Note: Descriptions are shown in the official language in which they were submitted.
3~
~ 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 .
~1~
_ I _
pc/ ,~
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/
~3~
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/
3~
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/
3~
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
-- 3 --
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-
3~
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.
--'I ()--
