Receiver having a light emitting display as frequency and tuning indicator

A receiver having a light emitting display device indicating the frequency to which the receiver is tuned and the presence or absence of a received signal by the use of visually distinct display modes. In one embodiment, a first color indicates no received signal and a second color display indicates the presence of a received signal. In another embodiment, a first color indicates no received signal, a second color indicates approximate tuning and a third color indicates exact tuning of a received signal.

BACKGROUND OF THE INVENTION 
The present invention relates to a receiver comprising a frequency display 
device. 
Amplitude modulation (AM) and/or frequency modulation (FM) receivers are in 
general equipped with a frequency display device formed of a frequency 
graduated dial and a needle integral with the system for tuning in the 
station (variable capacitor, variable inductance, voltage control of a 
Varicap diode). In the case of station tuning using one or more Varicap 
diodes, it is advantageous to use a frequency and wavelength graduated 
dial associated with a frequency device of the electronic light needle 
type which is generally an array of light-emitting diodes, associated with 
a control circuit. A single diode is lit up, controlled by a threshold 
element indicating the frequency on the dial, after calibration. 
Whatever the mode of reference marking used, it is important to set the 
receiver exactly to the frequency of the transmitter. For that, use must 
be made of a tuning indicator. This may be a simple galvanometer with 
middle point or a more or less sophisticated electronic system. 
These known systems have the drawback that the user is forced to look 
alternately at the tuning indicator and at the dial of the apparatus where 
the frequency indication is given. 
The present invention has as its object a receiver free of the above 
drawback. 
SUMMARY OF THE INVENTION 
The invention thus provides a receiver comprising a receiving circuit, a 
tuning detector and a frequency display device, wherein the tuning 
detector is associated with the frequency display device so that the 
frequency display appears in a first mode in the absence of a signal from 
the tuning detector and representing tuning in to a station and in a 
second mode visually distinct from the first one in the presence of such a 
signal. 
According to one embodiment of the invention, in the presence of a signal 
representing tuning to a station, said tuning detector is associated with 
the frequency display device so that the display appears on the dial 
according to the second mode in the presence of a signal associated with 
an exact or presumed exact tuning and according to a third mode visually 
distinct from the first two in the presence of a signal associated with an 
approximate tuning. 
The frequency display device may comprise a display control circuit and a 
frequency light display device. 
According to a preferred embodiment, said indication modes consist of 
distinct colors. 
Thus, the frequency light display device may consist of a light needles 
comprising a plurality of display elements each of which is capable of 
causing an indication to appear in at least two distinct colors and be 
associated with a light needle control circuit receiving from the 
receiving circuit of the receiver a control voltage representative of the 
frequency to which the receiver is tuned and producing accordingly at one 
of its n outputs a signal representative of said frequency, the tuning 
detector receiving from said receiving circuit a signal representing the 
field received and/or at least one signal from a discriminator of said 
receiving circuit. Each display element may be formed for example from two 
or even three light emitting components, for example diodes. 
Further, for amplitude modulation transmission, the tuning detector 
receives from the receiving circuit the amplitude modulation field and/or 
the zero and the S curve of an amplitude modulation discriminator. 
For frequency modulation transmission, the tuning detector receives from 
the receiving circuit at least the zero of the discriminator and possibly 
the S curve of this latter and/or the frequency modulation field.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a frequency light display device 11 of the light needle type 
comprising a number of light-emitting components(IL.sub.1, IL.sub.2 ; . . 
. ,IL.sub.p, . . . IL.sub.n). Such a light needle may be formed from an 
array of light-emitting diodes. The light needle is associated with 
graduations corresponding respectively to the frequency modulation band FM 
and to one or more amplitude modulation bands (long waves, medium waves 
etc.). The light indication is obtained by lighting a single one of the 
components, e.g. component IL.sub.p, p being variable from 1 to n. 
For such a display, the receiver comprises conventionally a receiving 
circuit as well as a display control circuit. A conventional receiver also 
comprises in general a tuning detector which provides a tuning display, 
independently of the frequency display. 
FIG. 2 shows a receiver in accordance with the invention comprising a 
receiving circuit 10 which supplies, in a way known per se, one or more 
signals to a tuning detector 30, as well as a control voltage to a light 
needle control circuit 20. The frequency light display device 11 is of the 
light needle type, where each light-emitting element (IL.sub.1, IL.sub.2, 
. . . ,IL.sub.p, . . . IL.sub.n), comprises two light-emitting components, 
for example diodes DR.sub.1 and DV.sub.1, DR.sub.2 and DV.sub.2, DR.sub.3 
and DV.sub.3 . . . , DR.sub.p and DV.sub.p, . . . DR.sub.n and DV.sub.n. 
For example, diodes DR.sub.p, with p varying from 1 to n, emit in the red 
and diodes DV.sub.p, with p varying from 1 to n, emit in the green. A 
logic circuit 40 receives signals from the tuning detector 30 and from the 
light needle control circuit 20, and is associated with the frequency 
light display device 11, in this case of the light needle type, so that 
the frequency light indication appears on the frequency light display 
device 11 according to a first mode in absence of a signal from tuning 
detector 30 and representing tuning in to a station, and according to at 
least a second mode visually distinct from the first one in the presence 
of such a signal. The purpose of logic circuit 40 is then generally to 
appropriately interconnect the display device, the circuit driving the 
display, for example of the light needle type, and the tuning detector. 
Thus, with the red and green diodes mentioned above, frequency light 
indication may appear in red if there is no station tuning and in green if 
there is tuning. 
The embodiment of FIG. 2 will now be described in greater detail. The 
cathodes of all the light-emitting diodes are connected to ground. In 
fact, the two-diode light-emitting elements are generally in the form of 
cases in which the cathodes of the two diodes are common. The logic 
circuit 40 will process in parallel the information supplied by the light 
needle control circuit 20 and by the tuning detector 30. Let us thus 
consider any light-emitting element IL.sub.p, p varying from 1 to n. The 
anode of its first diode DR.sub.p, which forms its free electrode, is 
connected to the output of an AND gate PR.sub.p. The anode of its second 
diode DV.sub.p, which forms its free electrode, is connected to the output 
of an AND gate PV.sub.p. A first input of AND gate PR.sub.p as well as a 
first input of AND gate PV.sub.p receive the output S.sub.p, of rank p, 
from the light needle control circuit 20 in accordance with positive 
logic, that is to say that this signal S.sub.p is at logic level 1 and 
all the others at logic level 0 when the reception frequency selected 
corresponds to illumination of element IL.sub.p of the light needle. For 
example, the light needle control circuit UAA 170 from SIEMENS supplies 
directly output signals in accordance with a positive logic. On the other 
hand, the tuning detector which, for example, in frequency modulation, 
receives the zero of the discriminator of the receiving circuit 10, 
produces at its output a signal A corresponding to tuning in to a station, 
with negative logic, i.e. that when tuned in to a station, this output A 
is at logic level 0. The tuning detector LB 1450 of SANYO may for example 
be used. Signal Ais applied to an inverter I.sub.1 whose output is a 
signal A representing then station tuning with positive logic. Signal A is 
applied to the second input of AND gate PR.sub.p as well of course to all 
the other analog gates namely PR.sub.1, PR.sub.2, PR.sub.3, . . . , 
PR.sub.p, . . . , PR.sub.n. Similarly, signal A is applied to the second 
input of each of the gates PV.sub.1, PV.sub.2, PV.sub.3, . . . , PV.sub.p, 
. . . PV.sub.n . Therefore, if a level 1 logic signal is supplied by 
output S.sub.p, p varying from 1 to n, it is diode DR.sub.p which will 
light up in the absence of station tuning and diode DV.sub.p which will 
light up in the presence of station tuning. Diodes PR.sub.p and PV.sub.p, 
whatever p'.noteq.p) will not light up since S.sub.p',=0. With the above 
example, the user will see a light element IL.sub.p red in color if there 
is no station tuning and green in color if there is station tuning. 
It will be noted that light-emitting components other than diodes may be 
used. If their common electrodes are connected to ground, they will be 
named cathodes and anodes if they are connected to a supply voltage. 
FIG. 3 is a variation of FIG. 2, using for example diodes whose anodes are 
connected to a case forming the light-emitting element IL.sub.p. For the 
sake of simplicity, this figure in fact only shows the light element or 
rank p, the situation being of course identical for all the other 
light-emitting elements. The AND gates PR.sub.p and PV.sub.p are simply 
replaced respectively by inverting AND gates P'R.sub.p and P'V.sub.p, 
which furthermore receive the same signals as in the case of FIG. 2. 
FIG. 4 shows a more elaborate version of FIGS. 2 and 3 for obtaining not 2 
but 3 display modes for the frequency light indication. For example, for 
light-emitting elements comprising a red diode and a green diode, the 
indication will be red in the absence of tuning, orange for approximate 
tuning by causing both diodes to emit simultaneously, and green in the 
presence of exact station tuning. For this, the tuning detector 30 
receives from the receiving circuit 10, not only the zero from the FM 
discriminator but also the S curve thereof so as to be able to output, in 
a way known per se, signals PA.sub.1 and PA.sub.2 representing an 
approximate station tuning. For example, the circuit mentioned above by 
way of example supplies such signals with negative logic, i.e. approximate 
tuning in to a station produces a logic level 0 at one of the two outputs 
PA.sub.1 and PA.sub.2. In the total absence of tuning or in the case of 
exact tuning to a station, these two outputs are at level 1. Signal 
PA.sub.1 is applied to an inverter I.sub.2 which outputs an approximate 
tuning signal PA.sub.1 with positive logic. Signal A is applied to the 
input of an inverter I.sub.3 which outputs a station tuning signal A with 
positive logic, as did the inverter I.sub.1 of FIG. 1. The signal PA.sub.2 
is applied to the input of an inverter I.sub.4 which outputs an 
approximate tuning signal PA.sub.2 with positive logic. Signals PA.sub.1, 
A and PA.sub.2 are applied to the three inputs of an OR gate whose output 
is a signal A' which will be applied to the second input of gates 
PV.sub.p, with p varying from 1 to n, under the same conditions as signal 
A in FIG. 2 or FIG. 3. Similarly, the signal A is applied to the second 
input of AND gates PR.sub.p or inverting AND gates P'R.sub.p, with p 
varying from 1 to n. Furthermore, FIG. 4 shows that the tuning detector 30 
may possibly receive indications concerning the FM field and the AM field 
through divider bridges, respectively 12 and 13, which allow the field 
thresholds to be regulated independently in AM and FM. This conventional 
arrangement has, as will be recalled, a double advantage. In frequency 
modulation, this field indication is used for inhibiting the output of the 
tuning detector, i.e. in the presence of a field which is too weak, the 
output of the tuning detector will not produce at its output any signal 
representative of station tuning, whatever may be the situation at the 
level of the FM discriminator. It may of course be the same in AM. It 
should however be noted that AM receivers are not in general provided with 
a discriminator, i.e. that it is not possible to determine when there is 
exact station tuning. This is not in practice very troublesome, 
considering the very mediocre quality of this kind of transmission which 
is well received as soon as the field has a satisfactory level. This is 
the situation shown in FIG. 4: in the AM position, the tuning detector 
receives the AM field, but on the other hand a switch short circuits the 
two inputs of the tuning detector on the discriminator side, which causes 
the tuning detector 30 to output a signal A equal to 1 if the field is too 
weak and a signal A equal to 0 if the field reaches a satisfactory level. 
As for signals PA.sub.1 and PA.sub.2 they will always be equal to 1. 
Conventionally, we can say that a signal A=0 corresponding to a field 
exceeding a predetermined threshold, in AM without intervention of a 
discriminator, is a signal associated with presumed accurate station 
tuning. 
The operation can then be explained in the following way: if there is no 
station tuning, A is equal to 1, so a diode DR.sub.p (with p varying from 
1 to n) is lit up, in relation with the corresponding indication of the 
light needle control circuit (output S.sub.p at level 1). On the other 
hand, since A=0, as well as PA.sub.1 and PA.sub.2, the signal A' is equal 
to 0 and consequently diode DV.sub.p is not lit. There will for example in 
this case be a red light indication. In the presence of approximate tuning 
to a station, we have either PA.sub.1 =1, or PA.sub.2 =1 and consequently 
A'=1, and furthermore A=1, which means that the two diodes DR.sub.p and 
DV.sub.p are lit up simultaneously. This will correspond for example to a 
light indication orange in color (combination of green and red). In the 
case where there is station tuning, A=0 and A =1, so A'=1, which means 
that the diode DV.sub.p is alone lit up, which corresponds for example for 
the user to a light indication green in color. 
FIG. 5 shows one embodiment of a three color display using display elements 
each of which comprises three light emitting diodes. The display element 
of rank p thus comprises diodes D.sub.1p, D.sub.2p and D.sub.3p. The 
signals PA.sub.1 and PA.sub.2 supplied by the tuning detector 30 are 
respectively inverted in inverters I.sub.6 and I.sub.7. The signals 
PA.sub.1 and PA.sub.2 present at the output of the inverters I.sub.6 and 
I.sub.7, are applied to the two inputs of an OR gate 42 whose output 
signal A" is applied to the input of an inverter I.sub.8, whose output is 
then a signal A". Signal A present at the output of tuning detector 30 is 
inverted by an inverter I.sub.5 whose output is then the signal A. The 
signals A and A" are applied to the inputs of an AND gate 43. With the 
diodes being shown in the common cathode mode, each of the anodes thereof 
receives the output signal from an AND gate, namely P.sub.1p for diode 
D.sub.1p, P.sub.2p for diode D.sub.2p and P.sub.3p for diode D.sub.3p, 
with p varying from 1 to n. A first input of each of these AND gates 
P.sub.1p, P.sub.2p, P.sub.3p, receives the corresponding output signal 
S.sub.p from the light needle control circuit 20. Furthermore, the second 
input of each AND gate P.sub.1p (with p varying from 1 to n) receives the 
signal A outputted by the inverter I.sub.5, the second input of each gate 
P.sub.2p (with p varying from 1 to n) receives the signal present at the 
output of the AND gate 43, namely PA.sub.1 +PA.sub.2. A, and the second 
input of each gate P.sub.3p (with p varying from 1 to n) receives the 
signal A"=PA.sub.1 +PA.sub.2 present at the output of the OR gate 32. 
Consequently, for a logic level 1 signal present at the output S.sub.p of 
the light needle control circuit 20, the frequency light indication will 
be made in three modes. In the case where there is no station tuning, we 
have A=PA.sub.1 =PA.sub.2 =1, and consequently A"=1, and the AND gate 43 
has its two inputs at level 1 and it is diode D.sub.2p which is the only 
one to be lit up (A"=A=0). In the case of approximate station tuning, we 
have, either PA.sub.1 =0, or PA.sub.2 =0 and consequently A"=1, and 
furthermore A=1, and consequently A=0. Since A"=1, and so A"=0, the output 
of the AND gate 43 is equal to 0 and diode D.sub.3p is the only one to be 
lit up. Finally, in the case of exact tuning to a station, we have A=0 and 
PA.sub.1 and PA.sub.2 =1, which means that A=1, A"=0 and A"=1, so the 
output of the AND gate 43 is equal to 0; therefore, the diode D.sub.1p is 
the only one to be lit up. 
It will be noted, as in the case of FIG. 3, for obtaining operation with 
diodes whose anode is common it is sufficient to replace the AND gates 
P.sub.1p, P.sub.2p, and P.sub.3p by inverting AND gates. 
FIGS. 6 to 10 show the variations of the invention in series logic, that is 
to say that each light-emitting component receives on an electrode a 
signal corresponding to the logic state of the tuning detector and on the 
other electrode a signal corresponding to the logic state of the light 
needle control circuit 20. The light-emitting components must then be 
diodes or similar components having a preferential actuation direction. 
In FIG. 6 then, each display element IL.sub.p (with p varying from 1 to n) 
is formed of two light-emitting diodes DR.sub.p and DV.sub.p, whose 
cathodes are connected together. This common cathode receives the signal 
S.sub.p corresponding to the p.sup.th output of the light needle control 
circuit 20 with negative logic, that is in this case after inversion by an 
inverter I.sub.10+p. The diodes DR.sub.p (with p varying from 1 to n) 
receive at their anodes the signal A from the tuning detector. The diodes 
DV.sub.p (with p varying from 1 to n) receive at their anodes the signal A 
representing tuning in to a station in accordance with positive logic, 
i.e. after inversion by an inverter I.sub.9. The light indication of the 
level of the p.sup.th display element IL.sub.p is provided in the 
following way: for S.sub.p =1, we have S.sub.p =0; if there is no station 
tuning, we have A=1, and it is diode DR.sub.p which lights up; on the 
other hand, if there is station tuning, we have A=1 and it is diode 
DV.sub.p which lights up. The other diodes remain unlit in any case since 
we have S.sub.p, =1 (whatever p' is different from p), which means that 
the diodes DR.sub.p and DV.sub.p are either reversely biassed or receive 
at each of their electrodes a signal corresponding to a logic level 1. 
FIG. 7 shows a circuit equivalent to that of FIG. 6 in the case where it is 
the anodes of the diodes of the display element I'L.sub.p which are 
connected together. In this case, the common anode of the display element 
I'L.sub.p receives the output S.sub.p of the light needle control circuit 
20 (p varying from 1 to n). The cathode of each diode DV.sub.p (with p 
varying from 1 to n) receives the signal A from the tuning detector 30 and 
the cathode of each diode DR.sub.p (with p varying from 1 to n) receives 
the signal A from the tuning detector, in accordance with positive logic, 
i.e. after inversion by an inverter I.sub.10. The display of a frequency 
by the p.sup.th display element is then achieved in the following way: we 
have on the one hand S.sub.p =1, which means that, in the absence of 
tuning, A=0 and consequently diode D'R.sub.p is lit up whereas, in the 
presence of tuning, A=0 and it is the diode D'V.sub.p which is lit up; 
for the elements p' with p'.noteq.p, the outputs S.sub.p are at level 0 
and none of the diodes can light up. 
FIG. 8 shows the diagram of FIG. 6 adapted to a three color display by 
means of twin light-emitting diode display elements. The identical parts 
are shown with the same references. Furthermore, the tuning detector 30 
receives the FM discriminator and field signals under the same conditions 
as in FIGS. 4 and 5. The power supply for the cathodes of the diodes is 
provided by circuit 20 as in the case of FIG. 6 (inverters I.sub.10+p). 
The signals PA.sub.1, A and PA.sub.2 are respectively inverted by 
inverters I.sub.11, I.sub.12 and I.sub.13, whose outputs are applied to 
the three inputs of an OR gate 44 which outputs a signal A'=(PA.sub.1 
+A+PA.sub.2). Furthermore, the signal A present at the output of gate 
I.sub.12 is again inverted by inverter I.sub.14 which thus outputs a 
signal A. The purpose of this arrangement, apparently redundant, is to 
produce a better deinfed output level and this arrangement could also be 
applied to the cases of FIGS. 6 and 7 described above. Moreover, in the 
case where the tuning detector 30 does not involve TTL logic, the inputs 
of inverters I.sub.11 to I.sub.13 are connected to a power supply source 
+V through resistors R so as to fix logic level 1. Signal A is applied to 
the anode of each of the diodes DR.sub.p (with p varying from 1 to n). 
Signal A' is applied to the anode of each of the diodes DV.sub.p (with p 
varying from 1 to n). In the absence of station tuning, we have A=1 and 
A'=0 and so diode DR.sub.p lights up if S.sub.p is equal to 1. In the case 
of approximate tuning to a station, we still have A=1, but on the contrary 
either PA.sub.1 or PA.sub.2 is equal to 1 and so A' is itself equal to 1, 
which means that the diodes DR.sub.p and DV.sub.p are caused to light up 
simultaneously. With station tuning we have A=1 and so A"=1 and A =0, 
which means that diode DV.sub.p will be the only one lit up. 
FIG. 9 is a variation of FIG. 8 but corresponding to the cases already 
described in FIG. 7 where the anodes of the diodes of each display element 
are connected together. Thus, the OR gate 44 is replaced by an inverting 
OR gate 45 which also receives at its inputs the signals PA.sub.1, A and 
PA.sub.2. The cathode of each diode D'R.sub.p (with p varying from 1 to n) 
receives the signal A, whereas the cathode of each diode D'V.sub.p (with p 
varying from 1 to n) receives the signal A'=(PA.sub.1 +A+PA.sub.2) present 
at the output of the inverting OR gate 45. 
FIG. 10 shows a series logic variation in the case where each display 
element IL.sub.p " with p varying from 1 to n) comprises three 
light-emitting diodes D.sub.1p, D.sub.2p and D.sub.3p, whose cathodes are 
connected together and to the output S.sub.p of the light needle control 
circuit 20, with negative logic, i.e. after inversion by a gate 
I.sub.20+p. The signals PA.sub.1 and PA.sub.2 from the tuning detector are 
inverted respectively by inverters I.sub.16 and I.sub.17 whose outputs 
PA.sub.1 and PA.sub.2 are applied to an OR gate 46 whose output 
A"=PA.sub.1 +PA.sub.2 is applied in its turn to an inverter I.sub.18 so as 
to produce an output A". Furthermore, the signal A present at the output 
of the tuning detector 30 is inverted by an inverter I.sub.15 so as to 
output a signal A. The signals A and A" are applied to the inputs of an 
AND gate 47. The anode of each diode D.sub.1p (with p varying from 1 to n) 
receives the signal A, the anode of each diode D.sub.2p (with p varying 
from 1 to n) receives the output of the AND gate 47, i.e. (PA.sub.1 
+PA.sub.2). A, and the anode of each diode D.sub.3p (with p varying from 1 
to n) receives the signal A" present at the output of the OR gate 46. The 
light indication is then obtained according to an operating mode similar 
to that of FIG. 5. 
For operation of the diodes with commonly connected anodes, signals A, A' 
and (PA.sub.1 +PA.sub.2). A, applied to the diodes this time at their 
cathodes, must of course be replaced by their inversions. The AND gate 47 
becomes for example an inverting AND gate, and the output of inverter 
I.sub.18 is connected to the cathode of the third diode. 
FIG. 11 illustrates the different configurations of the input signals which 
the tuning detector 30 may receive. Since frequency modulation receivers 
are usually provided with a discriminator, the tuning detector 30 receives 
through a circuit 14 the zero of the FM discriminator. It also receives, 
in the case of three color display, the S curve of the FM discriminator, 
so as to be able to produce signals such as PA.sub.1 and PA.sub.2. In so 
far as amplitude modulation is concerned, it is also possible to use an 
amplitude modulation discriminator whose zero will be transmitted through 
a circuit 16, and for three color tuning display, the S curve of the 
discriminator through a circuit 17. There is also shown in FIG. 11 
switches for switching alternately in or out the AM discriminator and the 
FM discriminator with respect to the inputs of the tuning detector 30. 
Tuning detector 30 may also receive the FM field through a circuit 31 and 
the AM field through a circuit 32, a switch connected to the preceding one 
providing the switching. It will be recalled that these field indicators 
inhibit the indication of tuning or approximate tuning at the output of 
the tuning detector in the presence of a field which is weak. It is then a 
question of a device generally used but which is not indispensable within 
the scope of the invention. 
Furthermore, within the scope of the invention, a light needle control 
circuit may be used having discrete elements or integration of the whole 
of the electronic means may be provided.