Imager connected to external processor by single cable comprising two coaxial cables and four signal lines

An image pickup system in which the number of cables for connecting a video camera, a headset and a personal computer are reduced. The video camera and an expansion board attached to the personal computer are connected by a single cable through 8-pin DIN connectors. Through this cable, a synchronizing signal, a control signal, and a sound signal (which is sent from an external source) are transmitted to the video camera from the expansion board. Further, a headset (having earphones and a microphone) worn by the user of the video camera is connected to the video camera through another cable. Through this cable, a sound signal from the external source is transmitted to the earphones, while a sound signal from the user input through the microphone is sent to the expansion board via the video camera and the cable for connecting the camera and the board.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an image pickup apparatus suitably used
 for a videoconference system, and an image processing apparatus for
 processing picked-up video images. The invention is also concerned with an
 image pickup system formed by connecting the above image pickup apparatus
 and the image processing apparatus.
 2. Related Background Art
 Hitherto, as a videoconference system using the above type of apparatus,
 conference-type large-sized cabinet-accommodated systems, and cart-type
 systems housed in a wheeled cart are the mainstream. Along with widespread
 use of computers (personal computers), desktop videoconference systems
 using personal computers have appeared and are currently in the limelight.
 This system is constructed, as illustrated in FIG. 10, of a video camera
 101, an expansion board 102 for a personal computer (which incorporates
 sound and video images, performs data expansion and compression, and
 executes communication control), a headset 103, and software 104.
 FIG. 11 is an external view illustrating the construction of a desktop
 videoconference system formed by connecting the above elements 101 through
 104 to a personal computer. In FIG. 11, the system further includes the
 main unit 105 of the personal computer, a personal computer monitor 106, a
 keyboard 107, and a mouse 108.
 Electrical connection of the above-described components is shown in FIG.
 12. An explanation will now be given with reference to FIG. 12 of an
 example in which the communication camera VC-C1 (which was invented by the
 present inventor and became commercially available in 1994) is used as the
 video camera 101.
 The video camera 101 is equipped with a pan-tilt mechanism, a video output,
 an S-video output, a sound line output, a direct-current (DC) power input,
 and an RS232C control terminal (none shown). For supplying DC power to the
 video camera 101, a DC power supply line (a DC power supply and a ground)
 110 is first connected to the video camera 101 via an AC adapter 109.
 Among the video outputs of the video camera 101, for example, the S-video
 output terminal, is then connected to an S video input terminal provided
 for the expansion board 102 via a video cable 111. Subsequently, for
 controlling various functions of the video camera 101, such as pan, tilt,
 and zoom, an RS232C terminal of the personal computer unit 105 and an
 RS232C terminal of the video camera 101 are connected by the use of an
 RS232C cable 113. With respect to sound, since a microphone is not built
 into the video camera 101, a headset 103 having a microphone and a speaker
 is connected to the expansion board 102 using a headset cable 112.
 In this manner, electrical connections with respect to (1) a video camera
 power supply, (2) video signals, (3) control signals, and (4) sound
 signals have been completed. After the personal computer is switched on, a
 predetermined software program is run to enable this system to function as
 a desktop videoconference system. Operation of the videoconference and
 connection of the system to a communication line, such as an integrated
 services digital network (ISDN), are irrelevant to the present invention,
 and an explanation thereof will thus be omitted.
 The number of connecting cables used for establishing the above-described
 electrical connections can be summarized as follows:
 (1) two power supply cables, i.e., a DC power supply and a ground (GND);
 (2) four video cables, i.e., Y and C video signal cables and the respective
 GNDs;
 (3) eight RS232C cables, (however, the minimum number in synchronous serial
 transmission is four, i.e., Tx, Rx, clock and GND); and between the
 headset 103 and the expansion board 102,
 (4) three headset cables, i.e., a microphone signal line, a speaker signal
 line, and a GND.
 Accordingly, four types of cables and at least 13 signal lines are required
 in total.
 However, the aforedescribed conventional system presents the following
 problems.
 (1) The three cables, such as the power supply cable 110, the video cable
 111, and the RS232C cable 113 are separately connected to the video camera
 101, thereby impairing the external appearance from an aesthetic point of
 view and also lowering reliability. In short, a disconnection of any one
 of the cables will spoil the operation.
 (2) The two cables, such as the video cable 111 and the headset cable 112,
 are also separately connected to the expansion board 102, thereby marring
 the external appearance of the back side of the personal computer unit 105
 at which the connecting portions with the above cables 111 and 112 are
 disposed.
 (3) The RS232C cable 113 for controlling the video camera 101 is
 unfavorably connected to the RS232C terminal of the personal computer unit
 105 which may be required for connecting to another device, for example, a
 modem or a printer.
 (4) The headset 103 is preferably disconnected and stored in, for example,
 a drawer when not in use from a sanitary point of view. The headset cable
 112, however, is connected to the back side of the personal computer
 through the expansion board 102 and is not easy to disconnect.
 (5) The AC adapter 109 is not always coupled to the same AC power supply
 line as the line for the personal computer unit 105. It is thus necessary
 to check that power is positively supplied to the AC adapter 109 when AC
 power is supplied to the computer unit 105.
 SUMMARY OF THE INVENTION
 Accordingly, it is an object of the present invention to provide an image
 pickup apparatus, an image processing apparatus, and an image pickup
 system, all of which are suitable for desktop videoconferencing, free from
 the aforedescribed problems.
 In order to achieve the above object, according to a first aspect of the
 present invention, there is provided an image pickup apparatus comprising:
 image pickup means for picking up an image of a subject and outputting a
 video image signal; a first terminal for receiving a first control signal;
 a second terminal for receiving a synchronizing signal; first control
 means for generating a second control signal based on the received first
 control signal and the synchronizing signal, and also for performing
 overall control; adding means for adding the second control signal to the
 video image signal; a third terminal for outputting the video image signal
 to which the second control signal is added; and a fourth terminal for
 receiving a power supply voltage.
 According to a second aspect of the present invention, there is provided an
 image processing apparatus comprising: a first terminal for receiving a
 video image signal; image processing means for processing the received
 video image signal; synchronizing-signal generating means for generating a
 synchronizing signal; a second terminal for outputting the synchronizing
 signal; second control means for generating a first control signal based
 on the synchronizing signal, and also for performing overall control; a
 third terminal for outputting the first control signal to the exterior;
 power supply means for supplying a power supply voltage; and a fourth
 terminal for outputting the power supply voltage.
 According to a third aspect of the present invention, there is provided an
 image pickup system comprising: an image pickup apparatus including image
 pickup means for picking up an image of a subject and outputting a video
 image signal, a first terminal for receiving a first control signal, a
 second terminal for receiving a synchronizing signal, first control means
 for generating a second control signal based on the received first control
 signal and the synchronizing signal, and also for performing overall
 control, adding means for adding the second control signal to the video
 image signal, a third terminal for outputting the video image signal to
 which the second control signal is added, a fourth terminal for receiving
 a power supply voltage, and first connector means having the first through
 fourth terminals; an image processing apparatus including a fifth terminal
 for receiving a video image signal, image processing means for processing
 the received video image signal, synchronizing-signal generating means for
 generating a synchronizing signal, a sixth terminal for outputting the
 synchronizing signal, second control means for generating a first control
 signal based on the synchronizing signal, and also for performing overall
 control, a seventh terminal for outputting the first control signal to the
 exterior, power supply means for supplying a power supply voltage, an
 eighth terminal for outputting the power supply voltage, and second
 connector means having the fifth through eighth terminals; and a cable
 having at both ends third and fourth connector means respectively
 connected to the first and second connector means so as to couple a
 corresponding pair of terminals respectively selected from the first
 through fourth terminals and the fifth through eighth terminals.
 In the image pickup apparatus according to the first aspect of the present
 invention, the second control signal generated by the first control means
 is superimposed on a video image signal obtained by picking up an image of
 a subject by the image pickup means, and then, the superimposed signal is
 output from the third terminal. The first control means produces the
 second control signal based on the first control signal and the
 synchronizing signal input from the first and second terminals,
 respectively. The respective means receive the power supply via the fourth
 terminal.
 In the image processing apparatus according to the second aspect of the
 present invention, the video image signal input through the fifth terminal
 is processed by the image processing means. Moreover, the synchronizing
 signal generated by the synchronizing-signal generating means is output
 from the sixth terminal, and the second control means generates the first
 control signal based on the synchronizing signal and outputs it from the
 seventh terminal. The power supply means outputs a power supply voltage
 through the eighth terminal.
 The image pickup system according to a further aspect of the present
 invention operates in the following manner. In the image pickup apparatus,
 the second control signal generated by the control means is superimposed
 on a video image signal obtained by picking up an image of a subject by
 the image pickup means, and then, the superimposed signal is transmitted
 to the image processing apparatus from the third terminal through the
 cable. The first control means receives through the first and second
 terminals the first control signal and the synchronizing signal,
 respectively, sent from the image processing apparatus via the cable, and
 generates the second control signal based on the first control signal and
 the synchronizing signal. Additionally, a power supply voltage from the
 image processing apparatus is fed to the image pickup apparatus via the
 fourth terminal. In the image processing apparatus, a video image signal
 input from the image pickup apparatus through the fifth terminal via the
 cable is processed in the image processing means. Further, the
 synchronizing signal produced in the synchronizing-signal generating means
 is output from the sixth terminal and sent to the image pickup apparatus
 via the cable, and also, the second control means produces the first
 control signal based on the synchronizing signal and outputs it from the
 seventh terminal to the image pickup apparatus via the cable.
 Additionally, the power supply means outputs a power supply voltage from
 the eighth terminal and supplies it to the image pickup apparatus via the
 cable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to a block diagram illustrating a first embodiment of the present
 invention shown in FIG. 1, there are shown a video camera 50, and an
 expansion board 51 used as an image processing apparatus attached to a
 personal computer. The expansion board 51 incorporates video and sound
 data from the video camera 50, performs data expansion and compression,
 and executes communication control. A united cable 52, which is a feature
 of the present invention, is used for connecting the video camera 50 and
 the expansion board 51. Male and female connectors 54 and 55 serve to
 couple the united cable 52 to the video camera 50 and the expansion board
 51; the female connectors, for example, are provided at the video camera
 50 and the expansion board 51, while the male connectors are disposed at
 both ends of the cable 52. In FIG. 1, there are also shown a headset 53
 having a microphone 53a and earphones (speaker) 53b, and a headset cable
 56 for connecting the headset 53 to the video camera 50.
 FIG. 2 illustrates the connecting portions of the above-described connector
 54 or 55, and in this embodiment, an 8-pin mini DIN connector is used as
 the connector 54 or 55. In FIG. 2, there are shown terminal pins 1 through
 8 and an external shield 9 provided for the mini DIN connector.
 FIG. 3 is a schematic view illustrating contents of the united cable 52.
 The cable 52 has a core 11 of, for example, a 75.OMEGA.-coaxial cable
 line, an external conductor 12 of the coaxial cable, a core 13 and an
 external conductor 14 of another 75.OMEGA.-coaxial cable line, a signal
 line 15 using, for example, stranded wire, signal lines 16 through 18
 which are similar to the line 15, and an external shield 19.
 FIG. 4 is a block diagram illustrating the internal construction of the
 video camera 50. The video camera 50 has a charge-coupled device (CCD) 21
 serving as an image pickup device, an analog-to-digital (A/D) converter
 22, a camera processing circuit 23 used as signal processing means, an
 adder 24, a 75.OMEGA.-drive circuit 25, a 75.OMEGA.-resistor 26, a
 capacitor 27, a capacitor 28 for grounding AC components, a
 75.OMEGA.-drive circuit 29, a 75.OMEGA.-resistor 30, a capacitor 31, and a
 capacitor 32 for grounding AC components.
 The video camera 50 further includes a CCD-driving timing generator 33, a
 microcomputer 34, a processing circuit (Vertical Interval Data Signal,
 hereinafter referred to as "VIDS") 35 for transmitting and receiving data
 only during a vertical blanking interval for video images, a microphone
 input terminal 36 provided for the video camera 50, an microphone
 amplifier 37, a speaker output terminal 38 for the video camera 50, and a
 drive circuit 39. Reference numerals 1 through 9 shown in FIG. 4
 correspond to those shown in FIG. 2.
 FIG. 5 is a block diagram illustrating the internal configuration of the
 personal-computer expansion board 51 according to the present invention.
 The expansion board 51 has a first DC power supply circuit 61 for
 supplying power to the video camera 50, a second DC power supply circuit
 62 similar to the circuit 61, a capacitor 63, a capacitor 64 for grounding
 AC components, a 75.OMEGA.-terminating resistor 65, a video amplifier 66,
 an A/D converter 67, and a video processing circuit 68 serving as image
 processing means for compressing video data.
 The expansion board 51 further includes a capacitor 69, a capacitor 70 for
 grounding AC components, a 75.OMEGA.-terminating resistor 71, a video
 amplifier 72, an A/D converter 73, a processing circuit (VIDS) 74 for
 receiving and transmitting data only during a vertical blanking interval
 for video images, a microcomputer 75, a synchronizing signal generator 76,
 an audio A/D converter 77, an audio processing circuit 78 for expanding
 and compressing audio data, and an audio D/A converter 79. Reference
 numerals 1 through 9 shown in FIG. 5 are associated with those illustrated
 in FIG. 2.
 The operation of the first embodiment constructed as described above in
 accordance with the present invention will now be described with reference
 to FIGS. 1 through 5.
 The cover of a predetermined personal computer (not shown) is first opened
 to insert the expansion board 51 of the present invention into an
 expansion slot (not shown). The cover is then closed to mate the mini DIN
 connector (for example, the male type of the connector shown in FIG. 2)
 provided at one end of the united cable 52 of the present invention and
 the mini DIN connector (for example, the female type of the connector
 shown in FIG. 2) disposed on the expansion board 51.
 Subsequently, the video camera 50 of the present invention is installed,
 for example, adjacent the monitor (not shown) of the personal computer,
 and the mini DIN connector (for example, the female type of the connector
 illustrated in FIG. 2) provided for the video camera 50 is mated with the
 mini DIN connector (for example, the male type of the connector shown in
 FIG. 2) provided at the other end of the united cable 52. Further, the
 headset 53 is connected to the headset input terminals 36 and 38 (FIG. 4)
 disposed at the video camera 50. Thus, the connection of the elements of
 the system shown in FIG. 1 is completed.
 Thereafter, power is supplied to the personal computer, and a predetermined
 software program is installed and run. Then, the expansion board 51 is
 initialized by the host CPU of the personal computer. Namely, the video
 processing circuit 68, the microcomputer 75, and the audio processing
 circuit 78 shown in FIG. 5 are initialized via the respective bus
 interfaces. In this manner, the microcomputer 75 for the expansion board
 51 is ready for receiving commands from the host CPU of the personal
 computer.
 In this condition, the user commands the start of a videoconference by a
 predetermined operation so as to cause the host CPU to send the
 microcomputer 75 a predetermined command to switch on the power supply to
 the video camera 50. In response to this command, the microcomputer 75
 transmits a signal indicating an instruction to turn the video camera on
 to the power supply circuits 61 and 62, thereby outputting a predetermined
 DC voltage to the terminal pins 2 and 4, respectively, of the 8-pin mini
 DIN connector (FIG. 2). The DC voltage is further output to the external
 conductors 12 and 14 (FIG. 3) of the coaxial cable lines of the united
 cable 52 via the above terminal pins 2 and 4, respectively. The external
 conductors 12 and 14 are capable of supplying a DC voltage by virtue of
 the capacitors 64 and 70.
 The DC voltage reaches the video camera 50 via the united cable 52 and is
 applied to the terminal pins 2 and 4 (FIG. 4) of the video camera 50 via
 the 8-pin mini DIN connector (FIG. 2). In this video camera 50, as well as
 in the expansion board 51, the external conductors 12 and 14 of the
 coaxial cable lines are able to supply a DC voltage by the aid of the
 capacitors 28 and 32 (FIG. 4), thereby making it possible to utilize the
 DC voltage to power the video camera 50.
 According to the above description, DC power is fed to the internal circuit
 (FIG. 4) of the video camera 50 so as to start the operation. In the above
 explanation, two DC power supply circuits are simultaneously turned on.
 The power supply circuits may be, however, sequentially switched on, which
 is effective for specific cases, such as providing a power-saving wait
 mode (switching off some of the power sources to enhance power
 conservation during standby) for the video camera 50.
 The video camera 50 is then switched on. Upon completion of the
 initialization of the microcomputer 34 (FIG. 4) provided for the video
 camera 50, the microcomputer 75 (FIG. 5) for the expansion board 51
 controls the VIDS processing circuit 74 to cause it to send a
 predetermined command to the terminal pin 5 (FIG. 5). This command is sent
 only during the vertical blanking interval in order to prevent the entry
 of noise into video images. The command reaches the terminal pin 5 (FIG.
 4) disposed at the video camera 50 via the signal line 15 (FIG. 3) of the
 united cable 52 and is input into the VIDS processing circuit 35 (FIG. 4)
 for the video camera 50. The command is further decoded and sent to the
 microcomputer 34, thereby causing the microcomputer 34 to perform a
 predetermined corresponding operation.
 For returning a response command, the microcomputer 34 controls its VIDS
 processing circuit 35 to cause it to transmit a predetermined response
 command to the adder 24 (FIG. 4). In the adder 24, the command is
 superimposed on an analog luminance signal output from the camera
 processing circuit 23 during the vertical blanking interval, and the
 superimposed signal is transmitted to the terminal pin 1 via the
 75.OMEGA.-drive circuit 25, the 75.OMEGA.-resistor 26, and the capacitor
 27.
 The response command superimposed on the luminance signal (only during the
 vertical blanking interval) reaches the terminal pin 1 (FIG. 5) provided
 at the expansion board 51 via the core 11 (FIG. 3) of the coaxial cable
 line of the united cable 52. The above luminance signal is further
 transmitted to the A/D converter 67 in which the signal is converted into
 digital data via the capacitor 63 and the video amplifier 66.
 The above response command, which is contained during the vertical blanking
 interval of the digital data, is decoded by the VIDS processing circuit 74
 and is sent to the microcomputer 75 for the expansion board 51. The
 microcomputer 75 receives the response command and transmits it to the
 host CPU of the personal computer via the bus interface. Then, the CPU can
 ascertain that the video camera 50 has been switched on and positively
 starts the operation.
 In the above-described communication control, for achieving noise
 reduction, it is important to match the two-way vertical blanking
 intervals between the video camera 50 and the expansion board 51. To meet
 this requirement, a composite synchronizing signal (C.SYNC) from the
 synchronizing signal generator 76 (FIG. 5) should be supplied to the
 terminal pin 6 (FIG. 4) of the video camera 50 from the terminal pin 6 of
 the expansion board 51 via the signal line 16 (FIG. 3) of the united cable
 52 the moment the signal (C.SYNC) is supplied to the VIDS processing
 circuit 74.
 Thus, the composite synchronizing signal (C.SYNC) is also transmitted to
 the VIDS processing circuit 35, the CCD-driving timing generator 33, and
 the camera processing circuit 23 provided for the video camera 50.
 Therefore, the two-way vertical blanking intervals are synchronized, i.e.,
 the two-way intervals containing the control data are matched.
 Once the video camera 50 is switched on and the two-way communication
 control is established between the video camera 50 and the expansion board
 51, various camera control operations, such as pan and tilt control for
 the pan-tilt mechanism (not shown), and an iris control for the camera,
 can be achieved by an operation similar to the aforedescribed operation.
 An explanation will now be given of the operation of the video system.
 A video signal from the CCD 21 (FIG. 4) is converted into digital data by
 the A/D converter 22 and is fed to the camera processing circuit 23
 serving as signal processing means. In the camera processing circuit 23,
 predetermined color processing and white balance control are performed on
 the data, for example, in a digital manner. The data is then converted
 into an analog signal by a built-in D/A converter, and is output as a
 luminance signal Y and a chrominance signal C. The luminance signal Y is
 sent to the adder 24 in which control data from the VIDS processing
 circuit 35 is superimposed on the luminance signal Y during the vertical
 blanking interval.
 The luminance signal Y superimposed by the control data is then output from
 the terminal pin 1 via the 75.OMEGA.-drive circuit 25, the
 75.OMEGA.-resistor 26, and the capacitor 27. The return signal from the
 above superimposed luminance signal Y returns to a GND of the
 75.OMEGA.-drive circuit 25 from the terminal pin 2 via the capacitor 28.
 The "go" and "return" components of the signal form a pair with respect to
 alternating currents of the superimposed luminance signal Y, and the
 AC-component pair is transmitted in the core 11 and the external conductor
 12 (FIG. 3) of the 75.OMEGA.-coaxial cable line of the united cable 52.
 The AC-component pair of the superimposed luminance signal reaches the
 terminal pins 1 and 2 of the expansion board 51 via the united cable 52,
 and are further supplied to the input terminal and the GND of the video
 amplifier 66 via the capacitors 63 and 64, respectively. The luminance
 signal Y correctly transmitted with 75.OMEGA. is amplified by the video
 amplifier 66 to a predetermined magnitude, and is then converted into
 digital data by the A/D converter 67. The digital data is then sent to the
 video processing circuit 68 serving as image processing means in which the
 image data is compressed to small-capacity data. The data is then
 transmitted to the host CPU via the bus interface.
 Meanwhile, the chrominance signal C output from the camera processing
 circuit 23 (FIG. 4) of the video camera 50 is processed in a manner
 similar to the luminance signal Y, except that control data is not
 superimposed on the chrominance signal C during the vertical blanking
 interval. More specifically, the signal C is transmitted to the video
 processing circuit 68 serving as image processing means of the expansion
 board 51 via the capacitors 69 and 70, the amplifier 72, and the A/D
 converter 73, and is compressed in the processing circuit 68.
 The operation of the sound system will now be explained.
 A microphone output signal from the headset 53 is fed to the microphone
 amplifier 37 of the video camera 50 via the microphone input terminal 36.
 The output of the microphone amplifier 37 is then transmitted via the
 terminal pin 7 and reaches the terminal pin 7 (FIG. 5) of the expansion
 board 51 via the signal line 17 (FIG. 3) of the united cable 52. This
 sound signal is converted into digital data by the A/D converter 77. The
 digital data is then sent to the audio processing circuit 78 and is
 compressed in a predetermined manner to small-capacity data. The
 compressed data is then transmitted to the host CPU via the bus interface.
 In contrast, sound data transmitted from a distal end through the
 videoconference system and received from the host CPU via the bus
 interface is expanded by the audio processing circuit 78 and is output to
 the D/A converter 79. The expanded data is then reconverted into an analog
 audio signal in the D/A converter 79 and is output to the terminal pin 8.
 The data reaches the terminal pin 8 (FIG. 4) of the video camera 50 via
 the signal line 18 (FIG. 3) of the united cable 52. After the sound signal
 is amplified by the speaker-driving amplifier 39 to a predetermined
 magnitude, it is transmitted to the headset 53 via the terminal 38 and is
 reproduced by the speakers (headphones) in the headset 53.
 As discussed above, in this embodiment only a single cable is used for
 connecting the video camera 50 and the expansion board 51, and DC power
 and all the signals, such as video signals, control signals, and sound
 signals, are allowed to pass through this cable. Thus, the major wiring
 for interconnecting the video camera 50 and the expansion board 51 of the
 desktop videoconference system requires only one cable. In this
 embodiment, this cable is referred to as "the united cable 52", and mini
 DIN connectors are cost-effectively used for the united cable 52, and more
 particularly, 8-pin mini DIN connectors are used because 4 and 8-pin mini
 DIN connectors are the least expensive and most commonly used among 3, 4,
 5, 6, 7, 8-pin mini DIN connectors. It should be noted that cost reduction
 can be achieved because 4-pin mini DIN connectors are employed in an S
 video cable, and 8-pin mini DIN connectors are used for RS232C connectors.
 The united cable 52 using the above-described 8-pin mini DIN connectors is
 constructed in the following manner.
 (1) Two coaxial cable lines are respectively used to allow the passage of
 two types of video signals, i.e., luminance signals Y and chrominance
 signals C, through the cores of the coaxial cable lines. The external
 conductors of the coaxial cable lines are used in such a manner that AC
 components are grounded.
 (2) DC power is supplied to the external conductors of the coaxial cable
 lines, and the external shield 19 is used as a GND for the DC power
 supply.
 (3) The control signals include three types of signals, i.e., synchronous
 clock, Rx, and Tx, based on synchronous serial transmission. Among these
 signals, Tx signals transmitted from the video camera 50 are multiplexed
 during the vertical blanking interval of the above-described video
 signals, for example, the luminance signals Y. The remaining synchronous
 clock and Rx signals to be output to the video camera 50 pass through two
 signal lines. The external shield 19 of the united cable 52 is used as a
 GND for the two signals.
 (4) Two signal lines are used for sound signals, for example, microphone
 signals and speaker signals. The external shield 19 of the united cable 52
 is employed as a GND for these signals.
 In summary, 6 pins formed of two coaxial cable lines and two signal lines
 are allocated to DC power, video signals and the control system, while 2
 pins are used for the sound system; in total, 8 pins are required to
 attain the whole system, and 8-pin mini DIN connectors are thus usable for
 the united cable 52.
 FIG. 6 is a block diagram of the video camera 50 according to a second
 embodiment of the present invention. FIG. 7 is a block diagram
 illustrating the expansion board 51 of the second embodiment.
 The second embodiment differs from the first embodiment in the following
 points. An output signal of the CCD 21 (FIG. 6) is directly used in place
 of the luminance signal Y, and control data is superimposed on the output
 signal during the vertical blanking interval. Further, instead of using
 the chrominance signal C, a "CCD-signal sampling clock" output from the
 timing generator 33 (FIG. 6) is used.
 More specifically, referring to the block diagram of the video camera 50
 shown in FIG. 6, the output signal from the CCD 21 is transmitted to the
 adder 24 in which the control data is superimposed on the signal during
 the vertical blanking interval. On the other hand, the CCD-signal sampling
 clock from the timing generator 33 is sent to the 75.OMEGA.-drive circuit
 29. The CCD signal is then transmitted to the A/D converter 67 of the
 expansion board 51 shown in FIG. 7 via the united cable 52. Meanwhile, the
 sampling clock (CCDCLK) is transmitted to the A/D converter 67 via the
 video amplifier 72. The output digital data from the A/D converter 67 is
 then sent to the camera processing circuit 23 in which predetermined color
 processing and white balance control are performed in a digital manner.
 Namely, the second embodiment can be greatly differentiated from the first
 embodiment in that camera processing, i.e., signal processing, is executed
 in the expansion board 51, and not in the video camera 50 as in the first
 embodiment.
 FIG. 8 is a block diagram illustrating the sound system of the video camera
 50 according to a third embodiment of the present invention. The third
 embodiment is different from the first and second embodiments in that the
 speaker-driving amplifier 39 (FIGS. 4 and 6) within the video camera 50 is
 replaced by a microphone amplifier 91 (FIG. 8) to implement a stereo
 system.
 The connecting state of the third embodiment is shown in FIG. 9. The use of
 the headset 53 shown in FIG. 1 is traded off for implementing a microphone
 stereo system.
 According to the aforedescribed embodiments, the following advantages can
 be presented.
 (1) All of the power supply cable, the control data cable, the video cable,
 and the sound cable are integrated so that only one cable is required to
 connect the video camera 50 and the expansion board 51, thereby improving
 reliability and external appearance from an aesthetic point of view.
 (2) For performing camera control, there is no need to use an RS232C
 terminal of a personal computer, and the RS232C terminal can be
 accordingly allocated to another device, such as a modem or a printer.
 (3) An AC adapter can be eliminated since power to the video camera 50 can
 be supplied from the expansion board 51. Thus, system cost can be reduced,
 and there is no possibility of forgetting to switch the video camera 50
 on, thereby enhancing ease of operation.
 (4) The headset 53 is connected not to the expansion board 51 but to the
 video camera 50. Accordingly, the headset 53 is easy to attach, and when
 not in use, easy to disconnect from the video camera 50 and accommodate.
 (5) In the second embodiment, camera processing, i.e., signal processing,
 can be executed by the expansion board 51. This makes it possible to
 reduce the size of the video camera 50 and also requires only one video
 A/D converter (three in the first embodiment), thereby reducing the cost.
 As is seen from the foregoing description, the present invention offers the
 following advantages.
 According to an embodiment of the present invention, power-supply voltages,
 control signals, sound signals, and video signals can be transmitted
 through only one cable, thereby improving reliability and external
 appearance from an aesthetic point of view.
 According to an embodiment of the present invention, since there is no need
 to use an RS232C terminal of a personal computer in order to receive
 control signals, the RS232C terminal can be allocated to other devices.
 Moreover, an AC adapter for receiving the power supply is not required.
 This reduces cost and eliminates the possibility of forgetting to switch
 the power on, thereby enhancing ease of operation.
 Further, first and second terminals for inputting and outputting sound
 signals and processing means, such as amplifying means, are provided for
 the image pickup apparatus. This makes it possible to connect the headset
 to the image pickup apparatus, thereby enhancing ease of operation.
 Additionally, signal processing means may be disposed in the image
 processing apparatus, thereby downsizing the image pickup apparatus.
 While the present invention has been described with reference to what are
 presently considered to be the preferred embodiments, it is to be
 understood that the invention is not limited to the disclosed embodiments.
 To the contrary, the invention is intended to cover various modifications
 and equivalent arrangements included within the spirit and scope of the
 appended claims. The scope of the following claims is to be accorded the
 broadest interpretation so as to encompass all such modifications and
 equivalent structures and functions.