Sound multiplex broadcast receiver and method of controlling display thereof

In a sound multiplex broadcast system employing sound multiple signals having a plurality of sound multiplex modes and a display control method therefor, there are detected kinds of sound multiplex mode of sound multiple signals received by the receiver, a sound multiplex mode is set, a demodulated sound output signal of a mode determined according to the mode detection signals and the mode setting signal is selected from demodulated sound output signals attained by demodulating the received sound multiple signals so as to be supplied to a sound output unit, and a kind of sound multiplex mode of the demodulated sound output signal thus selected is displayed on a display unit.

BACKGROUND OF THE INVENTION 
The present invention relates to a multiplex broadcast receiver having a 
sound multiplex demodulator circuit, and in particular, to a sound 
multiplex broadcast receiver and a method of controlling display thereof 
in which modes of sound output signals from the receiver can be displayed. 
In a sound multiplex broadcast receiver (for example, a television 
receiver) for use in a sound multiplex broadcast system of the United 
States of America (U.S.) and/or Japan, display of a sound multiplex 
receiving mode according to detection of presence or absence of a 
broadcast sound multiple signal and display of a sound multiplex setting 
mode established by the user are controlled in general by a light-emitting 
diode or a switching device as described, for example, in page 34 of the 
"Television Technology", Nov. 1978. However, recently, thanks to adoption 
of a cathode-ray tube (CRT) screen for the display operations, the 
receiving and setting modes above are displayed on the CRT display for the 
control operations thereof. 
Moreover, in the receiver of this kind, the state of mode is not displayed 
for the sound output signal from the receiver. Consequently, to 
discriminate the mode of the output signal, the user has been required to 
check presence or absence of the display of the sound multiplex reception 
mode and the display of the mode established by the user. 
SUMMARY OF THE INVENTION 
In this connection, in the sound multiplex broadcast receiver, when the 
sound multiplex mode set by the user is not being transmitted, since the 
sound demodulation output signal is missing, a mode change-over or switch 
operation is automatically executed to another sound output mode under 
transmission. In consequence, when the sound multiplex mode set by the 
user is not being transmitted, the state of mode set by the user does not 
match that of the sound output signal from the receiver. This leads to a 
disadvantage that the state of mode cannot be discriminated for the sound 
output signal from the receiver. 
The discrimination of the sound output signal from the receiver is easily 
accomplished if only two kinds of sound channels are employed like in the 
case of the sound multiplex broadcast system of Japan. However, this may 
not be possible when there are adopted a plurality of sound channels, for 
example, in the sound multiplex broadcast system of the United States. 
It is therefore an object of the present invention is to provide a sound 
multiplex broadcast receiver and a method of controlling display thereof 
in which the drawbacks of the conventional sound multiplex broadcast 
receiver are removed. 
Another object of the present invention is to provide a sound multiplex 
broadcast receiver and a method of controlling display thereof in which 
the kinds of mode of sound output signals from the receiver, which have 
been conventionally discriminated by the user, can be automatically 
detected to be accordingly displayed. 
According to an aspect of the present invention, a sound multiplex 
broadcast receiver for use in a sound multiplex broadcast system employing 
sound multiple signals having a plurality of sound multiplex modes 
includes a mode detecting unit for detecting kinds of sound multiplex mode 
of sound multiple signals received by the receiver and outputting mode 
detection signals, a mode setting unit for setting a sound multiplex mode 
and outputting a mode setting signal, a selecting unit for selecting, from 
demodulated sound output signals attained by demodulating the received 
sound multiple signals, a demodulated sound output signal of a mode 
determined according to the mode detection signals and the mode setting 
signal and supplying the selected signal to a sound output unit, and a 
display unit capable of displaying thereon a kind of sound multiplex mode 
of the demodulated sound output signal thus selected. 
That is, in the configuration according to the present invention, in order 
to achieve the object above, the kinds of mode of sound output signals 
from the receiver are automatically decided depending on a signal obtained 
by sensing sound reception modes and a mode setting signal established by 
the user, thereby presenting the kind of mode on a display unit. 
Namely, the change-over operation of the sound output signals from the 
receiver is supervised by the detection signal indicating the sound 
reception modes and the mode setting signal specified by the user. 
Consequently, the types of mode of sound output signals from the receiver 
can be decided depending on the control signal for the change-over 
operation so as to be displayed on the display unit, which enables the 
user to automatically determine the kinds of mode of the sound output 
signals. 
As above, according to the present invention, the decision of the sound 
modes of sound output signals from the sound multiplex broadcast receiver, 
which have been heretofore accomplished by the user, can be automatically 
displayed by the receiver. This reduces the load imposed on the user and 
makes it possible to correctly display the sound output modes, thereby 
highly improving the usability of the receiver for the user. 
As an example, the display unit displays, in response to a channel 
change-over operation of the sound multiplex broadcast, a kind of sound 
multiplex mode of the demodulated sound output signal thus selected. 
In another example, the display unit displays, in response to a change in 
the sound multiplex mode of the demodulated sound output signal thus 
selected, a changed kind of sound multiplex mode of the demodulated sound 
output signal thus selected. 
As still another example, there is further disposed a unit for indicating a 
mode display such that the display unit displays, in response to the 
indication of the mode display, a kind of sound multiplex mode of the 
demodulated sound output signal thus selected. 
As further another example, the display unit is capable of further 
displaying a kind of the sound multiplex mode thus set by the user. 
As another example, the display unit is capable of further displaying kinds 
of sound multiplex mode of the received sound multiple signals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the accompanying drawings, description will be given of 
embodiments of the sound multiplex broadcast receiver according to the 
present invention. In these embodiments, the present invention is applied 
to a television receiver of the sound multiplex broadcast system. 
FIG. 1 shows in a block diagram the overall structure of a television 
receiver of the sound multiplex broadcast system according to the present 
invention. FIG. 2 is a block diagram showing the constitution of the main 
sections of the television receiver. In the construction of FIG. 1, an 
antenna 1 receives a radio wave of the television broadcast system and 
then resultantly supplies a radio frequency (RF) signal to a tuner 2. The 
tuner 2 is supervised by a control circuit 7 to transform an RF signal of 
an arbitrary channel selected by the user into an inter-frequency. 
A picture inter-frequency/sound inter-frequency (PIF/SIF) circuit 3 
amplifies and detects PIF and SIF signals delivered from the tuner 2 to 
obtain a video signal and a sound multiple signal. A video signal 
processing circuit 4 processes under control of the controller 7 the video 
signal fed from the PIF/SIF circuit and a display signal supplied from a 
display control circuit 8 to send the video signal to a cathoderay tube 
(CRT) 5 as a display unit, thereby presenting an image on the display unit 
5. 
A sound multiplex mode setting unit 6 sets a sound multiplex mode selected 
by the user and generally includes a light receiving section for receiving 
an infrared light denoting a sound multiplex mode sent from a key switch 
unit or a remote controller to set a sound multiplex mode. 
The unit 6 supplies the control circuit 7 with a mode setting signal 
designating a sound multiplex mode established by the keyboard or the 
remote controller and a (channel selection) signal denoting a channel 
selected thereby. 
The controller 7 controls the receiving channel of the tuner 2 in response 
to the channel selection signal from the mode setting unit 6 and 
supervises the signal processing in the video signal processing circuit 4, 
a sound multiplex processing circuit 10, and a sound signal processing 
circuit 11. Moreover, the controller 7 operates in response to the mode 
setting signal and the receiving mode detection signal which is produced 
from the circuit 10 to supply display signals via the display controller 8 
to the circuit 4 and a second display unit 9, for example, display 
elements including light-emitting diodes. As shown in FIG. 2, the circuit 
4 and the CRT 5 constitute a first display unit 25. The display controller 
8 displays on the CRT 5, in response to a display signal from the 
controller 7, such items as the kind of the sound multiplex mode (setting 
mode) instructed by the user. 
In addition, the video signal processing circuit supplies the CRT 5 with a 
display signal according to a reception mode detection signal transmitted 
via the display controller 8 from the controller 7 and a display signal 
indicating a mode of sound output signals created from a speaker. As a 
result, the kind of the sound multiplex mode (reception mode) received 
from the tuner 2 and the type of mode of sound output signals from the 
speaker can be displayed. 
As shown in FIG. 2, the sound multiple signal processing circuit 10 
includes a sound multiplex mode detector circuit 22, receiving sound 
multiple signals from the PIF/SIF circuit 3 via an input terminal 21 and 
detecting the reception sound multiplex mode (reception mode) of the 
received signals, and transmitting a reception mode detection signal to 
the controller 7 and a sound signal demodulation switching circuit 23 for 
demodulating the received signals, selecting in response to a control 
signal from the controller 7 a particular sound channel signal from the 
demodulated sound channel signals, and outputting the selected signal via 
an output terminal 24 to the sound signal processing circuit 11. 
The circuit 11 processes the sound channel signal delivered from the 
circuit 10 and then sends the resultant signals as a sound output signal 
to a sound output circuit 12. The circuit 12 in turn drives a speaker 
integrated therein according to the sound output signal. 
In this embodiment, the CRT 5 is assumed to be a display screen of a 
television receiver and the second display unit 9 is considered as, for 
example, display elements such as a plurality of light-emitting diodes 
(LEDs). The number of LEDs is assumed to correspond to that of the kinds 
of mode of the sound multiplex broadcast. Moreover, the second display 
unit 9 may naturally be included in the display screen (CRT 5) of the 
television receiver. In such a case, the reception mode is also presented 
on the CRT 5. 
Next, description will be given of the operation when the present invention 
is applied to a television receiver conforming to the sound multiplex 
broadcast system of the U.S. 
The sound channel signals in this case include three kinds of signals, 
namely, a first sound channel signal (monaural), a second sound channel 
signal (stereo), and a third sound channel signal (second audio program). 
The first, second, and third sound channel signals stand for the 
demodulation signals of the first, second, and third sound multiplex 
modes, respectively. 
Referring to FIG. 2, first, when the user operates the remote controller of 
the key switch unit for a sound multiplex setting mode screen, the screen 
is presented on the CRT 5 of the first display unit 25. In this situation, 
when a predetermined key is activated in the remote controller or the key 
switch to conduct a conversational operation with the display screen, a 
sound multiplex mode desired by the user is set in the sound multiplex 
mode setting unit 6. Moreover, the kind of the established mode is 
displayed on the CRT 5. After the mode is thus determined, when the user 
selects a television broadcast channel (station), there is preferentially 
outputted the sound signal associated with the selected mode. Furthermore, 
in a case where the mode thus selected is missing in the television 
broadcast channel, there is outputted a sound signal in a mode of the 
subsequent grade determined by the control circuit 7. If the sound 
broadcast of the subsequent mode is missing, a sound signal of a mode next 
to the subsequent mode is outputted. 
Referring now to the flowchart of FIG. 3, description will be given of an 
example of the operation of the controller 7 achieving the selection of 
the mode of sound output signals and the control of display of the 
selected mode. The processing operation of FIG. 3 is achieved in an 
appropriate manner, for example, at a fixed interval of time. The control 
circuit 7 may include a micro computer. 
In the flowchart, a letter A denotes a setting mode selected by the user, a 
letter B indicates a mode of the received sound multiplex signal, a letter 
C stands for display data for presenting a reception mode, a letter D 
designates display data for displaying a mode (sound output mode or 
operation state) of sound output signals from the receiver, and a letter E 
indicates a kind of sound output mode of the receiver. 
First, according to the mode setting signal, the setting mode selected by 
the user is detected (step 100) and then the mode of the received signal 
is recognized according to the reception mode detection signal (step 102). 
Next, a check is made to decide whether or not the setting mode A is 
related to "monaural" (step 104). If this is the case, the system does not 
set the display data C for the reception mode. Namely, any indication is 
not made on the second display unit 9 for the setting mode. 
In this case, consequently, "monaural" is set as the sound output mode E of 
the receiver and a control signal is fed to the switching circuit 23 to 
select a signal of the monaural sound channel. Moreover, the system does 
not set the display data D for the sound output mode (steps 108 and 110). 
In the step 104, if it is determined that the setting mode is other than 
"monaural", a check is made to determine whether or not the mode B of the 
received signal is "monaural" (step 112). If this is the case, control is 
passed to a step 106; otherwise, judgement is conducted to decide whether 
or not the mode is "stereo" and "SAP" (step 114). If this is the case, the 
system sets, for example, "ST/SA" as the display data C of the reception 
mode (step 116). Subsequently, whether or not the setting mode A is 
"stereo" is judged (step 118). If the mode A is not "stereo" SAP is set as 
the sound output mode E of the receiver in this case such that the switch 
circuit 23 selects the signal of the SAP sound channel. Moreover, an 
indication, for example, "SAP" is set as the display data D of the sound 
output mode (steps 120 and 122). 
On the other hand, in the step 118, if the setting mode A is decided as 
"stereo", "stereo" is set as the sound output mode E of the receiver such 
that the switch circuit 23 selects the signal of the stereo sound channel. 
Furthermore, the system sets, for example, "STEREO" as the display data D 
of the sound output mode (steps 128 and 130). 
In the step 114, if it determined that the mode B of the received signal is 
other than the condition including "stereo" and "SAP", a check is made to 
decide whether or not the mode B of the received signal is "stereo" (step 
124). If this is the case, for example, "ST" is set as the display data C 
of the reception mode (step 126). Next, control is transferred to the 
steps 128 and. 130. 
In the step 124, if the mode B of the received signal is other than 
"stereo" the mode of the received signal is assumed to be "SAP" . For 
example, "SA" is set as the display data C of the received signal (step 
132). Next, a check is made to determine whether or not the setting mode A 
is "stereo" (step 134). If this is the case, control is passed to the 
steps 108 and 110; otherwise, the processing proceeds to the steps 120 and 
122. 
As above, based on the setting mode of the user and the mode of the 
received signal, the display data C of the reception mode and the display 
data D of the sound output mode are established. Moreover, a control 
signal is supplied to the switch circuit 23 so as to determine whether or 
not there exists a display instruction for the display data C and D in a 
step 136. If this is the case, display signals respectively representing 
the display data C and D are sent via the display control circuit 8 to the 
video signal processing circuit 4, thereby displaying the data C and D on 
the screen of the CRT 5, for example, for a fixed period of time (step 
138). Otherwise, the display operation is postponed until a display 
instruction is received. 
FIG. 4 shows an example of display on the screen of the CRT 5 in which, for 
example, when the mode B of the received signal is "stereo" and "SAP" and 
the setting mode A of the use is "stereo" "ST/SA" and "STEREO" are 
presented respectively as the display data C and D on the screen as shown 
in (h). In this diagram, letters G and H respectively stand for a channel 
number and a point of time, which may also be displayed together with the 
display data C and D. In this example, the setting mode A of the user 
detected in the step 100 is sent as a display signal designating the 
display data F from the control circuit 7 via the display controller 8 to 
the second display unit 9 for the display thereof. 
FIG. 5 shows an example of the second display unit 9 including LEDs 50 and 
52 for displaying indications of setting modes. For example, when "stereo" 
and "SAP" are specified as the setting modes, these items are displayed on 
the LEDs 50 and 52, respectively. In addition, there may be further 
disposed an LED for presenting, when the setting mode is "monaural" the 
indication thereof. These LEDs may be continuously illuminated when the 
corresponding modes are being set, respectively. 
The display instructions include an instruction to be outputted from the 
controller 7 in response to a channel switch (selection) by the user, an 
instruction to be issued therefrom in response to detection of a setting 
mode change-over by the user, and an instruction to be outputted in 
response to an operation of a recall key or the like of the remote 
controller or the key switches. 
In the example above, the display data C and D and the display data F of 
the setting mode are presented respectively on the CRT and LEDs. However, 
all of the data items may be displayed on the CRT or LEDs or it may also 
be possible to present the display data C of the reception mode and the 
other data on the LEDs and the CRT, respectively. 
Description will next be given of an example of operation of the embodiment 
thus configured. 
Assume that, for example, a stereo broadcast and an SAP broadcast are 
transmitted in a sound multiplex broadcast as a television channel 
broadcast for the user and the user sets "SAP" as the sound multiplex 
mode. When the user selects the station from the remote controller or the 
like, the kinds of mode of the reception signal are determined by the 
sound multiplex mode detector 22 to thereby produce an output signal. In 
response to the signal, the sound reception modes are displayed by the 
first display unit 25. Namely, since there are two modes "stereo" and 
"SAP" of the reception signal, in response to a display signal emitted 
from the controller 7 according to the detection signal of the reception 
modes from the detector 22, the video signal processing circuit 4 
supervises the CRT 5 to present "ST/SA" in the area C ((h) of FIG. 4)) of 
the screen for a predetermined period of time. With this provision, the 
stereo and SAP broadcast services are visually notified to the user. In 
this regard, when the sound multiplex broadcast is missing, the system 
does not display any image in the area C. 
Moreover, the control circuit 7 is being supplied from the sound multiplex 
mode setting unit 6 with a mode setting signal designating "SAP" selected 
as the sound multiplex mode by the user. The circuit 7 controls the sound 
signal demodulation change-over or switch circuit 23 according to the 
detection signal of reception modes and the mode setting signal. Assuming 
that sound channel signals "monaural, "stereo" and , "SAP" are being 
inputted from the input terminal 21 to the circuit 23, the controller 7 
supervises the circuit 23 to output a signal of the SAP sound channel. At 
the same time, the controller 7 sends, in order to visually report the 
output of SAP sound to the user, a display signal via the display control 
circuit 8 to the video signal processing circuit 4, thereby presenting 
"SAP" in the screen area D of the CRT for a preset period of time. 
Furthermore, the control circuit 7 supplies, in response to the mode 
setting signal, a display signal to the circuit 8 to drive the second 
display unit 9 so as to illuminate the LED 52 for "SAP" which notifies the 
user that the SAP mode is set by the user. In this situation, the LED 50 
for "stereo" is off. 
When the SAP broadcast is interrupted in this case (i.e. when "SAP" is set 
as the mode of sound multiplex broadcast), the controller recognizes the 
condition according to an output signal from the mode detector 22 and then 
supervises the circuit 4 to automatically achieve a change-over operation 
so as to select the stereo sound output. Simultaneously, the controller 7 
causes the CRT 5 to display letters "STEREO" in the predetermined area D 
on the display screen thereof. In this case, the display data C of the 
reception mode may be simultaneously displayed in the area C. 
Thereafter, following the SAP broadcast, when the stereo broadcast is 
interrupted, the controller 7 similarly conducts the control operation to 
automatically select the monaural sound output. In this operation, "MONO" 
may be displayed as the sound output mode of the receiver on the display 
screen of the CRT 5 for a preset period of time. Alternatively, it may 
also be possible that the system does not display any indication. 
Furthermore, like in the case above, the display data C may be presented at 
the same time. 
As a result of the operations, the state of mode of the sound output signal 
of the receiver can be automatically detected to be accordingly displayed. 
In this connection, it is naturally possible to continuously present the 
sound output mode. However, in association therewith, visibility of the 
screen image may be deteriorated in an ordinary operation of the screen. 
In the embodiment, consequently, the mode display is automatically 
accomplished only when a station is selected or when the sound output mode 
is changed. 
In addition, in order for the user to confirm at an arbitrary point of time 
the current state of mode of the sound output signal, the system may be 
configured such that the selection channel number and the sound output 
mode can be presented in response to a request from the user, for example, 
by operating the recall key or the like of the remote controller. 
The display letters (symbols) of display data C and D have been shown by 
way of example in this embodiment, namely, any display characters 
(symbols) may be utilized. 
Moreover, as data to be displayed as above, there may be adopted only the 
display data D; furthermore, only a combination of display data C and D or 
a combination of display data C and F may be employed. 
According to the present invention, the discrimination of sound modes of 
the sound output signals from the sound multiplex broadcast receiver, 
which has been conventionally achieved by the user, can be automatically 
conducted by the receiver so as to display the sound mode. Consequently, 
the load imposed on the user is minimized and the sound output mode can be 
appropriately displayed, which remarkably improves the usability of the 
receiver for the user. 
While particular embodiments of the invention have been shown and 
described, it will be obvious to those skilled in the art that various 
changes and modifications may be made without departing from the present 
invention in its broader aspects.