Abstract:
An audio reproducing apparatus including first and second audio signal transmission paths each applied with a plurality of audio signals. Each of the first and second audio signal transmission paths has a selector for selecting one of the plurality of audio signals supplied thereto and a level controller for controlling the level of the selected audio signal. The first and second audio signal transmission paths are connected to first and second speaker units respectively each for converting the audio signal selected by the corresponding selector and whose level is controlled by the corresponding level controller into acoustic power.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an audio reproducing apparatus and more particularly to an audio reproducing apparatus of a type having a plurality of speaker output terminals and a switch for selectively applying an audio signal thereto. 
     2. Description of the Prior Art 
     It has been proposed in the art to have an audio reproducing apparatus so constructed that a change-over switch and two speaker output terminals are provided. An output signal of a main amplifier thereof is applicable to a speaker(s) disposed in a first room through one of the speaker output terminals or to a speaker(s) disposed in a second room through the other speaker output terminal selectively by the switch or applicable to the speakers in both the first and second rooms simultaneously. 
     However, in this conventional apparatus, since the output signal of the main amplifier is selectively applied to one of the speakers or both the speakers simultaneously in the first and second rooms, listeners in the first and second rooms cannot listen to different program or sound sources and further the sound volume of each of the speakers in both rooms becomes the same. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide an improved audio reproducing apparatus in which the aforementioned shortcomings and disadvantages of the prior art can be eliminated. 
     More specifically, it is an object of the present invention to provide an improved audio reproducing apparatus which is capable of supplying audio signals of different program sources to a plurality of speaker output terminals and further capable of adjusting the volume of the audio signals supplied to the output terminals independently. 
     According to an aspect of the present invention, an audio reproducing apparatus is comprised of a first audio signal transmission path to which a plurality of audio signals are supplied, a second audio signal transmission path to which the plurality of audio signals are supplied, transmitting circuits, first and second input selectors provided on the first and second audio signal transmission paths respectively each for selecting one of the plurality of audio signals applied to the corresponding path, first and second level controllers provided on the first and second audio signal transmission paths respectively each for controlling a level of the selected audio signal by the corresponding input selector, and first and second speaker units connected to the first and second audio signal transmission paths respectively each for receiving the selected audio signal. 
     The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of an illustrative embodiment thereof to be read in conjunction with the accompanying drawings, in which like reference numerals represent the same or similar parts and elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a systematic block diagram illustrating the construction of an embodiment of the audio reproducing apparatus according to the present invention; and 
     FIG. 2 is a plan view of rooms illustrating arrangement of audio and visual devices in the rooms in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings. 
     Referring to the drawings, FIG. 1 (formed of FIGS. 1A and 1B drawn on two sheets of drawings so as to permit the use of a suitably large scale) is a block diagram illustrating the construction of an embodiment of the audio reproducing apparatus according to the present invention. 
     The embodiment of the audio reproducing apparatus shown in FIG. 1 is exemplarily constructed so that the surround stereo sound system is provided in a first room  1  while a video signal can be reproduced and viewed by a video display device; such as a CRT (cathode ray tube) display device, independently in each of the first room  1  and a second room  2 . 
     Now, each of first and second audio signal transmission lines  10  and  20  shown in FIG. 1 has two lines for transmitting both audio signals of right and left channels respectively although only one line for transmitting one of the channels is shown in FIG. 1 merely to simplify the drawing. Therefore the explanation of this embodiment hereinafter will be made about one of the channels. 
     In FIG. 1, audio signals are respectively applied to first to n&#39;th audio signal input terminals  11   1 - 11   n , from audio devices such as an FM (frequency modulation) tuner(s), a satellite broadcasting tuner(s), a CD (compact disk) player(s) and a video disk player(s) or the like. One of the audio signals received at the input terminals  11   1 - 11   n  is selected by a switch circuit  12  for input selection. Then, the selected audio signal is applied to a stationary contact of a program source side of a switch circuit  13  for monitor selection through the first audio signal transmission line  10  on one hand and also applied to an output terminal  17  for recording on the other hand. A reproduced audio signal applied to a tape input terminal  18  from a cassette tape recorder or tape deck (not shown) is applied to a stationary contact of a tape recorder side of the switch circuit  13 . The audio signal selected by the switch circuit  13  is transmitted through a variable resistor  14  for volume or level control and a power amplifier  15  on the line  10  and applied to an output terminal  16  to thereby be applied to a speaker  19 L for a left channel or a speaker  19 R for a right channel. 
     In this case, the speakers  19 L and  19 R are disposed in the first room  1 . Namely, in the first room  1 , the speakers  19 L and  19 R are disposed at the left and right sides in front of a listener LSN 1  while speakers  39 L and  39 R are disposed at the left and right sides behind the listener LSN 1 , respectively, for example, as shown in FIG.  2 . Further, a CRT display device  49  is disposed between the speakers  19 L and  19 R, for example. 
     The audio signals received at the input terminals  11   1 - 11   n  are also applied to a switch circuit  22  for input selection and any one of the audio signals selected by the switch circuit  22  is applied to a switch circuit  23  for monitor selection on the second audio signal transmission line  20 . The switch circuit  23  selects one of the audio signals applied from the switch circuit  22  and the input terminal  18  and then the selected audio signal is transmitted on the second audio signal transmission line  20  to an output terminal  26  through a variable resistor  24  for volume or level control, a switch circuit  31 , a power amplifier  25  and a switch circuit  32 . The audio signal delivered to the output terminal  26  is then applied to a speaker  29 L for a left channel or a speaker  29 R for a right channel which are disposed in the second room  2 . 
     Namely, in the second room  2 , the speakers  29 L and  29 R are disposed at the left and right sides in front of a listener LSN 2  respectively and a CRT display device  59  is disposed between the speakers  29 L and  29 R, for example, as shown in FIG.  2 . 
     The amplifier  25  also acts to amplify the audio signal to be applied to the rear speakers  39 L and  39 R through an output terminal  36  in case of realizing the surround stereo sound system in the first room  1 . To this end, a surround processing circuit (SRND)  33  is provided in a manner that it extracts an audio signal of rear channels for the surround stereo sound on the basis of the selected audio signal from the switch circuit  12  and applies the extracted audio signal to the switch circuit  31  through a variable resistor  34  for volume or level control. The switch circuit  31  then selectively applies one of the audio signals from the variable resistors  34  and  24  to the amplifier  25 . 
     Now, as will be described later, the switch circuit  31  is ganged with the switch circuit  32  in a manner that when the movable contact of the switch circuit  31  is changed over to the stationary contact of the variable resistor  34  side, in case of the reproduction of the surround stereo sound, the movable contact of the switch circuit  32  is changed over to the stationary contact of the output terminal  36  side. Thus, when the reproduction of the surround stereo sound is selected, the amplifier  25  amplifies the audio signal supplied from the variable resistor  34  and supplies the amplified audio signal to the rear speakers  39 L and  39 R through the switch circuit  32  and the output terminal  36 . 
     Reproduced audio signals from such devices as a VTR(s) (video tape recorder) and a video disk player(s) etc. (not shown) are supplied to another set of first to n&#39;th video signal input terminals  41   1 - 41   n  and then applied to a switch circuit  42  for input selection. The switch circuit  42  then selects any one of the video signals received at the input terminals  41   1 - 41   n  and applies the selected video signal to an output terminal  46  through a first video signal transmission line  40  to thereby apply it to the CRT display device  49 . 
     The video signals received at the input terminals  41   1 - 41   n  are also applied to a switch circuit  52  for input selection and any one of the video signals selected by the switch circuit  52  is applied to an output terminal  56  through a second video signal transmission line  50  to thereby apply it to the CRT display device  59 . Now, the circuit configuration shown by a chain line block in FIG. 1 is installed as an audio reproducing apparatus  100  and disposed in the room  1 . 
     An infrared transmitter  91  for remotely controlling the apparatus  100  is provided in order to select the input audio signal transmitted on the first audio signal transmission line  10  and the first video signal transmission line  40  and to control the volume of the selected audio signal. An infrared transmitter  92  for remotely controlling the apparatus  100  is also provided in order to select the input audio signal transmitted on the second audio signal transmission line  20  and the second video signal transmission line  50  and to control the volume of the selected audio signal. To this end, though not shown, each of the transmitters  91  and  92  has a key(s) for selecting the inputted audio signal and a key(s) for controlling the volume of the selected audio signal. If the key of each of the transmitters is operated, each transmitter generates data DT for performing the control associated with the operated key and radiates the infrared ray subjected to the pulse modulation by the data DT. 
     A receiver  60  receives the infrared rays radiated from the transmitters  91  and  92  by its photo sensors  61  and  71 , respectively. The photo sensors  61  and  71  convert the received infrared rays into remote control signals to apply them to amplifiers  62  and  72  for wave-shaping, respectively. 
     In this case, the photo sensor  71  and the amplifier  72  are disposed in the second room  2 , but the photo sensor  61  and the amplifier  62  and the succeeding stages of the amplifiers  62  and  72  are located integrally with the audio reproducing apparatus  100 . 
     The remote control signals from the amplifiers  62  and  72  are applied to decoders  63  and  73  respectively to thereby decode the adjusting item of the data DT. The decoded data DT from the decoders  63  and  73  are applied to a system controller  64  having a microcomputer to thereby form control signals associated with the operated keys of the transmitters  91  and  92 , respectively. The control signals from the system controller  64  are applied to the switch circuits  12 ,  13 ,  22 ,  23 ,  31 ,  32 ,  42  and  52  to thereby control them. In this case, a pair of the switch circuits  12  and  42 , a pair of the switch circuits  22  and  52 , and a pair of the switch circuits  31  and  32 , are respectively changed over in a ganged manner. The control signals from the system controller  64  are also applied to motors  65  and  75 . The motor  65  cooperatively controls the variable resistors  14  and  34  in a ganged relation while the motor  75  controls the variable resistor  24 . 
     In this construction, if the key of the transmitter  91  is operated, the infrared rays modulated by the data DT corresponding to the operated key are transmitted and received by the photo sensor  61 , which in turn converts the infrared rays to the remote control signal and applies the same to the system controller  64  through the amplifier  62  and the decoder  63 . The system controller  64  then generates the control signal corresponding to the operated key to thereby control the switch circuits  12 ,  13 ,  31 ,  32  and  42  and the variable resistors  14  and  34  on the first audio and video signal transmission lines  10  and  40 . 
     Thus, the listener LSN 1  in the first room  1  can not only select any one of the program sources applied to the input terminals  11   1 - 11   n ,  18  and  41   1 - 41   n  but also control the volume of the selected program source by operating the key of the transmitter  91 . The listener LSN 1  in the first room  1  also can select the surround stereo sound by operating the switch circuits  31  and  32  so as to drive the rear speakers  39 L and  39 R by the extracted audio signals of the rear sound. 
     Also, if the key of the transmitter  92  is operated, the infrared rays modulated by the data DT corresponding to the operated key is transmitted and received by the photo sensor  71 , which in turn converts the infrared rays to the remote control signal and applies the same to the system controller  64  through the decoder  73 . The system controller  64  then generates the control signal corresponding to the operated key to thereby control the switch circuits  22 ,  23 ,  31 ,  32  and  52  and the variable resistor  24  on the second audio and video signal transmission lines  20  and  50 . 
     Thus, the listener LSN 2  in the second room  2  can not only select any one of the program sources applied to the input terminals  11   1 - 11   n ,  18  and  41   1 - 41   n  but also control the volume of the selected program source by operating the key of the transmitter  92 . 
     Accordingly, in the present invention, the audio signal and also the video signal can be reproduced in each of the rooms  1  and  2 . Further, for a plurality of program sources there are provided the first and second audio signal transmission lines  10  and  20 , and the switch circuits  12  and  22  capable of selecting the program sources independently to each other and the variable resistors  14  and  24  for controlling the volume of the selected program source are provided on the audio signal transmission lines  10  and  20 , respectively. Thus, by providing only one audio reproducing apparatus  100  according to the present invention, two listeners LSN 1  and LSN 2  can not only simultaneously and independently select the program source but also control independently the volume of the selected program source. 
     Further, the selection of the program source and the adjusting of the volume of the selected program source can be performed by the remote controller. 
     The main amplifier  25  acts not only as an amplifier for the rear channel of the surround stereo sound but also as an amplifier for the second room  2 , so that there is no necessity of providing two amplifiers to thereby make the cost of the apparatus cheap. 
     Further, the video image can be reproduced simultaneously with the reproduction of the audio signal in a manner that different program sources can be viewed by the CRT display devices  49  and  59  since the plurality of program sources received at the input terminals  41   1 - 41   n  are applied to the first and second video signal transmission lines  46  and  56  through the switch circuits  42  and  52 . 
     Now, the above-described embodiment uses the electronic switches which are controlled by the control signal such as the switches  12 ,  13 ,  22 ,  23 ,  32 ,  42  and  52  but may instead use such mechanical switches as those rotated by motors driven by the control signals instead of the electronic switches. Further, such attenuators of electronic control type as those controlled by the control signals may be used instead of the variable resistors  14 ,  24  and  34 . 
     Instead of the power amplifiers  15  and  25 , buffer amplifiers may be used and other power amplifiers may be provided outside of the apparatus. Further, an amplifier of BTL connection may be provided instead of the amplifiers  15  and  25  in a manner that the amplifier acts as an amplifier for the room  1  or  2  when the listeners listen to the music etc. in the room  1  or  2  and the BTL connection amplifier is divided into two amplifiers  15  and  25  for the rooms  1  and  2  respectively when the listeners listen to the music etc. in both rooms simultaneously. 
     The apparatus may be modified so as to be able to adjust the DSP as well as the selection of the program sources and the adjusting of the volume. 
     Therefore, according to the present invention, the first and second audio signal transmission lines  10  and  20  are provided each for receiving the plurality of program sources, and on the lines  10  and  22 , the switch circuits  12  and  22  are respectively provided for independently selecting the inputted program sources. Further the variable resistors  14  and  24  for controlling the volume of the selected sources are provided respectively, so that by providing only one audio reproducing apparatus  100  according to the present invention, two listeners LSN 1  and LSN 2  can not only simultaneously and independently select the program source but also control independently the volume of the selected program source. 
     Further, the selection of the program source and the adjusting of the volume of the selected program source can be performed by the remote controller. 
     The main amplifier  25  acts not only as an amplifier for the rear channel of the surround stereo sound but also as an amplifier for the second room  2 , so that there is no necessity of providing two amplifiers to thereby make the cost of the apparatus cheap. 
     Further, the video image can be reproduced simultaneously with the reproduction of the audio signal in a manner that different program sources can be viewed by the CRT display devices  49  and  59  simultaneously. 
     Having described the preferred embodiment of theinvention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiment and that various changes and modifications thereof could be effected by those skilled in the art without departing from the spirit or scope of the novel concepts of the invention as defined in the appended claims.