JP4706464B2 - Video transmission system - Google Patents

Description

  The present invention relates to a video transmission system including one or more terminal devices that transmit a video signal via a signal line, and a main device that receives the video signal transmitted from the terminal device and displays a video. .

2. Description of the Related Art Conventionally, there has been provided a video transmission system that transmits a video signal from a terminal device connected to a signal line and receives the video signal by a main device that is also connected to the signal line (see, for example, Patent Document 1). In such a conventional example, a plurality of terminal devices connected to the signal line adopt a time division multiplex transmission system in order to transmit a video signal without collision. That is, collisions can be prevented by allowing each terminal device to store and transmit video signals in different time slots. Here, since the video signal transmitted through the signal line has a very large amount of data, a modulation method with a fast symbol rate is adopted, or the number of bits (multilevel) represented by one symbol is large. A modulation scheme must be adopted.
JP 2001-285235 A

  By the way, in the time division multiplex transmission method, a synchronization signal is required for recognizing a common time slot in each terminal apparatus, but usually the synchronization signal and the video signal are modulated and transmitted by the same modulation method. However, as described above, if the synchronization signal is modulated by a modulation method with a fast symbol rate or a modulation method with a large multilevel, it is difficult to reliably transmit the synchronization signal when the attenuation amount of the transmission line (signal line) is large. Thus, a transmission error is likely to occur.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a video transmission system capable of reliably transmitting a synchronization signal and preventing transmission errors.

  In order to achieve the above object, the first aspect of the present invention provides one or more terminal devices that transmit a video signal through a signal line, and a main device that displays a video by receiving a video signal transmitted from the terminal device. A video transmission system in which the main device identifies each terminal device by a unique identification code given to each terminal device, the terminal device capturing an image captured by the imaging unit and the imaging unit Modulating means for modulating, demodulating means for demodulating a synchronization signal fetched from a signal line, and storing the video signal modulated by the modulating means in a time slot set based on the demodulated synchronization signal and time-division multiplex transmission The main unit has a receiving unit for receiving a video signal transmitted via a signal line, a demodulating unit for demodulating the video signal received by the receiving unit, and stores them in the same number of time slots. The Compared to the video signal modulation method, the video restoration means for restoring the original video by connecting the video demodulated by the demodulation means for each video signal, the display means for displaying the restored video, Synchronization signal transmitting means for transmitting a synchronization signal modulated by a high modulation method to each terminal device via a signal line.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the main device has a plurality of power supply means for supplying power to the terminal devices connected to the signal line through signal lines of different systems. To do.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the synchronization signal transmitting means includes, in the synchronization signal, the allocation information of the terminal apparatus for the plurality of time slots and the transmission propriety information by the time slots. The transmission means determines a time slot for transmitting the video signal based on the allocation information, and transmits the video signal using the time slot when transmission is permitted by the transmission enable / disable information.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the main device and the terminal device are connected via a signal line, and a video signal transmitted from the terminal device is received and displayed. Or a plurality of display devices, the display device receiving means for receiving a video signal transmitted via a signal line, demodulating means for demodulating the video signal received by the receiving means, and an identification code included in the video signal And a video restoring means for restoring the original video by connecting the video demodulated by the demodulating means for each video signal having the same video signal, and a display means for displaying the restored video.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the invention, the terminal device is always connected to the signal line and has a higher impedance than the line impedance of the signal line, and the synchronization signal passes through the first terminal. It has a path and a second path that is connected to the signal line only when the video signal is transmitted and through which the video signal passes.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the terminal device includes an amplifying unit that is inserted into the second path and amplifies the video signal, and a second path before the video signal is transmitted from the transmission unit. And a path connection means for connecting to the signal line.

  A seventh aspect of the invention is characterized in that, in the sixth aspect of the invention, the path connecting means is capable of adjusting the timing of connecting the second path to the signal line.

  The invention of claim 8 is characterized in that, in any one of the inventions of claims 1 to 7, the transmission means stops transmission of the video signal when the synchronization signal cannot be received one or more times.

  According to a ninth aspect of the invention, in the third aspect of the invention, the transmission means transmits or stops the video signal based on a plurality of synchronization signals including the same information.

  According to the first aspect of the present invention, the synchronization signal is modulated by the modulation method having a higher attenuation tolerance than the modulation method of the video signal in the main apparatus. Thus, the synchronization signal can be reliably transmitted to prevent transmission errors.

  According to the invention of claim 2, even if the identification code of the terminal device connected to the signal line of one system and the identification code of the terminal device connected to the signal line of another system overlap, both signal lines As long as power is not supplied at the same time, it is possible to individually recognize terminal devices with overlapping identification codes, and it is also possible to incorporate terminal devices with fixed identification codes into the system.

  According to the invention of claim 3, since the synchronization information includes the allocation information of the terminal device for a plurality of time slots and the transmission availability information by the time slot, the designation of the terminal device that transmits the video signal and the transmission Whether or not it is possible can be independently indicated, so that the control in the main apparatus becomes simple and the amount of information to be confirmed by the terminal apparatus can be reduced.

  According to the invention of claim 4, since it is not necessary to transmit a synchronizing signal from the main device to the display device, the degree of freedom of the wiring form of the signal lines is increased.

  According to the invention of claim 5, the synchronization signal can be received by the first route in all the terminal devices, and only the terminal device that transmits the video signal is connected to the signal line by the second route. More terminal devices can be connected to the signal line while suppressing signal attenuation.

  According to the invention of claim 6, since the second path is connected to the signal line before the video signal is transmitted from the transmission means, the video signal is amplified when the amplifying means for amplifying the video signal is in an unstable operation state. Can be prevented from being transmitted, and transmission quality and transmission reliability are improved.

  According to the seventh aspect of the present invention, since the timing for connecting the second path to the signal line can be adjusted by the path connecting means, the optimum timing for connecting the second path to the signal line varies depending on various factors. Even if you can.

  According to the invention of claim 8, since the synchronization signal cannot be received, it is possible to prevent a malfunction such as storing and transmitting the video signal in the wrong time slot in the terminal device.

  According to the ninth aspect of the invention, since the transmission means transmits or stops the video signal based on a plurality of synchronization signals including the same information, malfunction due to the influence of noise can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the video transmission system of the present embodiment has a plurality of terminal devices 2 ₁₁ , 2 ₁₂ , 2 ₁₃ ... 2 ₂₁ , 2 ₂₂ , 2 that transmit video signals via signal lines L 1, L 2. _23, ... and, via a terminal device _{2 1i, 2 2j (i,} j = 1,2,3, ...) signal line a video signal division multiplex transmission time from L1, L2 and transmits the synchronization signal SY A main apparatus 1 that receives and displays video, and a display apparatus 3 that receives the video signal time-division multiplexed from the terminal apparatuses 2 _1i and 2 _2j via the main apparatus 1 via the signal line L3 and displays the video. ₁ , 3 ₂ , 3 ₃ ,... Here, a balanced line such as a pair line is used for the signal lines L1, L2, and L3, but an unbalanced line such as a coaxial line may be used. Further, a pair of enhanced category 5 or category 6 LAN cables or a pair of CPEV cables may be used for the signal lines L1, L2, and L3.

As shown in FIG. 1, the terminal device ₂₁₃ includes an imaging unit 20 having an optical system such as an individual imaging device and a lens, a signal processing unit 21 that amplifies the output of the imaging unit 20 and converts it into a digital signal, and signal processing Modulator / demodulator 22 that modulates the digital video signal (video data) output from unit 21 and demodulates synchronization signal SY, and transmits the video signal modulated by modulator / demodulator 22 and receives synchronization signal SY. A transmission / reception unit 23, a microphone 24a and a speaker 24b, a voice processing unit 24c having a two-wire / four-wire conversion function and a voice switch function, a control unit 25 that controls each unit using a CPU as a main component, and a main device 1 A control signal transmission / reception unit 26 that transmits and receives control signals via the signal line L1, and an audio signal output from the audio processing unit 24c and a video output from the transmission / reception unit 23 And a control signal output from the control signal transmission / reception unit 26 are frequency-division-multiplexed and a demultiplexing unit 27 that separates a voice signal and a control signal transmitted from the main apparatus 1 through the signal line L1, and an internal power supply from a commercial AC power source. And a power supply circuit 28 for generating an operating power supply (direct current).

  The transmission / reception unit 23 includes a first path in which a series circuit of the resistor element R and the amplifier A1 is inserted, and a second path in which a series circuit of the switch SW and the amplifier A2 that is on / off controlled by the control unit 25 is inserted. And have. The first path is always connected to the signal line L1 via the demultiplexing unit 27, and the resistance value of the resistance element R is set to a value larger than the line impedance of the signal line L1. The second path is connected to the signal line L1 via the demultiplexing unit 27 only when the switch SW is turned on by the control unit 25. The amplifier A2 is also turned on / off by the control unit 25.

Here, the terminal devices 2 _1i and 2 _2j have not only the imaging function as described above but also a model (for example, the terminal device 2 ₁₃ ) having a call function and having a unique power source (power supply circuit 28), and illustration is omitted. However, there is a mixture of models (for example, terminal devices 2 ₁₁ and 2 ₂₁ ) that have only an imaging function and are fed with power from the main device 1 via the signal lines L1 and L2 without having an original power source. Yes. Further, in principle, a unique identification code is _assigned to the terminal devices 2 _1i and 2 _2j , and the main device 1 identifies each of the terminal devices 2 _1i and 2 _2j by this identification code.

The main device 1 supplies two power supplies to a control unit 10 having a CPU as a main component and terminal devices (2 ₁₁ , 2 ₂₁ ) that do not have their own power source by superimposing DC power on each of the signal lines L1, L2. Power feeding units 11a and 11b, microphone 12a and speaker 12b, audio processing unit 12c having a two-wire / four-line conversion function and an audio switch function, transmission / reception for transmitting a synchronization signal SY, receiving a video signal, and transmitting / receiving a control signal 13, a modulation / demodulation unit 14 that modulates the synchronization signal SY output from the signal processing unit 15 and demodulates the video signal received by the transmission / reception unit 13, and a video that generates the synchronization signal SY and is demodulated by the modulation / demodulation unit 14 A signal processing unit 15 that reconstructs the original video from the signal (video data) and a video that is composed of a display device such as an LCD panel and is reconstructed by the signal processing unit 15 are displayed. The display unit 16, the audio signal output from the audio processing unit 12 c, the synchronization signal SY output from the transmission / reception unit 13, and the control signal output from the control unit 10 are frequency-division multiplexed and connected to the terminal via the signal lines L 1 and L 2. A demultiplexing / branching unit 17 that separates video signals, control signals, and audio signals transmitted from the devices 2 ₁₁ ,... And branches the video signals to the signal line L3, and an internal operating power supply (DC) from a commercial AC power supply Power supply circuit 18.

The synchronization signal SY is composed of a header part and a data part as shown in FIG. The header part includes a preamble, a packet type, a modulation method, a time slot transmission availability code Ax, Bx, Cx, Dx, a data length, and an error correction code. Here, transmission permission / inhibition codes Ax, Bx, Cx, and Dx indicate whether or not video signals can be transmitted to the four time slots A, B, C, and D defined in this system from the main apparatus 1 to the terminal apparatuses 2 _1i , 2 _2j. To notify. On the other hand, the data part is composed of allocation information Ay, By, Cy, Dy and error correction codes of the terminal devices 2 _1i , 2 _2j for the time slots A, B, C, D. In the allocation information Ay, By, Cy, Dy, the identification codes of the terminal devices 2 _1i , 2 _2j are respectively stored by the main device 1, and the terminal devices 2 of the identification codes stored in the allocation information Ay, By, Cy, Dy, respectively. _1i and 2 _2j transmit video signals using time slots A, B, C and D, respectively. However, even if identification codes are stored in the allocation information Ay, By, Cy, Dy, only the time slots A, B, C, D permitted by the transmission permission / inhibition codes Ax, Bx, Cx, Dx can be used. Needless to say.

As shown in FIG. 2B, the video signal is also composed of a header part and a data part. It is desirable that the header part is modulated by a modulation method having a better attenuation resistance than the data part. The header part includes a preamble, an identification code indicating the transmission source terminal devices 2 _1i and 2 _2j , a packet type, a modulation method, a video data line number, a data length, and an error correction code. On the other hand, the data part is composed of video data and an error correction code. Here, the video data is video data for each line as shown in FIG. 3, and one frame of video is reconstructed by connecting the video data for each line in the vertical direction in the order of video data line numbers. (A so-called progressive method is adopted).

In the main device 1 and the terminal devices 2 _1i and 2 _2j , as shown in FIG. 4, the time when a predetermined waiting time T has elapsed from the falling edge of the synchronization signal SY is set as the start time of the first time slot A, and the next synchronization is performed. Four time slots A, B, C, and D are arranged within a period until the signal SY rises (signal transmission period). Here, in this embodiment, since four time slots A, B, C, and D are arranged within the signal transmission period, a maximum of four terminal devices 2 _1i and 2 _2j can individually transmit video signals. The standby time T and the intervals between the time slots A, B, C, and D are the time t1 required for switching between transmission and reception in the main device 1 and the terminal devices 2 _1i and 2 _2j , and the main device 1 and the main device 1. Must be longer than the sum of the time t2 that is twice the transmission delay time to the terminal devices 2 _1i and 2 _2j farthest from the terminal device 2 and the maximum error time t3 of the operation clock of the terminal devices 2 _1i and 2 _2j (t1 + t2 + t3 <T).

By the way, moving image data generally has a very large amount of data, but if you try to transmit it in a limited transmission band, you have to slow down the symbol rate (in general, if the amount of transmitted data is large, you need to increase the symbol rate). However, if the symbol rate is increased, the transmission path becomes broadband transmission), modulation schemes such as multi-level modulation schemes (modulation schemes with a large multi-level degree) and multi-carrier modulation schemes (modulation schemes with low symbol rates) Must be used. On the other hand, in such a modulation method with a low symbol rate or a modulation method with a large multilevel, the rate of occurrence of transmission errors increases when the attenuation amount of the transmission path (signal lines L1, L2) is large. When a transmission error occurs in the video signal, the phenomenon that the video is not displayed at all can be avoided by omitting the video data of the line that could not be retransmitted or received and displaying the video. In other words, if the attenuation characteristic of the header portion of the video signal is high, an error is unlikely to occur in the line number. On the other hand, if a transmission error occurs in the synchronization signal SY, the video signals cannot be displayed because the video signals cannot be transmitted from the terminal devices 2 _1i and 2 _2j .

  Therefore, in the present embodiment, for the video signal, a modulation method with a slow symbol rate or a modulation method with a large multilevel (for example, QPSK <Quadrature Phase Shift Keying> or QAM <Quadrature Amplitude Modulation>) is used, and the synchronization signal SY is used. Uses a modulation method (for example, BPSK <Binary Phase Shift Keying>) having a fast symbol rate or a low multi-level, that is, high attenuation resistance compared to the video signal modulation method. The modulation / demodulation units 14 and 22 of the apparatus 2 switch the modulation / demodulation method between the synchronization signal SY and the video signal.

  Thus, as described above, since the main apparatus 1 modulates the synchronization signal SY by a modulation method having a higher attenuation resistance than the video signal modulation method, the main device 1 uses a modulation method having a low symbol rate as well as a video signal. As compared with the case where modulation is performed with a modulation method having a large value, the synchronization signal SY can be reliably transmitted to prevent transmission errors.

Next, the operation of the present embodiment will be described by taking as an example a case where a video image captured by the terminal device 2 ₁₃ is displayed on the main device 1 at the same time as a call is made between the main device 1 and the terminal device 2 ₁₃ .

First, call button provided to the control signal transmission unit 26 generates and a call notification to the control unit 25 (not shown) is operated calls main device 1, the control signal transmission unit 26 in the terminal apparatus 2 ₁₃ The call notification and its own identification code are sent to the signal line L1 via the demultiplexing unit 27 by the control signal. Further, the control unit 25 activates the imaging unit 20 to image a person who operates the call button, converts the captured image into a digital signal by the signal processing unit 21, and converts the converted image data to a frame memory (not shown). accumulate.

On the other hand, in the main apparatus 1, the control unit 10 that has received the control signal via the signal line L1 causes the ringing sound from the speaker 12b and activates the transmission / reception unit 13, the modem unit 14, and the signal processing unit 15 to activate the signal processing unit. The modulation signal demodulating unit 14 modulates the synchronization signal SY generated by the signal 15 and transmits the signal to the signal line L1 from the transmitting / receiving unit 13 via the demultiplexing / branching unit 17. At this time, in the synchronization signal SY generated by the signal processing unit 15, for example, the transmission permission code Ax of the first time slot A is permitted to be transmitted, and the allocation information Ay of the first time slot A is further added to the call source terminal device 2 _13. Are stored.

In the terminal device ₂₁₃ is taken into the modem unit 22 the synchronization signal SY separated by the demultiplexer 27 passes through the first path of the transceiver 23 is sent to the control unit 25 is demodulated by the modem part 22 . When the control unit 25 confirms that the transmission permission / rejection code Ax is permitted to be transmitted and the identification information is stored in the allocation information Ay, the modulation / demodulation unit 22 modulates the video data stored in the frame memory. Generate a video signal. When the video signal is ready for transmission, the control unit 25 activates the amplifier A2 of the transmission / reception unit 23 and turns on the switch SW to amplify the video signal generated by the modulation / demodulation unit 22 with the amplifier A2, and through the switch SW. The signal is transmitted from the demultiplexing unit 27 to the main apparatus 1 via the signal line L1.

In the main apparatus 1, the video signal transmitted via the signal line L 1 is separated by the demultiplexing / branching unit 17 and received by the transmitting / receiving unit 13, and the video data demodulated by the modem unit 14 is input to the signal processing unit 15. The signal processing unit 15 reconstructs one frame of video by sequentially connecting the video data received based on the video data line number included in the header of the video signal in the vertical direction, and outputs it to the display unit 16 to output the video. Display. Then, when another person who has viewed the video on the display unit 16 operates a response button (not shown) of the main device 1, the control unit 10 activates the voice processing unit 12b to enable a call, and further transmits a control signal as a signal. by sending to the line L1 and notifies the call start to the caller of the terminal device 2 _13.

Control unit 25 of the terminal apparatus ₂₁₃ which has received the control signal of the call start notification may enable a call to start audio processing section 24c, is collected by the microphone 24a video signal the audio signal output from the audio processing unit 24c Are multiplexed (frequency division multiplexed) and transmitted to the main apparatus 1 through the signal line L1, and the demultiplexing unit 27 converts the synchronization signal SY and the audio signal transmitted from the main apparatus 1 through the signal line L1. The voice signal is input to the voice processing unit 24c, and the call voice is generated from the speaker 24b.

When the main device 1 or the terminal device operation call end at 2 ₁₃ is, the allocation information Ay emptied with a not transmit the transmission capability code Ax of the main in the device 1 synchronizing signal SY, the terminal device 2 ₁₃ The control unit 25 turns off the switch SW of the transmission / reception unit 23 to stop the transmission of the video signal.

Further, when transmitting a video signal from the no terminal device 2 ₂₁ calls functions as well as its own power supply, the terminal by the control unit 10 to superimpose a DC power to the signal line L2 Start feeding portion 11b in the main device 1 The apparatus ₂₂₁ is activated, the transmission / reception unit 13 and the modulation / demodulation unit 14 are activated, the synchronization signal SY generated by the signal processing unit 15 is modulated by the modulation / demodulation unit 14, and the signal line is transmitted from the transmission / reception unit 13 through the demultiplexing / branching unit 17. Send to L2. At this time, in the synchronization signal SY generated by the signal processing unit 15, for example, the transmission permission code Ax of the first time slot A is permitted to be transmitted, and the terminal device 2 that is the transmission source in the allocation information Ay of the first time slot A ₂₁ identification codes are stored. Here, the terminal device ₂₁₁ of the same type that are connected to the other signal line L1 (the call function and no model of the own power supply), the source connected to the signal line L2 terminal 2 ₂₁ Can be given the same identification code. That is, in the main apparatus 1, only one of the two signal lines L1 and L2 is alternatively supplied with power from the power supply unit 11a or 11b, so that the two terminal apparatuses 2 ₁₁ and 2 ₂₁ having the same identification code are simultaneously connected. Since it does not start up, both of these two terminal devices 2 ₁₁ and 2 ₂₁ can normally transmit the video signal to the main device 1, and as a result, an identification code such as a dip switch is set. It is possible to incorporate a terminal device that does not have a means for performing identification and has a fixed identification code into the system.

On the other hand, the terminal device 2 _21, transmission availability code Ax is the transmission permission, and the own identification code in allocation information Ay to ensure that it is stored, and stores the video signal in the transmission permission time slot A The signal is transmitted to the main device 1 through the signal line L2. Then, until the synchronization signal SY which the allocation information Ay emptied with a not transmit the transmission availability code Ax is transmitted from the main unit 1, continued transmission of the video signal terminals 2 ₂₁ by the time slot A which is assigned To do.

By the way, in the main device 1, the video signals transmitted from the terminal devices 2 _1i and 2 _2j are branched to the signal line L3 by the demultiplexing / branching unit 17, and the display devices 3 ₁ and 3 ₂ connected to the signal line L3. , 3 ₃ , as with the main device 1, the images captured by the terminal devices 2 _1i , 2 _2j can be displayed on a display device such as an LCD. Here, in the display device 3 _k (k = 1, 2, 3), the transmission source terminal devices 2 _1i and 2 _2j are identified by the identification code included in the header portion of the video signal, and the identification codes are the same. The original video can be restored (reconstructed) by connecting the demodulated video data for each video signal. Therefore, since the display device 3 _k does not need the synchronization signal SY, there is no need to transmit the synchronization signal SY from the main device 1 to the signal line L3, and there is an advantage that the degree of freedom of the wiring form of the signal line L3 is increased. In particular, when only the display device 3 _k is connected to the signal line L3 as in the illustrated example, a signal is transmitted only in one direction from the main device 1 to the display device 3 _k . Can only be in one direction.

Further, in the present embodiment, whether or not transmission is possible using the allocation information Ay, By, Cy, Dy and the time slots A, B, C, D of the terminal devices 2 _1i , 2 _2j for a plurality of time slots A, B, C, D (Transmitability code) Since Ax, Bx, Cx, and Dx are included in the synchronization signal SY, the designation of the terminal devices 2 _1i and 2 _2j that transmit the video signal and whether or not to transmit can be independently indicated. There is an advantage that the control in the main device 1 becomes simple and the amount of information to be confirmed by the terminal devices 2 _1i and 2 _2j can be reduced. Here, if the transmission availability information (transmission availability code) Ax, Bx, Cx, Dx has a 1-bit configuration, the amount of data can be particularly reduced, so that the operation load on the terminal devices 2 _1i , 2 _2j can be further reduced. Furthermore, the synchronization signal SY can be received by the first path of the transmission / reception unit 23 in all the terminal devices 2 _1i , 2 _2j , and only the terminal device 2 _1i , 2 _2j that transmits the video signal is the second of the transmission / reception unit 23. Since there is only one terminal device 2 _1i , 2 _2j connected to the signal lines L 1, L 2 at the same time because it is connected to the signal lines L 1, L 2 through the path of, more terminals can be suppressed by suppressing the attenuation of the video signal. The devices 2 _1i and 2 _2j can be connected to the signal lines L1 and L2. In the first path, since the resistance value of the resistance element R is set to a value larger than the line impedance of the signal lines L1 and L2, the attenuation amount of the synchronization signal SY increases. In the embodiment, since the synchronization signal SY is modulated by a modulation method having high attenuation tolerance, the generation of transmission errors can be suppressed and the synchronization signals SY can be reliably received by the terminal devices 2 _1i and 2 _2j . Further, in the terminal devices 2 _1i and 2 _2j , before the video signal is output from the modem unit 22, the control unit 25 turns on the switch SW and connects the second path to the signal lines L 1 and L 2. There is an advantage that the video signal can be prevented from being transmitted when the amplifier A2 to be amplified is in an unstable operation state, and transmission quality and transmission reliability are improved. Here, in the terminal devices 2 _1i and 2 _2j , the control unit 25 can adjust the timing at which the switch SW is switched from OFF to ON, and it is optimal to connect the second path to the signal lines L1 and L2 due to various factors. Even if the timing changes, it can respond. However, as a method of giving a timing adjustment instruction to the control unit 25, a method of operating operation means (volume or the like) prepared in the terminal devices 2 _1i and 2 _2j , or the control unit 10 detects a transmission error. It is possible to adjust automatically.

By the way, when the terminal device 2 _1i , 2 _2j transmitting the video signal cannot receive the synchronization signal SY transmitted from the main device 1 due to some failure, the control unit 25 of the terminal device 2 _1i , 2 _2j. Then, since the transmission of the video signal is stopped unless the synchronization signal SY is continuously received a plurality of times (for example, three times), the synchronization signal cannot be received, so that the terminal devices 2 _1i and 2 _2j enter an incorrect time slot. A malfunction such as storing and transmitting a video signal can be prevented. Further, when the synchronization information SY obtained by changing the allocation information Ay, By, Cy, Dy and the transmission permission / rejection codes Ax, Bx, Cx, Dx is transmitted, the control unit 25 of the terminal devices 2 _1i , 2 _2j has the same information. Only when a synchronization signal SY including (assignment information and transmission permission code) is continuously received a plurality of times (for example, three times), processing corresponding to the information (transmission or stoppage of the video signal) is performed. For example, it is possible to prevent malfunctions due to the influence of noise, for example, the case where a plurality of terminal devices 2 _1i and 2 _2j store video signals in the same time slot. Note that, instead of the condition that the synchronization signal SY having the same content is received three times continuously as described above, the condition that the synchronization signal SY having the same content is received three times among the five consecutive synchronization signals SY. When the above condition is satisfied, the control unit 25 may execute processing according to the information and allow a transmission error of the synchronization signal SY up to two times out of five times.

  Here, as shown in FIG. 5, by simply connecting the connector of the functional module 108 to the connection port of the gate device 103, the power path and the information path of the functional module 108 can be secured at the same time. There is a wiring system that can be connected also to the gate device 103 and is excellent in workability. In this wiring system, one or a plurality of switch boxes 102 embedded and disposed at appropriate positions in a building are provided, and a power line 110 and an information line 111 that are wired in advance in a wall surface between the switch boxes 102 are sent and wired. At the same time, the switch box 102 at the beginning is drawn into the wiring board 101 and led indoors through the main breaker MB and the branch breaker BB, and the power line 110 is introduced, and the gateway 120 is connected to the external Internet network NT. An information line 111 connected via a router and a built-in hub is introduced. It is also possible to incorporate the video transmission system according to the present invention in such a wiring system. More specifically, the main device 1 according to the present invention is connected to the gate device 103 as the functional module 108, and the model that requires commercial power supply among the terminal devices 2 according to the present invention is also referred to as the functional module 108. The terminal device 2 according to the present invention may be connected to a different gate device 103, and a model that does not require commercial power supply is connected to the power line 110 and the information line 111 without being connected to the power line 110 and the information line 111. It is only necessary to connect the local wiring as shown in FIG.

It is a system configuration figure showing an embodiment of the present invention. (A) is an explanatory view of the synchronization signal in the above, and (b) is an explanatory view of the video signal in the above. It is explanatory drawing of the video data in the same as the above. It is a time chart of a synchronous signal and a time slot in the same as the above. It is a system configuration diagram of a wiring system incorporating the same.

Explanation of symbols

1 Main device 2 _{11 to} 2 ₁₃ , 2 ₂₁ to 2 ₂₃ Terminal device 3 _{1 to} 3 ₃ Display device SY Sync signal L1 to L3 Signal line

Claims (9)

A unique identification given to each terminal device, comprising one or more terminal devices that transmit a video signal via a signal line, and a main device that receives the video signal transmitted from the terminal device and displays the video A video transmission system in which a main device identifies each terminal device by a code,
The terminal device includes: an imaging unit; a modulating unit that modulates an image captured by the imaging unit; a demodulating unit that demodulates a synchronization signal captured from a signal line; and a modulation unit that modulates a time slot set based on the demodulated synchronization signal Transmission means for storing the video signal modulated in step multiplex transmission and time division multiplex transmission,
The main apparatus has a receiving means for receiving a video signal transmitted via a signal line, a demodulating means for demodulating the video signal received by the receiving means, and each video signal stored in the same number of time slots. A video restoration unit that restores the original video by connecting the video demodulated by the demodulation unit, a display unit that displays the restored video, and a modulation method that has higher attenuation resistance than the modulation method of the video signal. A video transmission system comprising synchronization signal transmission means for transmitting a synchronization signal to each terminal device via a signal line.   The video transmission system according to claim 1, wherein the main device includes a plurality of power supply units that supply power to the terminal devices connected to the signal lines through signal lines of different systems. The synchronization signal transmitting means includes, in the synchronization signal, allocation information of terminal devices for a plurality of time slots and whether or not transmission by the time slots is possible,
3. The transmission means determines a time slot for transmitting a video signal based on the allocation information, and transmits the video signal using the time slot when transmission is permitted by the transmission enable / disable information. Video transmission system. Comprising one or more display devices that are connected to the main device and the terminal device via a signal line, receive a video signal transmitted from the terminal device, and display a video;
The display device includes: a receiving unit that receives a video signal transmitted through a signal line; a demodulating unit that demodulates the video signal received by the receiving unit; and a video signal having the same identification code included in the video signal. The video restoration means for connecting the videos demodulated by the demodulation means to restore the original video, and the display means for displaying the restored video. Video transmission system.   The terminal device is always connected to the signal line, has a higher impedance than the line impedance of the signal line, and passes through the synchronization signal. The terminal device is connected to the signal line only when the video signal is transmitted, and the video signal passes. The video transmission system according to claim 1, further comprising a second path.   The terminal device includes amplification means that is inserted into the second path and amplifies the video signal, and path connection means that connects the second path to the signal line before the video signal is transmitted from the transmission means. The video transmission system according to claim 5, wherein:   7. The video transmission system according to claim 6, wherein the path connecting means is capable of adjusting a timing for connecting the second path to the signal line.   8. The video transmission system according to claim 1, wherein the transmission means stops transmission of the video signal when the synchronization signal cannot be received one or more times.   4. The video transmission system according to claim 3, wherein the transmission means transmits or stops the video signal based on a plurality of synchronization signals including the same information.

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