CA1183901A - Radio link remote control signaling system, and method - Google Patents

Abstract

A B S T R A C T

To permit simultaneous transmission of command codes, in binary command words, with traffic or other announcements, being broadcast over an FM transmitter which has a 57 kHz subcarrier AM modulated by an announcement recognition (AR) signal, for example 125 Hz, use is made of the long response time of AR switching elements to provide, before the AR
switching element (13) can respond, decoding of a command word at a clock rate which is fast with respect to the response time of the long switching time constant switching element (13). This fast response is, preferably, accomplished by a counter (18) which has only the number of count positions corresponding to the bits in the command word, then provides an overflow to block a memory (15) in which the bits are being stored; a second counter(20)--or a continuing portion of the counter--counting at the clock rate for a period of time longer than the response time of the switching element (13) to then cause unblocking of the memory, for subsequent reception of command words, which may occur during transmission of the AR signal, by merely short interruptions thereof, insufficiently long to prevent drop-out of the switching element (13) of the AR system. A decoder (30) is connected to decode the expected command words, but reject AR signals, the characteristics of both of which are known.

Description

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~ rhe present invention rela-tes to a remote control system and more particularly to a remote control system which a radio link and which is so arranged that specific informa-tion transmîtted in binary form over a subcarrier on a radio communica-tion channel can be readily decoded, and separated from other information being transmitted over a radio tr~nsmission channel.
Background. A referenced publication "Rundfunktechnische Mitteilungen" (information on radio technology) Vol. 12 (196~), issue 5, pp 214/216 describes remote control systems for use in combination with radio stations in which an ultra high frequency (UHF) transmitter, for example operating within the frequency modulation (FM) commercial band has modulated thereon a frequency of 50 kHz in addition to the radio program. The subcarrier of 50 kHz has low modulation, and is continuously modulated on the normal carrier frequency of the transmitterO This additional frequency is used to synchronize quartz oscillator generators of medium wave transmitters.
The frequency of 5Q kHz, forming a normalizing frequency, can be interrupted, that is, this subcarrier can be used to transmit remote control commands by interrupting the subcarrier in form of a binary pulse sequence with a repetition of operating frequency of 100 BAUD. The pulse sequence is used to transmit remote control commands to control rapidly responding transfer switches in a transmitter stationO This Erequency~ Eor ~xample~
may be used to transmit such remote control commands from a studio to a remote transmitter~ or from one remote transmitter to arlo ther .
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Television converters which have slowly responding transfer switches, and which may be associated with the transmitters can be switched by providing another subcarrier, for example of 37.5 kHz, transrnitted by the UHF transmitters.
The 37.5 k~z subcarrier is radiated only if a command, in form of a pulse sequence must be transmitted. The transmission of such a command may have a duration of up to about 10 seconds.
rhe Invention. It is an object of the present invention to reduce the system and apparatus requirements to lQ control, respectively, rapidly responding and slowing responding transfer switches, and to utilize only a single subcarrier which can control, selectively, the rapidly and slowly responding switches so that remote control commands can be radiated from a radio station on which only a single subcarrier is modulated.
According to one aspect of the present invention there is provided a remote control sys-tem having a radio transmission link on which a signal including program information and binary control information is being transmitted between a transmitting station and a receiving station on an ultra-high frequency carrier. The program information is frequency modulated (F~) on the carrier, and provided an auxiliary carrier (57 kHz) which is frequency modulated on the ultra-high frequency carrier. A first control modulating signal (AR) which is amplitude modulated (AM) on the auxiliary carrier, is adapted for effecting receiver switching with long switching response time characteristics. A second control modulating signal, which is ~M modulated on the auxiliary carrier in the form of a predetermined nurnber of bits, forms command words which have a repetition rate such that the cornmand words are short with respect to the switching response of the long switching response time characteristic, the receiving station cornprising a detector for detecting the auxiliary carrier, a demodulator coupled -to the detector for providing the first and second control modulating signals, a data receiver being connected to the demodulator to receive the first and the second con-trol modulating signals, and having me~ns for responding only to the second of the control sb/

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modulating siynals. The last mentioned means includes a memory having a capacity for receiving only the predetermined number of bits forming the command words, and a clock controllirlg storage of the bits in the memory, the clock having a repetition rate which is capable of controlling storage of the number of bits in the memory during a time less than the switching time, and means for blocking storage of information in the memory fox a period of time which exceeds the switching response time.
According to another aspect of the present invention there is provided a method of remotely controlling and providing a control output utilizing a radio link on which control information and other information is being transmitted.
The method includes the steps of providing a UHF carrier, frequency modulating the UHF carrier with audio information and frequency modulating an auxiliary subcarrier (57 kHz) on the carrier. The auxiliary subcarrier ls amplitude modulated wth a first control modulating signal (AR) to effect switching in a receiver of a switching stage which has a long switching response time characteristic. The auxiliary subcarrier is amplitude modulated with a second control modulating signal in the form of predetermined number of binary signals forming command words which have a repetition rate and transmission time which are short with respect to the switching response time. All of the modulating signals are transmitted on UHF carrier, and the so modulated and transmitted signals are received. The method further includes the steps of providing a clock time base and storing received signals in a memory having only the capacity of the number of bits in the command words, under control of the clock, and blocking storage of further signals applied to the memory subsequent to filling of the memory by the binary signals of the command words to thereby distinguish between command words having a time duration which are short with respect to the long switching response time, and decoding the signals stored in the memory wi-th respec-t to predetermined command word codes to (a) store and decode only command words, and (b) provide for response - 2a -sb/

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to the first control modulating signal only when the first control modulating signal persists for the duratlon of the long switching respo~se time.
It may be seen, therefore, that in the present invention, a data receiver may be connected to receive first and second control modulations which, respectively, control slowly and rapidly responding switching devices. The da-ta receiver is arranged to respond, respectively, to -the respective control modulations and, in accordance with a feature of the invention, differentiation is done this way: a memory is provided having a capacity of receiving only a predetermined number of binary signals. A clock controls storage of the binary signals in the memory. The clock has a repetition rate which is capable of controlling storage of that number of binary signals in the memory for which it is designed during a period of time which is less than the switching response time of the slowly responding switching element. The memory is blocked for a period of time which exceeds this switching response time. The switching response time, that is, the change of state of the slowly responding switching response element, 2b -sb/

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preferably, is the same for switching from a fi.rst to a second mode, and back from a second to a first mode.
In accordance with a feature of the invention, the memory includes a counter which, when the count num~er corresponding to the predetermined number of binary signals is exceeded provides an overflow signal which blocks further storage of data in the memory and enables a second counter to count out the remainder of the time required for the switching response time of the slowly opera-ting switching devices~
The system of the present invention is particularly adapted for combination with transmission systems in which switching eommands are transmitted on a subcarrier, for example to eharacterize particular types of transmission. Details of such partieular types of transmissions are explained in U.S.
patent 3,949,~01, Hegler et al, issued April ~, 1976 whieh deseribes a transmission and r~eeption, that is, a radio informat:ion system in which radio stations broadcast programs which, however, can be interrupted by special announeements, for example traffic or emergency announcemen-ts. To be sure that a user or operator of the radio :is tuned to a station whieh does provide such special announcements, the radio station, or various radio st.ations within a region radiate, in addition to the program, or information signal, a 57 kHz subcarrier on which, depending on the radio station or reg.ion, a particular radio station or recJ.ion recognition frequency or signal, hereinafter RR s.icJna~. is moclulated. The receiver operator, thus, can tune~-manual:L~ or automat.i.ccll:Ly--to radio stations which, in addition to thei.r program, radiate the particular RR frec~uency. At the time wh~ll an announeement is beincJ broaclcast, the subcarrier is pc/, ~

modulated by a special announcemen-t recognit:ion, hereinafter AR, fre~uency which can be de-tected in the receiver and used to efEect switching func-tion thereinr for example by cancelling a muting switch which previously silenced reproduction of the program from the transmitter; or by changing-over reproduction of progra.m content taken Erom a magnetic tape, or other stored transducer, to enable the operator or user to hear the special announcement. Details of such systems are also disclosed in Eilers and Bragas Canadian applications Serial Nos. 399,917, filed March 31, 1982; 399,947t filed March 31, 1982; and 399,9~8, issued March 31, 1982.
In accordance with a feature of the invention, additional switching commands can be transmitted -to receivers which are designed for reception of these commands without an additional subcarrier. The receivers need not, necessarily, have a reproduction portion which also reproduces the special announcements, that is, which respond to the AR signals. The receivers, however, must be able to distinguish between the remote control commands and the AR signals. In accordance with a -Eeature of the present invention, the remote control system permits transmission of information additional to the special announcements, that is, the AR signal. The already present decoding system permits transmission of additional inEormation/
since the presently used system is completely compatable with FM
programming and radiation thereof.
In accordance with a feature of the invention, a 125 Hz modulcation on the subcarr:ier:is rad:iated not on.ly to characterize an anrlc)~mcement--~hat i.s, to:Eo.rm the ~R s:i.~nal--and to thereby control sw.itch:in~
w:i.th:i.n the rcce:iver desicJned there:Eore, but, addit.ionally, to itself form a pc/~

remote con-trol command signal which, in binary form, permits transmission of remote control commands for those receivers which are capable of decoding E~C//~ 5 -these commands, arld, of course, can distinguish between the commands which are radiated in blnary form and the switching commands characterized in an annollncement.
The receivers which are capable o~ receiving the special announcements, particularly for use in automobile radios and especially in combined automobile radio/cassette recorders utilize transfer switches which have a :Long response time constant. In accordance with a feature of the invention, the long response time constant of the customarily used switch-over elements is used to descrimlnate between rapidly transmitted remote control commands before the long response time switching elements can respond.
As in all remote control systems, and particularly in those which utilize a single transmission channel, assurance against malfunct~on or er~neous response must be provided.
The auxiliary AM modulation of 125 Hz is modulated on the 57 KhZ subcarrier in form of amplitude modulation, the 57 kHz subcarrier additlonally being modulated by further amplitude modulation tAM) frequencies which are used for recognition of the radio station or region--the RR signal. Continuous transmission of a third modulation on the 57 k~lz subcarrier, wlth a further third AM modulating frequency is, therefore, excluded for all practical purpo~es. Reliability of unambiguous decoding of remote control commands with respect to AR signals can be obtained, however, by utilizing a counter in the decoding clrcuit which is so matched to the bits of the command that the counter provides an over~Low out~ut wcll in advance of the response time of the switcllil)g elements which are to respond to the AR, or the KR signal.
In accordance with the prLor art--see, for example, the referenced "Rundfunktccllni-icl)c M:itteillJngen" literature, ~he 50 kHz normalizing frequency can be used to efEect control of switching of a rapidly operat:ing swi.tch in a transmitter and, further, synchronization of an vscilator. For synchronization~
short-time interruption of radiation of the auxiliary carrier does not matter, since the oscilator will continue to operate, at its quartz control frequency, for some ti.me without drift.
Short sequential pulses of the 50 kllz frequency, that is, the normalizing frequency which form the bits o:E a command word also do not interfer with synchronization, since the 50 k~lz auxiliary carrier only provicles a reference value which is readily available for sufficient time in the form of a pulses following the pulse gaps of the binary words which comprise the remote control command word.
lS In thc systems of the referellced Hegler Patent 3,949,401, and as explair.ed in cdetail in tlle referenced ~ilers and Bragas applications, the AR frequency or signal of 125 Hz is modulated on the subcarrier only when an announcement :Ls actually being given.
Drawln~
~ig. 1 is a general bloclc diagram of a receiver capable of responding both to announcement recognition signa:Ls and to remote control command words;
Fig. 2 is a detailed circuit cliagram of the command word data receiver portion;
Fig. 3 is a fragmentary cliagram of the command word decoding port:Lon lllustrating a moclif:lcat:ion;
Fig. 4 is another fragnmelltary cl:ingram illustrating anotlier modificaitiorl.

Detailed Decri~_ion. rI`I~e anL~nna 1 of a radio receiver receives trarsmitted sign<lls, for examI)Ie within the commercial UHF-FM band, and conducts signals to a R~ tuIler and input stage

2. The tuner 2 can be tuned nnanually, or automatically, for example it may have a signal search circuit, for tuning to a desired transmitter. The tuner 2 is connected to an intermediate frequency (IY) stage 3, whicl- provides its output signal to a detector 4, a ratio detector, from which program audio infor-mat~on in the form of audio signals can be received, amplified L0 in audio amplifier 5 for reproduction in the loud speaker 6.
Other circuits, for exampLe noise Eiltering, limit a circuit limiter and the like have been omitted from the diagram for clarity and can be used, as well known.
Some of the receivers which can be tuned by the tuner 2, in addition to the program content modulated on the carrier by FM modulation~also radiate a 57 kllz subcarrier, which is provided to transmit switching commands from the transmitter to the receiver, or to provlde information regarding the capability of the particular transmitter to provide specific announcements, or to characterize a specific geographic location of the transmitter.
The auxiliary 57 k~lz subcarrier, which is modulated both by eommands and information was uti1ized to characterize those transmitters wlILch, more or less regularly, provide special announeements, for example traffic, or emergency announcements, news, sports announcelllents or tl1e like. I)uril1g such an announcement, the 57 k~Iz suI-carr k!r has a 125 llz A~l modulation applied thereto. The cle~,ree o~ moclulation may cl-lange, for exampLe be in the order of aholIt 3()'~; the reEererIced l~ilers and Bragas appLlcatLon.s deL;C r il)e V.lr ;I)IIS n~O(IU lat jOn r)OSS1hi] LtieS.

The amplitude of the 57 k~lz subcarrier is also continuously modulated with the regLon, or r~l~Lo station recognLtion signa] (RR).
The frequency of the additional RR signal will depend on the geographical location, or the particular characteristics of the transmitter. The RR frequency may vary between about 20 Hz to ~ust under 125 Hz. The degree of modulation by the RR signal, at least during absence of the AR signal may be higher, for example about 60%. Various changes in modulation degree may be made, and reference is made to the referenced applications ~or detalls of the systems and appropriate modulations.
The standard radio receiver, for example an FM automobile rece-Lver which has the elements 1-6, if adapted to also receive special announcements radiated by specially adapted or authorized and characterized transmitters,includes a 57 kHz detectar 7 which i5 connected to the output of the ratio detector 4. The 57 kHæ detector 7, which detects a 57 kllz FM modulation on the original signal received by the antenna I i~ connected to an auxiliary carrier output indicator 8 which indicates the presence of the auxilary 57 kHz subcarrier, that is, that the particular transmitter does radiate thi.s sul)carrier. The indicator 8 may, additiollally, be used for switching. In addition, the 57 kHz detector 7 provides an output to an AM demodulator 9 to demodulate the amplitude modulation applied to the 57 kHz subcarrier. The output signal from demodulator 9 is applied to two filters lO and 12, whicll are respectiveLy arranged and designed to select diEferent Erequen(:y bands. Iilter lO is a low pass filter which selects those fre~uencies which are wlthln the frequency range of the RR si.gna:1, that :i~i, below 125 Hz, for cxamplc betwcc11 2() to 6() 11~. 'I'he f1lter lO :Ls connected to a stage ll, whLcl1 form6 a reg:Lon or radio station recognition Lndicator ll. In~licator ll, aclditionally, may be used to provide switching signals~ may have selector switches connected thereto so that the user can select a specific region, or radio station or the like. I'he second fllter 12 is a band pass filter WhiCll Eiltcrs the L25 llz modulation for the AR switching network 13. The ~R swltching network is provided in those receivers which can reproduce special announcements, that is, which will reproduce the program content amplified by audio amplifier 5 and the loudspeaker 6 during the presences of the AR, that is, 125 Hz signal. Circuit 13 carl, additionally, be used to enable reproduction from loudspeaker 6 iE the loud-speaker, previously, has been muted, or, for instance, to transfer reproduction from a recorded, e.g. tape recorded program to the special announcement.
In accordance with standard procedure, the 'ransfer switch 13 has a long response time constant. This response time constant, of course, i5 short with respect to the duration of even the shortest announcement which would be radiated by the transmitter, for reproduction tl-rougl-l lou(lspe.lkcr 6.
In accordance wLth a fcature of the present ~nvention, a spec:lal data decoder, or data receiver 14 is connected in parallel with the switchirlg network 13. The output terminal 12a from the 125 Hz band pass filter 12 thus is connected to both the stages 13 and 14.
Data receiver and decoder 14--see Fig. 2--is provided to decode the command words, in form of pulse bits, or binary pulse slgnals which utilizes the 12'~ llz osci]lation. The respective puIses preferabLy shoul-l have a duration of 10 to 15 periods or undulations of tlle ]25 llz Erequellcy. A pulse command word oE 16 b-Lts thus wll 1. I~llVC a duratlorl oE about . I ( ) _ ~3~

a second. Such a pulse comllland word can rcadily be decoded by the decoding or data receiver 14 wiLhout interfering with proper switching f~lnctions of ~he AR switch L3 The data receiver or decoder 14, in accordance with a feature of the invention, includes a memory 15 having an in-put circuit 16. The incoming signals, coupled from terminal 12a are connected through the input circuit 16 to ~ memory 15, and, additionally, to a counter input stage 19 of a first counter 18. Stage 14 further includes a clock generator 17. The clock pulses are counted in th~ first counter L8 as soon as the first pulse of a command word is sensed by the counter input 19, thus opening the input to the counter 18 and causing the counter to count. The counter 18 has the number of bit positions which correspond to tile bit number of a data word. The clock pulses, in accordance wlth well known technology, control reading-in of the bits of the pulse command word into the memory 15~ as well as evaluation of the stored data, in a decoder 30, the output of which is transmitted to an output terminal 30a. The clock 17 has a clock output terminal L7a wl-ich, as well known, controls the memory l5 as wcll as Lhc dccodcr 30.
The fLrst counter 18 has an overflow line 18a which Ls connected to a control input terminal of the input stage 1~ for the memory 15. If an overflow pulse is derived from counter 18, the input stage 16 will block. Subsequent count pulses, however, are counted in the second counter 20 The overflow terminal from the counter 20 is connected to a line 20a which is connected to the input terminal 16 to unblock, or release the input stage 16 The freq-lency, or repetit-Lon rat(! of the clock l7 is so selected that the duratLon o~ thc cntlre plllse word, that is, -- I L --~3~

the storage time wi.thin the memory l5, or the counting time within the counter 18 before an overflow pu.lse occurs, i9 less the response time constant of the AR switch 13. The number of count positions of the second counter is so selected that, upon subsequent counting beyond overflow of the counter 18, the time for the second overflow pu].se on ]ine 20a is above the response time constallt Or the transEer switching stage 13 Operation: The transfer switching stage 13 will not respond, either upon transmission of a single remote control command word, or upon transmission of several subsequent remote control command words, since the duration of any one remote control command word ls less than the response time of the transfer switchi.ng circuit 13 which, as noted, may for e~ample lS disable a muting circuit as soon as an AR signal is being radiated. In accordance with a feature of the invention, sequential command words are separated by a pause which is longer than the response time period of the switching network 13, so that even subsequent command words cannot be decoded, erroneously, as an AR signal. The change-over of switching from one state to another, and back from the other state to th~ first of the transfer switch 13 should be about the same.
This insures that a command word which is superimposed on radiation of an announcement recognition, AR signal, does not trigger the return of the switching stage 13 to its first state, or, in other words, does not cause switching stage 13 to erroneously consider that the announcemcnt has been terminated, and thus changes over to the E)revious state during which ~he AR signal normally would be absent . Tl~us 9 it i.s poss:Lble to radlate the AR signal, witll rnpi(l :interrupt:Lol-s to form a -:l.2-

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command word which, however, overall are substantially shorter than the response ti~lle of the switch 13, regardless oE the switching state thereof. If the return switching time is shorter, then command words cannot be radiated during presence of the AR slgnal.
If a command word follows immediately upon termination of a AR signal, the AR switclling state 13 will retain its switched st,3te. Slnce, howevcr, no further announcernent is being radlated, merely keeping the AR switch in switched state for the extremely short period of another command word will not interfer~with operation of the system or interferewith listening by a user.
The system requires at the transmitter an arrangemPnt which provides for a similar clock fre~uency as clock 17, which controls radiation of the command word, and maintenance of the same pauses or pause duration between successive remote control ommand words. Additionally, the transmitter shouLd be so arranged that it, seLectively, can radiate the 125 Hz si~nal to lndicate an announcement, or to transmit remote control co~nmand words. Furtller, the transmitter should be so interlocked that if a command word is to be transm-itted during an announce-ment, that ls, when che ~R signai is modll]ated on the 57 KhZ
subcarrier, the clata word for remotc control cnmmand is transmitted only after the overall time for counting by the two counters 18 and 20 has elapsed, that is, that first the response time of the switch 13 is considered before a command word is transmltted. I'referabLy, the totaL time for counting by both counters 18, 20 is somewhat longer than the response tlme of the switch 13, to accommoclnte tolerances alld varlations ln response tlme of varLous swit~ es L3 Ln var-ious receivers.

The countlng time of the two counters 18, 20, thus forms a eonvenient overal.l time before a remote control. command work ean be transmitted d.lr:ing transmission of an AR signal.
Preferably, a multiple of this time of both counters 1$, 20, should be used. This is desirab].e since, as looked at from the reeeiver, the duration of the radiation of the 125 Hz AM
modulation will be considered as tl-e heginn:ing of a command word whieh, however, will not be decoded in form of a eommand since lt will persist after t'he overflow l.ine 18a has responded.
Of eourse, the decoder 30 ean readily be arranged to distingulsh between a command word and an AR recognition signal in accordanee with well-known deeoding technology.
Fig. 3 illustrates another embodiment. Both eireuits are identieal up to the output of the AM demodulator 9. ~he lS band pass, however, should have a sl.ightly different pass eharaeteristic. Thus, band pass filter 12 should be capable of separating 125 Hz as well as l37.5 Hz from the RR signals.
the In aeeordance with / feature of the invention of Fig. 3, two parallel eontrol frequency Filters 21, 22 are conneeted to the output from band pass filter 12'. The eontrol frequeney filter 21, whieh has a eharacteristic pass frequency of 125 Hæ
is eonneeted to the AR transfer switch 13. The filter 22 is connected to the data recelver 1~ via terminal 12a. 'In aeeordanee with the system of Fig. 3, the command frequeney i9 radiated by modulating the 57 kllz subearrier by a frequeney different from the AR frequeney, for example 137.5 llz. In aeeordance with this .system, the ~R frequeney i~s interrupted durlng. transmlsslon of a comllland wo~cl. The duratloll of the eommand word, and the pnuses between two subsequent eommand word~ clo not lnterEer w:Lth tlle sw:itchlng t:ime oE the long response time sw:Lteh.ing e:l.emellt l3, clnd w:il.l not :influenee the response thereof.

-.I.4-Interruption oE the radiation of the AR frequency at the transmitter is necessary since only one further frequency can be modulated on the 57 kilz suhcarrier besides the RR
frequency, selected by the Eilter lq. Thus, in the embodiment of Fig. 3, the 57 kllz subcarrier is seLectively AM moclulated with the command word at 137.5 Hz or the AR Frequency at 125 E~z.
Actua] experiments have shown that, apparently, the embodi~ent of Fig. 3 has a higher clegree of ambiguity rejection than that discussed in connection with Figs. l and 2.
lOEmbodiment of Fig. 4: TS~e band pass filter 12'' which has an even wider band pass than filter 12' is connected to three frequency filters ~1, 22, 23. Filter 21, again, selects the 125 Hz AM modulation to control the transfer switch 13.
Fllter 22 selects 137.5 llz to control the data receiver 14' .
15Filter 23 is set to select a frequency of 175 }Iz, the ontput of which, for example via decoul)ling network 24, is connected to the data receiver l4' .
Operation: If no anno-lncement frecluency 125 Hz, that is, the AR signal is being radiated, a commar-LI data word can be 2U radiated by frequency shift tccl~noLogy, in which, rather than providing pulses ar-d pulse gaps, the frequency of the modulation is shifted between 137.5 llz and L75 llz, clepending upon whether a binary-one or a binary-zcro is to be transmitted. The data receiver 14' , then, will respond to rreqllcncy shift, rather than to pu]ses and absenccc; of pulses. ~reclllency shiEt technology, and decoding thLreof is well known. The variation thus descrlbecl can a]so be utilized in the system of Fig. 3, as lndicated by the brokcn line ~la, connectecl from the 125 llz filter 21 to the clLIta receiver 14, which, then, should be of tl-~ freqnency-silift responsc typc, simLI.Ir to clata ~3~
receiver 14' . Utili~ing this variation, frequency-sllift is carried out between 125 and 137.5 llz~ that is, utili~ing the AR frequency with very short response time collstant. This variation is particularly suitable iE, from a transmitter, the command data word is transmitted by way of frequency-shift between the 125 H~ and the 137.5 Hz frcquencies.
It is not necessary that the data receiver 14 forms part of an overall automotive-type announcement receiver which includes the switching network 13; iE the receiver is arranged only to decode command words, for e~ample to control transmitter functions, or to effect other remote control functions, the portion of the receiver including stages 5, 6 and 13 can be omitted. Yet, since the transmitter will transmit both the AR signals, to be received in receivers designed for their reception, as well as the command words, unambiguous decoding, respectively, of the AR signals, and the remote control command data words is necessary, which is effect by the decoding circuits 14, 14', respectively.
Various changes and modifications may be made within the scope of the inventive concept.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Remote control system having a radio transmission link on which a signal comprising program information and binary control information is being transmitted between a transmitting station and a receiving station on an ultra-high frequency carrier, said program information being frequency modulated (FM) on the carrier, an auxiliary carrier (57 kHz) which is frequency modulated on said ultra-high frequency carrier, a first control modulating signal (AR) which is am-plitude modulated (AM) on the auxiliary carrier, and adapted for effecting receiver switching with long switching response time characteristics, a second control modulating signal which is AM mod-ulated on the auxiliary carrier in the form of a predetermined number of bits, forming command words, which have a repetition rate such that the command words are short with respect to said switching response time of said long switching response time characteristic, said receiving station comprising a detector for detecting said auxiliary carrier, demodulator coupled to detector for providing first and second control modulating signals, a data receiver (14) connected to said demodulator to receive the first and second control modulating signals, and having means for responding only to the second of the control modulating signals comprising a memory (15) having a capacity of receiving only said predetermined number of bits forming said command words;
and a clock (17) controlling storage of said bits in the memory, said clock having a repetition rate which is capable of controlling storage of said number of bits in the memory during a time less than said switching time, and means (18a) for blocking storage of information in said memory for a period of time which exceed said switching response time.

2. System according to claim 1 wherein the switch-ing response time of switching from a first to a second state and from a second state to a first state is equal.

3. System according to claim 2 wherein the gap between sequential command words is longer than said switch-ing response time.

4. System according to claim 1 wherein said data receiver (14) comprises two sequentially connected counters (18, 20), and said means for blocking the memory (15) comprises an overflow connection (18a) from the first counter to the memory to block storage of bits in the memory when the first counter has an overflow;
and wherein the second counter (20) has a count number which, at the clock frequency, or clock repetition rate of said clock provides an overflow output occurring after said response time has elapsed, said overflow output from the second counter being connected to unblock the memory.

5. System according to claim 1 including two filters (21, 22; 22, 23, 24) connected to the input of the data receiver and, respectively, being tuned to different frequencies to provide for discrimination between the first and second control modulating signals.

6. System according to claim 5 wherein the command words are transmitted in form of frequency-shift signals.

7. System according to claim 6 wherein the frequency-shift of said command words is between the frequency of said first control modulating signals and a different frequency characteristic of the second control modulating signals.

8. System according to claim 6 wherein the frequency-shift is between two frequencies differing from said first control modulating signal.

9. System according to claim 6 wherein, during transmission of the first control modulation, the second control modulation is absent; and, conversely, during trans-mission of the second control modulation, the first control modulation is absent.

10. Method of remotely controlling and providing a control output (30a) utilizing a radio link on which control information and other information is being transmitted compris-ing the steps of providing a UHF carrier;
frequency modulating said UHF carrier with audio information;

frequency modulating an auxiliary subcarrier (57 kHz) on said carrier;
amplitude modulating said auxiliary subcarrier with a first control modulating signal (AR) to effect switching in a receiver of a switching stage (13) which has a long switching response time characteristic;
amplitude modulating the auxiliary subcarrier with a second control modulating signal in the form of a predeter-mined number of binary signals forming command words which have a repetition rate and transmission time which are short with respect to said switching response time;
transmitting all the modulated signals on said UHF carrier;
receiving said so modulated and transmitted signals;
providing a clock time base (17);
storing received signals in a memory having only the capacity of the number of bits in said command words, under control of said clock, and blocking storage of further signals applied to said memory subsequent to filling of the memory by the binary signals of said command words to thereby distinguish between command words having a time duration which are short with respect to said long switching response time, and decoding the signals stored in the memory with respect to predetermined command word codes to (a) store and decode only command words, and (b) provide for response to said first control modulating signal only when said first control modulating signals persists for the duration of said long switching response time.

11. Method according to claim 10 including the step of counting binary signals, and storing binary signals in the memory only if the count number matches a predetermined count;
and continuing counting at the rate of said clock for a period of time at least as long as said long switching response time, and then unblocking the memory, to permit re-sponse to the first control modulating signal by apparatus having said long switching response time without spurious response due to ambiguity within a command word.

12. Method according to claim 10 including the step of changing the frequency between said first control modulating signal with respect to said second control modulat-ing signal, and transmitting, selectively, only the one, or the other of said control modulations.

13. Method according to claim 12 wherein the command words are transmitted by frequency-shift characterization of respective values of the bits of the command words.