio source of vertlcal and horlzontal slgnals.
Also, by using the exlsting digltal encoding capabilitles at the ~; transmltter slte, and the data i~it receptlon capaiJIIItles already exlstlny at recelver locations, the datum count or the deslred answer back frequency from whlch the datum count can be derlved, can be sent from tt)e transmitter slte to the recelver statlon. Thus, tl)e answer back ~requency can be set and varied at will from the transmltter site. This Is very o important, as frequency avallabllity may vary rrom one locatlon lo another or may chanye wlth tlme, and dlfferent back frequencles may be deslred for each transmitter statlon.
In a TV answer back system where queries are encoded and thus become part of the vldeo slgnal, Is very Important that the equlpment at receivlng 15 statlons can dlscrlmlnate a true llve broadcast from a horl~e recordlng of a llve broadcast, as both program contents may contaln query s~gnals orderln~q receivlng statlons to transrnlt answer back pulses to the transmltter slte, It Is thus Important to prevent stations from respondlng to home recorded slgnals, as thls may Interfere with answers from true 20 llve query slgnals. Thls ls even more Important when the answer back frequency is controlled by the timlng of vertlcal and norlzontal sync pulses that when comlng from a l~ome vldeo recorder rnay produce not only false tlming of answer pulses, but an answer back carrier frequency under control of an unstable home video recorder.
25 The solutlon to t~ls problem Is to llave translrlltter TV statlons wlth query encoding capabillty encode tne real tlme (I.e. year, date, hours, minutes and seconds) of broadcast on all TV slgnals contalning querles and to have recelver s~3~io~s c()~ )al e ~l~ls i~l oa(Jcasl ~ e wltl~ tlllle Informatlon from a local battery backed clock source at eac~ receiver station If the dlrference between lhese two llrrles Is zero or less than a . few seconds the video source wlll be assumed to be llve and the battery backed clock wlll be updated thus kceplng recelver clock always In close 5 synchrony wlth the clock at t~e transmlsslon slle also the tlme of the last clock update wlll be stored In non volatile memory If the dlfference is more than a few seconds then thls ~Ifference wlll be dlvlded by the tlme elapsed between the last clock update and the current local clock tlme thus co~nputlng an error rate If thls error rate Is less than the expected error rate oF the receiver clock I.e. 100 parts per rnllllon then the source wlll be assumed to be a live broadcast and the clock wlll be updated otherwlse the source wlll be assumed to be a home recorded broadcast and the switchlng clrcuits to prevent transmlsslon from the recelver statlon wlll be actlvated.
Further features advantages and detalls of the lnventlon are set forth ln the followlng descrlptlon drawlngs and clalms.
DETAILED DE5CI~IPTION OF l-HE DI~AWINGS:
In the varlous vlews of the drawings Flgure l ls a systern block dlayrarn of t~)e bldlrectlonal transpondlng TV
20 systern embodylng the Invention In wh~ch an answer back ~rom any one of the many recelving statlons Is sent to a transrnltter studlo on an rf beep transrnlsslon of a preclse carrler frequency. One of the recelver statlons is shown wlth a functlonal diagrarn or the automatlc frequency control means afforded by tl~ls Inventlon ~or tl~e oscllla~or generatlng tlle carrler 25 frequency of answer beeps and with a furictional dlagram of the vldeo source dlscrlmlnatlon system k) prevent false answer beeps frorn belng transm!tted In response to vldeo recor(llnys or query encoded broadcasts Flgure 2 Is a wave forr~ dlagram sr~owlny ll~e nature of ll)e preclse . .
CONTROL OF RF PULSES_IN A rv ANSWER BACK SYSTEM
I ECI-IN I C~L i- I ELI):
This inventlon relates to TV answer back systems whereln rf answer 5pulses are transmltted rrOm recelver locatlons to TV studlos In response t to querles sent from TV studlos on the TV siynal, and more partlcularly It relates to the control of the carrier frequency at wh~ch the rf pulses are generated at the recelver locations, and to tl~e control and preventlon of false answer pulses from belng transmltted from recelver locatlons In 10response to querles recelved from a playback of a vldeo recordlng of a broadcast TV slgnal.
B~\CKGROUND ART:
In the TV answer back system of our U.S. Patent 4,591,906 i~ay 27, 1986 for Wireless Transmission from the Televlslon Set to the Televlslon 15Statlon, rf beep answers are transmltted by wlreless transrnlsslon from receiver statlons at very hlgh frequenciessuchas 53 megahertz or hlgher.
In thls system all receivers are operatlng on tl~e same answer back frequency. It ~s Imperatlve then that all the receivers have very carefully controlled answer back frequency to provlde a very narrow bandwldth 20necessary for the communlcatlo!) channel, and to assure tl~at all answers are recelved and processed at tl~e TV studlo. One means of control Is to provlde temperature compensated or oven crystal controlled osclllators at each recelver statlon. However, for mal-y thousand statlons In tl~e range of a slngle TV transmitter, tl~ls Is an expensive and unrellable undertaklng as 25shocks, aglng, and other factors that affect oscillatlon frequency can not be controlled In a l~ome envlroment.
Also, In a given geographlcal area, several TV slgnals ~rom TV statlons and ca~le channels may request answers slmult3ne()usly, and recelver ~ ~ ~, 2 .~?,..~
stations with capablllty to answer back In two or more fre~uer)cels rrlay i e deslrable. Accordlngly It Is an obJective of thls Inventlon to provlde Inexpenslve and accurate control of osclllators locate(J at recelver stations, in systems wlth slngle or multlple answer back frequencles.
The foregoing obJective ralses a serlous problem, namely that a very hlgll mult~ple megahertz oscillation frequency need be accurately frequency controlled wlthout crystals in a home envlronment where temperatures, voltages and other operatlonal conditlons vary slgnlficantly, ther~by t~nding to vary the oscillator frequency.
It is also deslrable to have a frequency control system compatible with the technology used in the answer back equipment In order to further reduce cost. Thus, the use of pulse countiny microprocessor technology Is preferred. Thls then raises a problem that heretofore has not been resolved.
.. namely it does not seem possible to control the megahertz osclllator frequency accurately withln very few parts per rnilllon wlthout havlng local means to control the enYironment (as In oven crystals), or to : ` compensate for changes In amblent codltlons (temperature compensation), or to adJust for changes due to aglng ( manual screw adJustments).
In a TV answer back system where TV statlons encode query slgnals Into the vl(;ieo slynal"~ecelver slatlor)s sen~i rf answer pulses In resf~onse to querles contalned In the vldeo slgnal, however, recelver statlons wlll also send rf answer pulses In response to a vldeo slgnal comlng from a home vldeo recorder when tl~is slgnal was orlyinaly recorded frorn a TV
broadcast contalnlng encoded querles. Tl~is tl~en ralses a problell) that heretofore l~as not been resolved, naloely it does not seem possible to discrlmlnate from a live TV slgnal containing ~uerles and from a home vldeo recording of a TV slgnal containil-g ~lueries, and thus pl event recelver statlons from sending rf answer pulses th3t may Intel fere with . .
. ~ ' t'3 L;3 ~ S;j r~ l~ .J ~ ,J
answers from live broadcast queries.
DISCLOSURE OF THE INVENTION: . r Accordingly, the invention in one broad aspect pertains to a television system having a plurality of television receiver 5 stations operable to reproduce multiple live and recorded television signals from various sources wherein there is apparatus for distinguishing receiver operation in response to live and recorded signal sources. The apparatus comprises in combination means at a television transmitting station for lO accurately controlling a time signal and transmitting it on a live television signal, means operable to receive the time signal at a television receiving station, and detection means at the receiver station for comparing the received transmitter time signal with a time signal being produced at the receiving station 15 to determine when a live broadcast is being reproduced.
Another aspect of the invention comprehends a television transponder system having a plurality of television receiver stations capable of sending information in response to a viewer's response to a querying television transmitting studio which is 20 transmitting queries to receivers on video signals. The system comprises in combination, transmitters at all the receiver stations having oscillators for transmitting respectively on a single very high transmission frequency of a predetermined number of megahertz unmodulated pulses at precise times for identifying 25 individual receiver stations, and automatic tuning means for the oscillators at the receiver stations keeping the very high oscillator frequency controlled within close limits by means responsive to low frequency synchronization pulses transmitted on the video signals from the transmitting station.
2a ~,7~ ~3~
A still further aspect of the invention pertains to a bi-directional transmitter-receiver system that transmits information from a receiver site to a transmitter site by way of wireless transmission of an unmodulated pulse of precisely controlled frequency from a radio frequency oscillator. The improvement in the system comprises in combination, a radio : frequency oscillator at the receiver for transmitting the pulse and having a controlled oscillation frequency of a predetermined plurality of megahertz and frequency control means to maintain the oscillation frequency at the receiver site within a predetermined accuracy. The frequency control means comprises means at the transmitter site to generate and transmit to the receiver site synchronizing signals accurately controlled in frequency, gating means at the receiver site to derive from received synchronizing signals an accurately timed gating period, a counter to count oscillations from the oscillator at the receiver site for the time gating period, means to periodically reset the counter and repeat the count, and automatic frequency control means responsive to variations of counts produced by the counter over the counting period from a predetermined datum count representative of a desired oscillator frequency, thereby to correct any changes of the oscillator frequency at the receiver site from the desired frequency, whereby accurate frequency control of the oscillator at the receiver site is achieved over variations of voltage, temperature, aging and the like without crystal circuits.
More particularly, this invention provides an automatic frequency control circuit capable 2b 3 5~
of keeping a large number of multlple meyahertz transmittlng osclllators at receiver stations ln a TV answer back system accurately on frequency wlthln very close tolerances by synchronlzatlon with very low fre~uency vertical and horizontal sync pulses accurately t~rned and controled at TV
transmitter statlon and received an~ processed ln the same mlcroprocessor equipment at the receiver statlon used to process the tlming of transmisslon of answer back pulses.
To control the osclllator output with accuracles of a few parts per mlllion the osclllator output ls rnonltored by a counter that counts o .osclllations over a preclsely tlmeci Interval related to the accuracy of the studio generated vertical and ~orlzontal slgnals. T~us for a count lnterval of one second or a fraction of a second the number of osclllator cycles can be compared wlth a datum count or the exact expected count w~en on frequency and dlfferences are use~ to yenerate a corresponding correctlon signal in an automatic frequency control circuit.
The timlng conlrol accuracy Is obtalned in part by countlng vertical and horlzontal sync pulses transmitted frorn lhe I V transrnltter studlo to set a time perlod for gatlng count time for the oscillator output but rnore importantly by accurately tirnlng the beginning and ending tlrlle of the countlng period precisely at the occurrence of the leadirig ecige of the horizontal sync pulse.
Even further protectlon in t~e answer back system Is provlded by swltching clrcults preventing any transmlsslon from the recelver statlon unless the oscillator is on fre~uency. Thus wlthout a local crystal osclllator and wlthout any substantial extra equlprnent at tlle recelver r~
statlon, the iJac~ translrllsslon i~and Is kep~ very n3rl0w ~o wltl)ln a few parts per mlllion of the accurate studio source of vertlcal and horlzontal slgnals.
Also, by using the exlsting digltal encoding capabilitles at the ~; transmltter slte, and the data i~it receptlon capaiJIIItles already exlstlny at recelver locations, the datum count or the deslred answer back frequency from whlch the datum count can be derlved, can be sent from tt)e transmitter slte to the recelver statlon. Thus, tl)e answer back ~requency can be set and varied at will from the transmltter site. This Is very o important, as frequency avallabllity may vary rrom one locatlon lo another or may chanye wlth tlme, and dlfferent back frequencles may be deslred for each transmitter statlon.
In a TV answer back system where queries are encoded and thus become part of the vldeo slgnal, Is very Important that the equlpment at receivlng 15 statlons can dlscrlmlnate a true llve broadcast from a horl~e recordlng of a llve broadcast, as both program contents may contaln query s~gnals orderln~q receivlng statlons to transrnlt answer back pulses to the transmltter slte, It Is thus Important to prevent stations from respondlng to home recorded slgnals, as thls may Interfere with answers from true 20 llve query slgnals. Thls ls even more Important when the answer back frequency is controlled by the timlng of vertlcal and norlzontal sync pulses that when comlng from a l~ome vldeo recorder rnay produce not only false tlming of answer pulses, but an answer back carrier frequency under control of an unstable home video recorder.
25 The solutlon to t~ls problem Is to llave translrlltter TV statlons wlth query encoding capabillty encode tne real tlme (I.e. year, date, hours, minutes and seconds) of broadcast on all TV slgnals contalning querles and to have recelver s~3~io~s c()~ )al e ~l~ls i~l oa(Jcasl ~ e wltl~ tlllle Informatlon from a local battery backed clock source at eac~ receiver station If the dlrference between lhese two llrrles Is zero or less than a . few seconds the video source wlll be assumed to be llve and the battery backed clock wlll be updated thus kceplng recelver clock always In close 5 synchrony wlth the clock at t~e transmlsslon slle also the tlme of the last clock update wlll be stored In non volatile memory If the dlfference is more than a few seconds then thls ~Ifference wlll be dlvlded by the tlme elapsed between the last clock update and the current local clock tlme thus co~nputlng an error rate If thls error rate Is less than the expected error rate oF the receiver clock I.e. 100 parts per rnllllon then the source wlll be assumed to be a live broadcast and the clock wlll be updated otherwlse the source wlll be assumed to be a home recorded broadcast and the switchlng clrcuits to prevent transmlsslon from the recelver statlon wlll be actlvated.
Further features advantages and detalls of the lnventlon are set forth ln the followlng descrlptlon drawlngs and clalms.
DETAILED DE5CI~IPTION OF l-HE DI~AWINGS:
In the varlous vlews of the drawings Flgure l ls a systern block dlayrarn of t~)e bldlrectlonal transpondlng TV
20 systern embodylng the Invention In wh~ch an answer back ~rom any one of the many recelving statlons Is sent to a transrnltter studlo on an rf beep transrnlsslon of a preclse carrler frequency. One of the recelver statlons is shown wlth a functlonal diagrarn or the automatlc frequency control means afforded by tl~ls Inventlon ~or tl~e oscllla~or generatlng tlle carrler 25 frequency of answer beeps and with a furictional dlagram of the vldeo source dlscrlmlnatlon system k) prevent false answer beeps frorn belng transm!tted In response to vldeo recor(llnys or query encoded broadcasts Flgure 2 Is a wave forr~ dlagram sr~owlny ll~e nature of ll)e preclse . .
2 ~ r~ ~ ~ ~J ~`~
tlmln~ slgnals for the col~trol of tl)c o~clllator ~ J~l~cy as affor-Je(J by ll)ls Inventlon, Flyure 3 Is clrcult block dlagralll of a mlcroprocessol ~ased Irnplelnentatlol~ of tl~e answer ~3ck system a~ e recelver stallol~s wl~lcl 5 embody the Inventlon, Figure 4 Is a flow dlagram of tlle software implernented on the mlcroprocessor of Flgure 3 ~or the automatlc frequency control afforded by thls Invention., Figure 5 Is a flow diagram of the software Implemented on the lG microprocessor of Flgure 3 for the video source dlscrlmlnatlon afforded by thls Inventlon.
THE PI~EFEI~RED EMBODIMENT:
The TV answer back system embodying thls Invention l)as a TV statlon ~ with a vldeo source 2 havlng a carefully controlled oven crystai sync 15 source 1, the slgnal generated by the vldeo source Is encoded wlth dlgltal querles and other dlgltal Informatlon by dlgltal data encoder 4 whlch Is under control of control computer 5, the video slgnal modlfled by dlgltal data encoder Is then rf modulated and amplified by 6and transmitted on antenna 7 to a plurallty of recelver statlons 8a, ~b,...8x, etc. As set forth 20 in our patent query signals may be transrnitted from TV statlon 3 and answer signals sent back from t~)e Indivl~lual recelver statlons, ~a,...etc. In the form of rf pulses. All tl~e rf pulses are at the same fre~uency to produce response from all the receiver statlons wltl)ln a narrow band, typlcally at a VHF carrler frequency of 53 to 220 megal~ertz. Eacl~ recelver 25 statlon Is Identlfle~J by a partlcular tlme of transllllsslon Or an rf pulse located accurately along one of the horlzontal lines of a vldeo frame.
Thus the receiver statlon ~x has a local osclllator 11 and an rf pulse amplirler 10 for transmltting on antenna ~, arl(~ a recelvlng antellna 13 with ~ recelver ~nd demodulator 1 ~ t g~nerat~ ~ con~l)oslte vl(Jeo slgn~l .22 whlcl~ls decol~posedbysyncan~ ~ala se~arator ~ I Inlo ver~lcal sync - signal 20 horlzontal sync slgnal 19 and decoded data siynal 18 I llcroprocessor and control clrcult 13 process (~Igltal querles fr()~ V
5 statlon contained in data slgnal 18 and formulate and time the transmlsslon of response rf pulses wlth carrler frequency from osclllator 1 1 .
In accordance wltl~ thls inventlon that equlpment Is used for the purpose of controliing the frequency of osclllator 11 wlthln close !Imlts in an automatlc frequency control (AFC) systern 13 In response to vldeo sjync pulses generated at the TV statlon 3 and received at the receiver seation 8x The AFC system 13 conlprlses a counter 14 which responds to osclllatlons from lead 15 representatlve of osclllatlons from VHF
osc)llator 11 as modlfied by optlonal prescaler 16 that dlvldes the 15 osclllation frequency of 11 to a lower ~requency rnore adequate for counter 14 output from prescaler 16 Is gated at gate 2~ by gatlng tlme slgnal 30 to control osclllatlon count over a carefully controlled sampling tlme determlned at gatlng control 32 by tlle vldeo vertlcal 20 and horlzontal 19 sync pulses derlved from tl~e recelve~l vldeo slgnal22. An automatlc frequency correction slgnal 23 Is derived by clrcult 24 by comparlson of the count sample in counter 14 with tl~e deslred datum count In latch 25 representative of tl~e exact ~eslred frequency of oscillator 11 The deslred datum count rnay be set at TV statlon 3 by an operator throuyh control colnputer 5 and dlgitally encoded Into the TV
slgnal by encoder 4 the transn~ltted data wlll ~e recelved at recelver statlon 8x and wlll be latclled by circuit 25from decoded data slgnal 18 It Is posslble to obtalnvery good accuracy of tl~e VHF osclllator 11 wlth the low frequency vertlcal and l~orizontal syncl~ronlzatlon pulses by ~ ~ -J ~ J ~ J
means of tl~e and gate 26 In t~e l~la~ er Illustrate~ l~y the waveforlns of Figure 2. The l~orizontal an(l vertical sync pulses in tl~e vldeo signal transmitted from the TV statlon are carerully tlmed and controlled for close accuracy, and tllls tlll)ln(3 Is use(l to rep~ace ~l~e cryslal cuntrol 5 clrcults at the recelver statlon. First a reset slgnal 31 Is generated to reset counter 14 to zer(), after tl~at, a preclsely tll~le(J gatln(~ perl()d 30 Is produced by gatlng control clrcult 32, gatlny perlo~ 30 preclsely gates counts o~ osclllator 11 as modified by optlonal prescaler (frequency dlvlder) 16. If the resulting count Is Identlcal to the datun~ count 25, tl~e o osclllator ls on frequency and no correctlon Is necessary In AFC slgnal 23.
If the count Is not Identlcal a frequency control slgnal 23 will be generated, and If the erroristoolargeslgnal ~5 wlll actlvate swltch 4~ to prevent transrnlsslon of out of ban~ rf pulses. Tl~e gatlng perlod Is a function of tl~e desired accuracy of the osclllator and of the actual 15 accuracy of the vertlcal and horlzontal sync pulses, as shown on Flgure 2, it may be typicallythetenth of a second as determlned by a count of slx vertical sync pulses by gatlng control 32, wl~ere in response to the leadlng edge of the flrst horizontal sync pulse followlng a vertlcal pulse the gatlng period Is started and termlnated. In this manner tlle gatlng perlod 20 30 may be accurately repeated and tl~e osclllator frequency may be controlled wlti~ln very close llmlts to a deslred frequency.
On Flgure I recelver statlon 8x also comprlses a vldeo dlscrlmlnator system 60 for the purpose of discrlmlnating a true llve broadcast slgnal from a l~ome recordlng of a llve broa~cast, tl~us preventlng answer pulses 25 fr~m belng transrnltted In response to queries contalned In i~ome recordings. Dlscrlminator 60 Is comprlse(J of latci~ 61 ~l~lci~ latcl~es broadcast tlme informatlon encoded Into tl)e vldeo slgnal ~y contl ol cornputer 5 at TV statlon 3, tl~is time information Is received at station ~ 2 ~
ax and decoded as ~iata slgnal 1~3 ~Ime In~()r~l~a~ rrom 61 Is c()~ e~ at circult 62 with tlrne from battery backed local clock 63 and a time error Is computed If the error Is cero or less than a few seconds local ciock 63 wlll be updated and tl~e tlme of tl)ls upda~e wlll lJe slored In norlvolatlle 5 memory 64 If the error is more than a few seconds the error Is dlvlded by the tlme elapsed between the last clock upda~e contalned In merrlory 64 and tl~e iocal clock tlme 63 tl~us an error rate wlll be computed If this error rate Is less than the e~pected error rate of tl)e local clock I e 100 parts per milllon then the vldeo source wlll be assumed to be a llve o broadcast and the local clock 6~ wlll be updated wlth tlme from 61 otherwise the video source wlll be assumed to be a prevlously recorded broadcast and the swltchlng clrcuits 4~ will be activated by slgl)al 65 to prevent transmisslon of answers In response to recorded querles Figure 3 shows a microprocessor based implementatlon of the 15 prevlously descrlbed functlons of tl~ls Invenllon fl~ flop 73 Is used to preclsely generate gating tlme 30 to start and end at preclsely the leadlng edge (lo-hl transitlon) of the horlzontal sync signal 19 as described by software flow dlagram of Flgure 4 ON slgnal 71 and OFF slgnal 72 are software drlven to start gatlng tlme 30 at tl~e flrst horlzontal sync 20 followlng a vertlcal sync pulse and to en~i gatlng tlrl~e 30 at the flrst horlzontal sync slx vel~tlcal sync pulses laler Reset slynal 31 Is also software generated to periodically clear counter 14 ~efore a new count cycle begins datum 25 Is read and latched by microprocessor q3 software and periodlcally cornpared with counter 14 coun~ fr()m thls cornparlson an 25 error Is computed that Is used to correct tl~e digltal input to dlgltal to analog conveter (DAC) 70 whose analog output 23 drives voltage contl ol led oscl l lator I i The software flow dlagraln or Flgure 5 descrlbes l~ow the vldeo ~iscrlmination function 60 is impler7lented on the microprocessor based Implementatlol) of Fl~ure 3. As ,~)revlou~ly ~Jescril)ed, ll~e software ~
compare If the broadcast tlme Informatlon enco(~ed on the vldeo slgnal Is e~luai to or wlthln an error rate ur tl,e tll-lle rl o~n ll~e local clock source 63.
If this is the case the video source Is a live broadcast, SWItCh 48 wlll be c l osed to a l l ow transmission Or answ er pu l ses, the l oca l c l ock w l l l be updated and the tlme of tl~is update will be stored in non-volatlle memory 64 for future use In computlng clock error rate. Otherwlse, the vldeo source Is a home recorded broadcast and swltch 48 wlll be opened to o prevent false answer pulses to be transmltted In response to querles received from a recorded vldeo slgnal In the forgolng manner therefore the bidirectional TV answer back system provides at a multlpllclty or receivers precise control of answer back transmlsslon carrier frequency wlthout the necessity for accurate crystal control of the local osclllators, ~t also prevents answers frorn being transmltted In response to querles from playbacks of home vldeo recordlngs that could Interfere wlth true llve query broadcasts and could a!so have out of band carrler frequency as local osclllator would synchronl~e In response to sync slgnals from unstable home vldeo recorders. The invention provldes a l~lgl~ accuracy of control of very hlgh frequency osclllators unexpectedly wlth very low low frequency slgnals that can be handled In conventlonal microprocessor clrcults and thus permlts recelver statlons to comply wltl- strlct frequency varlatlon standards for transmlsslon of rf slgnals under condltlons not as controllable as those In TV transmltting studios. Also, the Inventlon gaurantees that recelver statlons wlll only transrnlt answer back pulses In response to true llve broadcasts, an Indlspensal~le condltlon to obtaln llcense permlts to operate several thousand transmltters at recelver l ~ fJ ? ~
tatlons. Thus the state of tl~e art Is a(~vance~ and tnose features of novelty descrlptive of the spirlt and tl)e natul-e of the Inventlon are set forth with partlcularity In tl~e followlng clalrns.
~5 .. .
~5
tlmln~ slgnals for the col~trol of tl)c o~clllator ~ J~l~cy as affor-Je(J by ll)ls Inventlon, Flyure 3 Is clrcult block dlagralll of a mlcroprocessol ~ased Irnplelnentatlol~ of tl~e answer ~3ck system a~ e recelver stallol~s wl~lcl 5 embody the Inventlon, Figure 4 Is a flow dlagram of tlle software implernented on the mlcroprocessor of Flgure 3 ~or the automatlc frequency control afforded by thls Invention., Figure 5 Is a flow diagram of the software Implemented on the lG microprocessor of Flgure 3 for the video source dlscrlmlnatlon afforded by thls Inventlon.
THE PI~EFEI~RED EMBODIMENT:
The TV answer back system embodying thls Invention l)as a TV statlon ~ with a vldeo source 2 havlng a carefully controlled oven crystai sync 15 source 1, the slgnal generated by the vldeo source Is encoded wlth dlgltal querles and other dlgltal Informatlon by dlgltal data encoder 4 whlch Is under control of control computer 5, the video slgnal modlfled by dlgltal data encoder Is then rf modulated and amplified by 6and transmitted on antenna 7 to a plurallty of recelver statlons 8a, ~b,...8x, etc. As set forth 20 in our patent query signals may be transrnitted from TV statlon 3 and answer signals sent back from t~)e Indivl~lual recelver statlons, ~a,...etc. In the form of rf pulses. All tl~e rf pulses are at the same fre~uency to produce response from all the receiver statlons wltl)ln a narrow band, typlcally at a VHF carrler frequency of 53 to 220 megal~ertz. Eacl~ recelver 25 statlon Is Identlfle~J by a partlcular tlme of transllllsslon Or an rf pulse located accurately along one of the horlzontal lines of a vldeo frame.
Thus the receiver statlon ~x has a local osclllator 11 and an rf pulse amplirler 10 for transmltting on antenna ~, arl(~ a recelvlng antellna 13 with ~ recelver ~nd demodulator 1 ~ t g~nerat~ ~ con~l)oslte vl(Jeo slgn~l .22 whlcl~ls decol~posedbysyncan~ ~ala se~arator ~ I Inlo ver~lcal sync - signal 20 horlzontal sync slgnal 19 and decoded data siynal 18 I llcroprocessor and control clrcult 13 process (~Igltal querles fr()~ V
5 statlon contained in data slgnal 18 and formulate and time the transmlsslon of response rf pulses wlth carrler frequency from osclllator 1 1 .
In accordance wltl~ thls inventlon that equlpment Is used for the purpose of controliing the frequency of osclllator 11 wlthln close !Imlts in an automatlc frequency control (AFC) systern 13 In response to vldeo sjync pulses generated at the TV statlon 3 and received at the receiver seation 8x The AFC system 13 conlprlses a counter 14 which responds to osclllatlons from lead 15 representatlve of osclllatlons from VHF
osc)llator 11 as modlfied by optlonal prescaler 16 that dlvldes the 15 osclllation frequency of 11 to a lower ~requency rnore adequate for counter 14 output from prescaler 16 Is gated at gate 2~ by gatlng tlme slgnal 30 to control osclllatlon count over a carefully controlled sampling tlme determlned at gatlng control 32 by tlle vldeo vertlcal 20 and horlzontal 19 sync pulses derlved from tl~e recelve~l vldeo slgnal22. An automatlc frequency correction slgnal 23 Is derived by clrcult 24 by comparlson of the count sample in counter 14 with tl~e deslred datum count In latch 25 representative of tl~e exact ~eslred frequency of oscillator 11 The deslred datum count rnay be set at TV statlon 3 by an operator throuyh control colnputer 5 and dlgitally encoded Into the TV
slgnal by encoder 4 the transn~ltted data wlll ~e recelved at recelver statlon 8x and wlll be latclled by circuit 25from decoded data slgnal 18 It Is posslble to obtalnvery good accuracy of tl~e VHF osclllator 11 wlth the low frequency vertlcal and l~orizontal syncl~ronlzatlon pulses by ~ ~ -J ~ J ~ J
means of tl~e and gate 26 In t~e l~la~ er Illustrate~ l~y the waveforlns of Figure 2. The l~orizontal an(l vertical sync pulses in tl~e vldeo signal transmitted from the TV statlon are carerully tlmed and controlled for close accuracy, and tllls tlll)ln(3 Is use(l to rep~ace ~l~e cryslal cuntrol 5 clrcults at the recelver statlon. First a reset slgnal 31 Is generated to reset counter 14 to zer(), after tl~at, a preclsely tll~le(J gatln(~ perl()d 30 Is produced by gatlng control clrcult 32, gatlny perlo~ 30 preclsely gates counts o~ osclllator 11 as modified by optlonal prescaler (frequency dlvlder) 16. If the resulting count Is Identlcal to the datun~ count 25, tl~e o osclllator ls on frequency and no correctlon Is necessary In AFC slgnal 23.
If the count Is not Identlcal a frequency control slgnal 23 will be generated, and If the erroristoolargeslgnal ~5 wlll actlvate swltch 4~ to prevent transrnlsslon of out of ban~ rf pulses. Tl~e gatlng perlod Is a function of tl~e desired accuracy of the osclllator and of the actual 15 accuracy of the vertlcal and horlzontal sync pulses, as shown on Flgure 2, it may be typicallythetenth of a second as determlned by a count of slx vertical sync pulses by gatlng control 32, wl~ere in response to the leadlng edge of the flrst horizontal sync pulse followlng a vertlcal pulse the gatlng period Is started and termlnated. In this manner tlle gatlng perlod 20 30 may be accurately repeated and tl~e osclllator frequency may be controlled wlti~ln very close llmlts to a deslred frequency.
On Flgure I recelver statlon 8x also comprlses a vldeo dlscrlmlnator system 60 for the purpose of discrlmlnating a true llve broadcast slgnal from a l~ome recordlng of a llve broa~cast, tl~us preventlng answer pulses 25 fr~m belng transrnltted In response to queries contalned In i~ome recordings. Dlscrlminator 60 Is comprlse(J of latci~ 61 ~l~lci~ latcl~es broadcast tlme informatlon encoded Into tl)e vldeo slgnal ~y contl ol cornputer 5 at TV statlon 3, tl~is time information Is received at station ~ 2 ~
ax and decoded as ~iata slgnal 1~3 ~Ime In~()r~l~a~ rrom 61 Is c()~ e~ at circult 62 with tlrne from battery backed local clock 63 and a time error Is computed If the error Is cero or less than a few seconds local ciock 63 wlll be updated and tl~e tlme of tl)ls upda~e wlll lJe slored In norlvolatlle 5 memory 64 If the error is more than a few seconds the error Is dlvlded by the tlme elapsed between the last clock upda~e contalned In merrlory 64 and tl~e iocal clock tlme 63 tl~us an error rate wlll be computed If this error rate Is less than the e~pected error rate of tl)e local clock I e 100 parts per milllon then the vldeo source wlll be assumed to be a llve o broadcast and the local clock 6~ wlll be updated wlth tlme from 61 otherwise the video source wlll be assumed to be a prevlously recorded broadcast and the swltchlng clrcuits 4~ will be activated by slgl)al 65 to prevent transmisslon of answers In response to recorded querles Figure 3 shows a microprocessor based implementatlon of the 15 prevlously descrlbed functlons of tl~ls Invenllon fl~ flop 73 Is used to preclsely generate gating tlme 30 to start and end at preclsely the leadlng edge (lo-hl transitlon) of the horlzontal sync signal 19 as described by software flow dlagram of Flgure 4 ON slgnal 71 and OFF slgnal 72 are software drlven to start gatlng tlme 30 at tl~e flrst horlzontal sync 20 followlng a vertlcal sync pulse and to en~i gatlng tlrl~e 30 at the flrst horlzontal sync slx vel~tlcal sync pulses laler Reset slynal 31 Is also software generated to periodically clear counter 14 ~efore a new count cycle begins datum 25 Is read and latched by microprocessor q3 software and periodlcally cornpared with counter 14 coun~ fr()m thls cornparlson an 25 error Is computed that Is used to correct tl~e digltal input to dlgltal to analog conveter (DAC) 70 whose analog output 23 drives voltage contl ol led oscl l lator I i The software flow dlagraln or Flgure 5 descrlbes l~ow the vldeo ~iscrlmination function 60 is impler7lented on the microprocessor based Implementatlol) of Fl~ure 3. As ,~)revlou~ly ~Jescril)ed, ll~e software ~
compare If the broadcast tlme Informatlon enco(~ed on the vldeo slgnal Is e~luai to or wlthln an error rate ur tl,e tll-lle rl o~n ll~e local clock source 63.
If this is the case the video source Is a live broadcast, SWItCh 48 wlll be c l osed to a l l ow transmission Or answ er pu l ses, the l oca l c l ock w l l l be updated and the tlme of tl~is update will be stored in non-volatlle memory 64 for future use In computlng clock error rate. Otherwlse, the vldeo source Is a home recorded broadcast and swltch 48 wlll be opened to o prevent false answer pulses to be transmltted In response to querles received from a recorded vldeo slgnal In the forgolng manner therefore the bidirectional TV answer back system provides at a multlpllclty or receivers precise control of answer back transmlsslon carrier frequency wlthout the necessity for accurate crystal control of the local osclllators, ~t also prevents answers frorn being transmltted In response to querles from playbacks of home vldeo recordlngs that could Interfere wlth true llve query broadcasts and could a!so have out of band carrler frequency as local osclllator would synchronl~e In response to sync slgnals from unstable home vldeo recorders. The invention provldes a l~lgl~ accuracy of control of very hlgh frequency osclllators unexpectedly wlth very low low frequency slgnals that can be handled In conventlonal microprocessor clrcults and thus permlts recelver statlons to comply wltl- strlct frequency varlatlon standards for transmlsslon of rf slgnals under condltlons not as controllable as those In TV transmltting studios. Also, the Inventlon gaurantees that recelver statlons wlll only transrnlt answer back pulses In response to true llve broadcasts, an Indlspensal~le condltlon to obtaln llcense permlts to operate several thousand transmltters at recelver l ~ fJ ? ~
tatlons. Thus the state of tl~e art Is a(~vance~ and tnose features of novelty descrlptive of the spirlt and tl)e natul-e of the Inventlon are set forth with partlcularity In tl~e followlng clalrns.
~5 .. .
~5
Claims (12)
1. In a bi-directional transmitter-receiver system that transmits information from a receiver site to a transmitter site by way of wireless transmission of an unmodulated pulse of precisely controlled frequency from a radio frequency oscillator, the improvement comprising in combination, a radio frequency oscillator at the receiver for transmitting said pulse and having a controlled oscillation frequency of a predetermined plurality of megahertz and frequency control means to maintain the oscillation frequency at the receiver site within a predetermined accuracy, said means comprising:
means at the transmitter site to generate and transmit to the receiver site synchronizing signals accurately controlled in frequency, gating means at the receiver site to derive from re-ceived synchronizing signals an accurately timed gating period, a counter to count oscillations from the oscillator at the receiver site for the time gating period, means to periodically reset the counter and repeat the count, and automatic frequency control means responsive to variations of counts produced by the counter over the counting period from a predetermined datum count representative of a desired oscillator frequency thereby to correct any changes of the oscillator frequency at the receiver site from the desired frequency, whereby accurate frequency control of the oscillator at the receiver site is achieved over variations of voltage, temperature, aging and the like without crystal circuits.
means at the transmitter site to generate and transmit to the receiver site synchronizing signals accurately controlled in frequency, gating means at the receiver site to derive from re-ceived synchronizing signals an accurately timed gating period, a counter to count oscillations from the oscillator at the receiver site for the time gating period, means to periodically reset the counter and repeat the count, and automatic frequency control means responsive to variations of counts produced by the counter over the counting period from a predetermined datum count representative of a desired oscillator frequency thereby to correct any changes of the oscillator frequency at the receiver site from the desired frequency, whereby accurate frequency control of the oscillator at the receiver site is achieved over variations of voltage, temperature, aging and the like without crystal circuits.
2. A system as defined in claim 1 further comprising signal transmission means coupled to the oscillator at the receiver site to transmit signals from the receiver location, and switching means responsive to said counter to permit transmission of the signal only when the oscillator at the receiver site is at a frequency corresponding to the datum count.
3. A system as defined in claim 1 where the transmitter is a television transmitter further comprising, synchronization means for said gating means operable to count a period between an integral number of vertical sync signals.
4. A system as defined in claim 1 where the transmitter is a television transmitter further comprising, synchronization means for said gating means operable to count a period between an integral number of horizontal sync signals.
5. A system as defined in claim 1 wherein, said datum count is set by signals transmitted from the transmitter site and received at the receiver site, thus permitting variable control of the oscillator frequency at the receiver site from the oscillator at the transmitter site.
6. A television transponder system having a plurality of television receiver stations capable of sending information in response to a viewer's response to a querying television transmitting studio which is transmitting queries to receivers on video signals, comprising in combination, transmitters at all said receiver stations having oscillators for transmitting respectively on a single very high transmission frequency of a predetermined number of megahertz unmodulated pulses at precise times for identifying individual receiver stations, and automatic tuning means for said oscillators at the receiver stations keeping the very high oscillator frequency controlled within close limits by means responsive to low frequency synchronization pulses transmitted on the video signals from the transmitting station.
7. The system as defined in claim 6 wherein the oscillators are frequency controlled in the automatic tuning means by frequency control means comprising a periodically time gated counter of the oscillator output frequency, and further frequency control means responsive to variations in count from a datum count achieved when the oscillator output frequency is at its desired frequency.
8. The system of claim 7 wherein the time gated counter is gated between a predetermined number of vertical sync pulses derived from said video signals.
9. The system of claim 7 wherein the time gated counter is gated between a predetermined number of horizontal sync pulses derived from said video signals.
10. The system of claim 7 including switching means for preventing transmissions from the receiver stations when the oscillators thereat are not at the desired frequency.
11. The system of claim 6 further comprising means at the television transmitting studio for transmitting information on a desired receiver transmitting frequency and means at receiver stations for receiving such information, and where said oscillator and automatic tuning means at receiver stations are operable at different desired frequencies, thereby allowing receiver stations to send information to different television transmitter studios on different frequencies.
12. A television transponder system having a plurality of television receiver stations capable of sending information to a television transmitting studio which is transmitting video signals, comprising in combination, transmitters at all receiver stations for transmitting respectively on a single very high transmission frequency of a predetermined number of megahertz by means of oscillators for respectively transmitting pulses at precise times identifying individual receiver stations, automatic tuning means (claim 12 cont'd) for said oscillators at the receiver stations keeping the very high oscillator frequency controlled within close limits by means responsive to low frequency synchronization pulses transmitted on the video signals from the transmitting station and means for distinguishing receiver operation in response to live and recorded signal sources, comprising in combination, means at a television transmitting station for accurately controlling a time signal and transmitting it on a live television signal, means operable to receive said time signal at a television receiving station, and detection means at the receiver station for comparing the received transmitter time signal with a time signal being reproduced at the receiving station to determine when a live broadcast is being received.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/934,866 US4755871A (en) | 1986-11-25 | 1986-11-25 | Control of rf answer pulses in a TV answer back system |
| US934,866 | 1986-11-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1322592C true CA1322592C (en) | 1993-09-28 |
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ID=25466203
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000552649A Expired - Fee Related CA1322592C (en) | 1986-11-25 | 1987-11-24 | Control of rf pulses in a tv answer back system |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4755871A (en) |
| EP (1) | EP0269094B1 (en) |
| JP (1) | JPS63149975A (en) |
| AT (1) | ATE91583T1 (en) |
| CA (1) | CA1322592C (en) |
| DE (1) | DE3786529T2 (en) |
| ES (1) | ES2044895T3 (en) |
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| US4965825A (en) | 1981-11-03 | 1990-10-23 | The Personalized Mass Media Corporation | Signal processing apparatus and methods |
| USRE47642E1 (en) | 1981-11-03 | 2019-10-08 | Personalized Media Communications LLC | Signal processing apparatus and methods |
| US7831204B1 (en) | 1981-11-03 | 2010-11-09 | Personalized Media Communications, Llc | Signal processing apparatus and methods |
| DE3642629A1 (en) * | 1986-12-13 | 1988-06-23 | Grundig Emv | SYSTEM FOR PROCESSING ENCRYPTED TRANSFER INFORMATION |
| IL94519A (en) * | 1989-06-13 | 1993-07-08 | Tv Answer Int Inc | Satellite television communication system for audience polling and processing answers |
| US5101267A (en) * | 1989-08-07 | 1992-03-31 | Tv Answer, Inc. | Wide area real-time T-V audience polling system with local area stations linked by satellite |
| US5257099A (en) * | 1989-08-07 | 1993-10-26 | Tv Answer, Inc. | Central data processing station for satellite communication with local area audience response station |
| EP0551433B1 (en) * | 1990-10-01 | 2001-05-09 | BUSH, Thomas A. | Transactional processing system |
| US5519433A (en) * | 1991-11-20 | 1996-05-21 | Zing Systems, L.P. | Interactive television security through transaction time stamping |
| US6457177B1 (en) | 1992-05-01 | 2002-09-24 | Digitalconvergence.Com Inc. | Dual port interactive media system |
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| US3733430A (en) * | 1970-12-28 | 1973-05-15 | Rca Corp | Channel monitoring system |
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| IT1020803B (en) * | 1974-09-16 | 1977-12-30 | Rai Radiotelevisione Italiana | PROCEDURE AND DEVICE FOR THE BIDIRECTIONAL TRANSMISSION ITERATE GOES BETWEEN USERS AND HEAD STATION IN CABLE TELEVISION SYSTEMS |
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| US4591906A (en) * | 1986-02-12 | 1986-05-27 | Morales Garza Fernando | Wireless transmission from the television set to the television station |
-
1986
- 1986-11-25 US US06/934,866 patent/US4755871A/en not_active Expired - Fee Related
-
1987
- 1987-11-24 CA CA000552649A patent/CA1322592C/en not_active Expired - Fee Related
- 1987-11-25 JP JP62297305A patent/JPS63149975A/en active Pending
- 1987-11-25 EP EP87117414A patent/EP0269094B1/en not_active Expired - Lifetime
- 1987-11-25 DE DE87117414T patent/DE3786529T2/en not_active Expired - Fee Related
- 1987-11-25 ES ES87117414T patent/ES2044895T3/en not_active Expired - Lifetime
- 1987-11-25 AT AT87117414T patent/ATE91583T1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| DE3786529T2 (en) | 1994-02-17 |
| JPS63149975A (en) | 1988-06-22 |
| ES2044895T3 (en) | 1994-01-16 |
| ATE91583T1 (en) | 1993-07-15 |
| EP0269094A2 (en) | 1988-06-01 |
| EP0269094B1 (en) | 1993-07-14 |
| EP0269094A3 (en) | 1990-04-04 |
| US4755871A (en) | 1988-07-05 |
| DE3786529D1 (en) | 1993-08-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 19980928 |