JPS63220632A - Information transmission equipment - Google Patents

Abstract

PURPOSE:To efficiently attain biderectional transmission with simple constitution by detecting the traffic of call on a line, when the traffic of call is a prescribed quantity or above, controlling the sending condition of a random access transmitting signal from a terminal device, and executing the above-mentioned transmitting in a prescribed condition. CONSTITUTION:By a call traffic detecting circuit 46, the traffic of call of a random access transmitting line is detected, supplied to a main control device 8, the call traffic comes to a constant quantity or above, then, a prescribe bit in CADA data is used from the device 8 through a CADA encoder 6, and a call traffic increasing signal is supplied to respective terminal devices 30. When the signal is supplied to a CADA decoder 36 of the terminal devices 30, the transmitting conditions of a transmitting signal are changed by respective terminal devices. For the present example, the packet length of the transmitting packet which is the transmitting signal is shortened. Thus, the call traffic is decreased and the collision of the transmitting signal is reduced.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Essentials of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Example G1 Description of transmitting side G2 Explanation on terminal side G3 Explanation of polling transmission 04 Explanation of random access transmission The present invention relates to an information transmission device suitable for use in transmitting information signals and the like from a terminal device side as well as transmitting information signals and the like from a terminal device side.

B. Summary of the Invention The present invention transmits information signals, etc. from a central control unit to a terminal device provided for each passenger seat of, for example, an airplane, nine trains, or a bus, and also transmits information signals, etc. from the terminal device side. In an information transmission device capable of two-way communication suitable for use in means is provided, and when the traffic volume detection means detects a traffic volume of a predetermined amount or more, the transmission state of the random access transmission signal from each terminal device is controlled so that the random access transmission is performed in a predetermined state. By doing so, information can be transmitted efficiently.

C. Prior Art For example, U.S. Pat. No. 4,584,603 teaches providing separate video displays for passenger seats in vehicles such as aircraft. That is, video displays are individually provided in passenger seats, a plurality of video signals are transmitted in parallel to these video displays, and each video display selects and displays one of the signals.

D. Problems to be Solved by the Invention In this conventional device, multiple video signals are transmitted to each video display using independent transmission lines, and many transmission lines are required. It is.

Therefore, there is a problem that the wiring becomes complicated and the device becomes complicated.

In particular, if two-way communication is possible by transmitting information such as seat status from each video display to a control device that supplies video signals, more transmission lines will be required and the configuration will require more transmission lines. had become more complicated. In addition, aircraft have tended to become larger in recent years, for example, 500
It was nearly impossible to do this kind of wiring on an aircraft that had more than just seats.

In view of the above, an object of the present invention is to provide an information transmission device that has a simple configuration and is capable of efficient bidirectional transmission.

E. Means for Solving the Problems The information transmission device of the present invention includes, for example, a central control device (8) and a plurality of terminal devices (30), as shown in FIG.

(30)... are connected for two-way communication, and transmission from the plurality of terminal devices (30), (30)... to the central control unit (8) is performed using a predetermined line. In an information transmission device that performs random access transmission,
Call N detection means (46) of the line is provided, and when this call volume detection means (46) detects a call volume of more than a predetermined amount, each terminal bag f& (30), (30)... The transmission state of the random access transmission signal is controlled so that random access transmission is performed in a predetermined state.

F. Effect: According to the information transmission device of the present invention, when the traffic volume of the random access transmission line increases, the transmission state of the random access transmission signal from each terminal device (30) is controlled, thereby increasing transmission success. Control can be performed according to setting conditions, such as preventing a drop in transmission rate and preventing an increase in transmission time, so that information can be transmitted efficiently.

G. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. This example is a video signal inside an aircraft.

This is a transmission device that transmits audio signals, etc.

Description of the G1 transmitting side First, the transmitting side as a central control device will be explained with reference to FIG. In FIG. 1, (1a) to (1d) are video tape recorders installed on the transmission side, such as in a crew cabin. The videotape recorder (1a) is for override use, and is loaded with a cassette tape in which information on how to put on a life jacket, etc. is recorded. Further, video tape recorders (1b) to (1d) are loaded with cassette tapes on which movies are recorded. These videotape recorders (
1a) to (1d) include a terminal (2) to which a reproduced video signal is output, and a terminal (R) to which a reproduced audio signal is output.

A is provided. These video tape recorders (1
a) to (1d) are compatible with two languages, terminals R and R are output terminals for the left audio signal and right audio signal in the language of the first country, respectively, and terminal A is the output terminal for the left audio signal and right audio signal in the language of the second country, respectively. This is an output terminal for monaural audio signals.

Further, (2) is a television tuner, and this television tuner (2) is provided with a terminal V to which a video signal is output, and a terminal R to which an audio signal is output. Terminals R and R are output terminals for the left audio signal and right audio signal, respectively.

In addition, (3) is a still image playback device, which plays compact discs, so-called CDs, on which maps, airport guide maps, etc. are recorded.
It is designed to play ROM. This still image reproducing device (3) is provided with a terminal (2) to which a still image video signal is output, and a terminal A to which an audio signal is output.

Further, (4a) and (4b) are audio playback machines each comprising three compact disc players (CD players) and three tape recorders;
) and (4b) are provided with six pairs of terminals R to which audio signals are output, respectively.

Terminals R and R are output terminals for the left audio signal and right audio signal, respectively.

Further, (5) is a control device, (5a) is a microphone, (5b) is a volume that adjusts the level of the audio signal from the microphone (5a), (5C) is an announce key, (5d) is an override key, (5e)～
(5g) are video tape recorders (1b) to (1d), respectively.
) is a pause key to put the cursor into a pause state. Video signals obtained at terminals V and audio signals obtained at terminals R and A of the video tape recorders (1a) and (1b) are respectively supplied to a control device (5). The control device (5) is provided with a video signal output terminal ■ and an audio signal output terminal R, A, and these output terminals V
A video tape recorder (1b
), the video signal obtained from terminal ■ and the audio signal obtained from terminals R and A are output, but the override key (
When pressing 5d) to turn on the override, the video signal obtained at terminal V and the audio signal obtained at terminals R and A of the video tape recorder (1a) are output. Also, when pressing the announce key (5c) to turn on the announcement, connect the microphone (5a) to output terminal A.
The audio signal from is output.

Further, (6) and (7) are CADA encoders used in a conventionally well-known cable digital audio/data transmission system (CAD eight system).

A CADA system, for example, time-division multiplexes multiple digital audio signals and transmits them as CADA data using the band of one free CATV TV channel (6 MIIz).
This is an extremely efficient transmission system.

The CAD encoders (6) and (7) are configured with an A/D converter and a shift register, and convert a plurality of audio signals into digital signals with the A/D converter, and then output the signals to predetermined positions of the shift register, respectively. It is configured to perform time division multiplexing by inputting signals in parallel and outputting them serially at high speed from this shift register. Note that not only digital audio but also control data and data for computer software can be multiplexed.

Output terminal of the control device (5) mentioned above, R
.

The audio signal obtained at A is supplied to an encoder (6). In addition, the audio signals obtained from the output terminals of the video tape recorder (IC) and (1d), R and A are output to the encoder (
6). Furthermore, the audio signals obtained at the output terminals R of the tuner (2) and the output terminal A of the still image player (3) are supplied to an encoder (6).

In addition, the audio signal obtained at R is transmitted through the 6 pairs of output terminals of the audio player (4a), the 3 pairs of output terminals of the R and audio player (4b), and the audio signal obtained at R. It is supplied to encoders (6) and (7).

In addition, the override key of the control device (5)
(5d), Announce key (5c), Bose key (
When keys 5e) to 5g are pressed, the control device (5) generates control data SC1 corresponding to the pressed key, and this control data SC1 is supplied to the encoder (6).

The encoder (6) is provided with output terminals A to E from which pause control signals are output in accordance with the control data SC1, and the pause control signals obtained at these output terminals A to E cause the respective video tape recorders (1b )～(1d
), the audio players (4a) and (4b) are controlled. That is, the override key (5d) and the announce key (5d)
When C) is pressed, a pause control signal is output to the output terminals A-E, and the video tape recorders (1b> to (l)
d) The audio players (4a) and (4b) are all in a pause state. Furthermore, when pause keys (5e) to (5g) are pressed, pause control signals are output to output terminals A to C, respectively, and video tape recorders (Ib) to (1d
) are each put into a pause state.

Further, (8) is a master controller consisting of a computer that performs in-flight management, and this master controller (8) generates control data SC2 that controls the terminal device on the receiving side.
C2 is supplied to the encoder (6).

This control data SC2 is, for example, data requesting data indicating the state of the seat where the terminal device is installed.

In addition, (9a) is a ROM in which menu data is written.
, (9b) to (9h) are ROMs in which different game data is written. This ROM (9a) to (9h)
Computer software data S read out from
O is supplied to a signal processing circuit (10), where an error correction code is added, etc., and then supplied to an encoder (7).

The control data SCI and SC2 are also supplied from the encoder (6) to the encoder (7).

Further, at the output terminal 0 of the encoder (6), a signal 5CA1 obtained by time-division multiplexing of the digitally converted plurality of supplied audio signals and the control data SCt and SC2 is obtained, and this signal 5CA1 is sent to the modulator. (llf
) and AM modulated using the VSB (vestigial sideband) method. Further, at the output terminal 0 of the encoder (7), a signal S which is a time-division multiplexed signal of digitally converted signals of the plurality of supplied audio signals, control data SCs, SC2, and computer software data Sol is provided.
cΔ2 is obtained, and this signal 5CA2 is sent to the modulator (l1g)
and is AM modulated using the VSB method.

Furthermore, the video signal obtained at the output terminal (■) of the control device (5) is supplied to the modulator (lla), and the audio signal obtained at the output terminal A of the control device (5) is supplied to the modulator (lla). be done. Modulator (Ila)
After the audio signal is FM modulated and frequency multiplexed with the video signal to make it similar to a normal television signal,
AM modulated using the VSB method.

Also, video tape recorder (LC), (Id)
.

Tuner (2) and still image player (3) output terminal■
The video signals obtained are transmitted through modulators (llb) to (li
e) and is AM modulated using the VSB method.

Here, the modulators (1, 1a) to (Ilg) are configured to sequentially modulate frequency bands every two channels to prevent cross-modulation, for example, on 60 or more television broadcast channels.

Further, the output signals of the modulators (lla) to (l1g) are supplied to an adder (12) and frequency-multiplexed. and,
The frequency-multiplexed signal SMF from the adder (12) is supplied via a duplexer (13) to one end of a leaky cable (21) constituting a bidirectional signal transmission means. The other end of this leaky cable (21) is connected to a terminating resistor (22) for termination. This leaky cable (21) is, for example, a coaxial cable with a spiral cutout around it to increase the amount of signal leakage.

In addition, signals supplied to the central control unit via the key cables (21) from each terminal device (3o), which will be described later, are supplied to the demodulator (43) via the duplexer (13). Ru. The signals supplied from each terminal device (30) include a polling transmission signal and a random access transmission signal, as will be described later. ). The demodulation supply (43) demodulates the polling transmission signal and the random access transmission signal, which are modulated and supplied for transmission, and supplies them to the CADA encoder (6). Further, the random access transmission signal demodulated by the demodulator (43) is supplied to the detector (44). This detector (44) envelope-detects the supplied random access transmission signal and outputs it, and supplies the output signal of this detector (44) to the master controller (8). By supplying the detection signal to the master controller (8) in this manner, the master controller I/roller (8) can detect whether there is random access transmission from any terminal device (30).

Further, the output signal of the wave detector (44) is supplied to the traffic detection circuit (46) via the integrating circuit (45). The traffic detection circuit (46) is a circuit that detects the level of the detection signal integrated and averaged by the integration circuit (45), and supplies this level detection signal to the master controller (8).

By supplying the level detection signal to the master controller (8) in this manner, the amount of random access transmission from each terminal device (30) can be detected by the master controller (8).

Description of the G2 Terminal Side Further, (30) is a terminal device provided individually in the passenger seat of the aircraft, and only one terminal device is shown in FIG. In this terminal device (30), (31) is a leaky key
- This is an antenna for capturing the frequency multiplexed signal SMF leaking from the pull (21). The frequency multiplexed signal SMF captured by this antenna (31) is passed through a splitter (32) to a TV tuner (33) and a CADA tuner (3).
4). The tuner (33) is connected to the modulator (1, 1
, a) to (11, e), and the tuner (34) can selectively receive channels in the output frequency bands of the modulators (llf) and (Ilg). It is configured as follows,
Channel selection in these tuners (33) and (34) is controlled by a selection display device (35).

Further, the video signal and the audio signal outputted from the tuner (33) are supplied to the selection display device (35), and the time division multiplexed signal 5CA1 outputted from the tuner (34).
Alternatively, 5CA2 is supplied to the CADA decoder (36). This CADA decoder (36) is a selection display device (
35) CA supplied in response to each key operation described below
Time division multiplexed signal Sc8 or 5C which is DA data
Desired data is extracted from A2, and the extracted data is supplied to the selection table G water device (35) or personal computer (37).

Further, FIG. 2 shows an example of the configuration of the panel surface of the selection display device (35), and this panel surface is arranged on the back of the passenger seat as shown in FIG. 3.

In Fig. 2, (35a) is a display device consisting of a flat cathode ray tube, liquid crystal display, etc., (35b) is an audio output terminal to which headphones (35c) are connected, and (35d) is an audio output terminal to which headphones (35c) are connected.
is a game terminal to which a joystick (35e) or the like (see FIG. 1) for games is connected.

Also, (35f) is the TV selection key, (35g > is the music selection key, (35h) is the channel display, (35g) is the music selection key, (35h) is the channel display,
5i) is a channel down key, and (35j) is a channel up key. In this case, use the TV selection key (3
5f) and press the channel down key (35j)
, channel up key (35j) in sequence, the television channels can be changed in sequence. That is, the reception channel in the TV tuner (33) and the audio signal output from the CADA decoder (36) are changed, and the display device (35a) displays the video tape recorder (1b).
~(ld), the tuner (2), and the screen of the video signal output from the still image player (3) are sequentially displayed, and
A corresponding audio signal is output to the audio output terminal (35b). Here, when the audio signal is in two languages, two channels are assigned to one video signal screen, the first channel is the audio signal in the language of the first country, and the second channel is the audio signal in the language of the second country. An audio signal in this language is output. Also, by pressing the music selection key (35g), then pressing the channel down key (351) and channel up key (35j) in sequence, the music channel can be changed in sequence. That is, the audio signal output from the CADA decoder (36) is changed, and the audio signal output terminal (
35b) is an audio player (4a).

The audio signals output from (4b) are sequentially output.

Also, (35k) is the menu display key, (3!M) is the cursor down key, (35m) is the cursor up key,
(35n) is the enter key. In this case, by pressing the menu display key (35k), a video signal based on the data from the menu ROM (9a) is supplied from the personal computer (37) to the selection display device (35), and the menu is displayed on the display device (35a). The screen will be displayed. After selecting a game by moving the cursor on the display screen using the cursor down key (354) and cursor up key (35m), press the enter key (35n).
By pressing , the video and audio signals based on the data from the game ROMs (9b) to (9h) selected by the personal computer (37) are displayed on the selection display device (3).
5), the game screen is displayed on the display device (35a), and the game audio signal is outputted to the audio output terminal (35b).

Also, in Figure 2, (35p) is the stewardess call key, (35q) is the reading light key, and (35r) is the stewardess call key.
is a volume for adjusting the volume.

! , a frequency multiplexed signal SM containing control data SC2 sent from the master controller (8) to the leaky cable (21) via the CADA encoder (6).
F is captured by the antenna (31) of each terminal device (30) and supplied to the CADA tuner (34).

This CADA tuner (34) is a frequency multiplexed signal SM.
The above-mentioned signal 5CAI, which is CADA data, is received from F and supplied to the CADA decoder (36). This CADA decoder (36) is configured as shown in FIG.
When the signal ScΔ1 is supplied to the CADA data input terminal (36a), it is supplied to the decoder (36b) via the CADA data input terminal (36a). This decoding unit (36b) is a microcomputer (36c) included in the decoder (36).
C according to instructions from or included in the CADA data.
It demodulates necessary predetermined data from the ADA data and supplies it to the microcomputer (36c).

Further, the microcomputer (36c) is supplied with a selection signal from the selection display device (35) via the selection signal input terminal (36d) by operating each key, and is supplied with the selection signal included in the CADA data from the personal computer (37). A game data selection signal is sent to the microcomputer (36c) via a game selection signal input terminal (36e).
supplied to Also, a microcomputer (36c)
The demodulated audio and other various data signals are supplied to the selection display device (35) via the output terminal (36f), and the demodulated game data signals are supplied to the personal computer via the output terminal (36g). (37).

In addition, an address generator (36b) and a seat 10 storage section (36i) are incorporated in this CADA decoder (36), and the address generator (36b) outputs information about the seat (or seat) on which this terminal device (30) is attached. This terminal device (30
) is supplied to the microcomputer (36c), and from the seat ID storage unit (36i), the terminal device (30)
Information regarding the seat (or the seat on which the user of this terminal device (30) is seated), such as the manufacturing date and model, is supplied to the microcomputer (36c).

In addition, a sensor (39) for detecting the state of this seat is connected to a microcomputer (36c), and the sensor (39) detects the seatbelt fastening state and the operating state of the reclining mechanism of this seat. Supplied to the computer (36c).

From this CADA decoder (36), a predetermined signal can be transmitted to a master controller (8) of the central control unit via a transmitter (38). In this case, the transmitter (38) includes a random access transmitter (38a) and a polling transmitter (38b), as shown in FIG.
, (38b), after superimposing a carrier wave of a predetermined frequency on the transmission signal, both transmitting units (38a
), (38b) output signals are sent to the adder (38c)
and frequency multiplexed. In the case of this example, f 1 (
779,0Ml-1z) as the carrier wave, and in the case of hauling transmission, f2 (779,2M!(z)) as the carrier wave.Then, the signal frequency multiplexed by the adder (38c) is the output of the transmitter (38). A signal is supplied from the terminal (38d) to the antenna (31) via the duplexer (32), and the signal is transmitted from this antenna (31) to the central control unit via the leaky cable (21). The signal supplied from the terminal device (30) to the device side is separated from other signals by the demultiplexer (13), and then sent to the demodulator (43).
The transmission signal demodulated by this demodulator (43) is supplied to the CADA encoder (6), and this encoder (
6) supplies data based on the transmission signal from the terminal device (3) to the master controller (8).

Explanation of G3 polling transmission Next, polling transmission in which signals are supplied from each terminal device (30) to the central controller side under the control of the central controller side in the transmission device of this example will be explained.

In this example, this polling transmission is carried out by the master controller (8) on the central control unit side to each terminal device (3
0) and the seat condition. For example, assume that the master controller (8) wants to know whether the passengers in each seat are wearing their seat belts. At this time, the master controller (
8 to the CADA encoder (6) from all terminal devices (
30) is supplied with control data SC2 requesting a response regarding seatbelt fastening information. At this time, since it is not possible to request responses from all the terminal devices (30) at the same time, the master controller (8) sequentially designates the addresses of the respective terminal devices (30) and outputs the control data SC2. For example, there are 2 passengers on this plane.
Assuming that there are 50 passengers, the addresses of all the seats in which these 250 passengers are seated are specified in order, and the control data SC2 is output 250 times.

Cono control data SC2 is CADA encoder (
6), this control data SC2 is time-division multiplexed with other audio signals, etc., as described above, and the signal S
c^1, and the signal 5CA1 which is this CADA data
is connected to each terminal device (
30). This signal 5CAI is transmitted to the terminal device (3
0), the CAD of each terminal device (3o)
In the decoder (36), the microcomputer (36c) discriminates the control data SC2 in the CAD data demodulated by the decoder (36b).

As a result of this determination, if the address specified by the control data SC2 matches the address output by the address generator (36h) of this terminal device (30), the microcomputer (36h) of this terminal device (30)
36c) outputs the seat belt fastening information signal instructed by the control data SC2 to the polling transmitter (38b) of the transmitter (38).

Note that this seatbelt wearing information is obtained from the sensor (
39) to the microcomputer (36c). Then, the polling transmitter (38b
) modulates the above-mentioned transmission signal for polling transmission, and sends this transmission signal to the transmitter (38c) via an adder (38c).
38) to the output terminal (38d). Then, it is supplied from this output terminal (38d) to the leaky cable (21) via the duplexer (32) and antenna (31). This seatbelt fastening information signal is transmitted from the leaky cable (21) to the duplexer (13) and demodulator (43).
The signal is supplied to the CADA encoder (6) on the central control unit side via the CADA encoder (6), and from the CADA encoder (6) to the master controller (8). This master controller (
8), when the seat belt fastening information signal is supplied to the master controller (8), the address of another seat is specified and the master controller (
8) outputs control data SC2 that requests a response regarding seatbelt fastening information. In this way, the control data SC2 requesting a response with seatbelt fastening information is sequentially outputted to all the terminal devices (30).

Terminal device (30) that corresponds to all seats in this way
By having the master controller (8) reply with seatbelt fastening information from the car, this master controller (8)
) side, it is possible to determine which passengers are wearing seat belts and which are not. Note that the time from when the master controller (8) outputs a signal to when a response is received is very short, so even if there are 250 seats, for example, polling transmission to all terminal devices (30) can be performed in a short period of time. be able to. Further, in the above example, the information grasped by the master controller (8) is the seat belt wearing information, but in addition to this, for example, the operating state of the reclining mechanism of each seat detected by the sensor (39), the selection display device (35) ) on the display device (35a), the selection state of the meal menu made by the passenger by operating the cursor keys, etc. on the selection display device (35), and the purchase request for in-flight sales made similarly by operating the cursor keys, etc. Various information that can be detected by the microcomputer (36c), such as the selection status of items, can be collected and understood.

04 Description of Random Access Transmission Next, random access transmission in which signals are supplied from each terminal device (30) to the central control device side at any time in the transmission device of this example will be explained.

In this example, this random access transmission is performed when the stewardess call key (35p) and reading light key (35q>) of the selection display device (35) are operated. When the call key (35p) is pressed, the CAD^ decoder (36) is sent from the selection display device (35) to the input terminal (36d).
A steward desk call signal is supplied to the microcomputer (36c). When this stewardess call signal is supplied to the microcomputer (36c), this stewardess call signal and address generator (36c)
6h) is supplied to the random access transmitter (38a) of the transmitter (38). Then, the random access transmitter (38a) modulates the above-mentioned transmission signal for random access transmission, and sends this transmission signal to the output terminal (38d) of the transmitter (38) via the adder (38c). supply and,
The signal is supplied from this output terminal (38d) to the leaky cable (21) via the duplexer (32) and antenna (31). This call signal is transmitted through a leaky cable (21
) is supplied to the CADA encoder (6) on the central control unit side via the demultiplexer (13) and demodulator (43). Then, based on this signal, the CPU (not shown) in the CADA encoder (6) controls the switch box (40).
), and the stewardess call light (41) corresponding to the seat designated by the address signal is turned on. Also, when the reading light key (35q) of the selection display device (35) is pressed, the terminal device (30
) side, the reading light lighting signal and address signal are supplied as random access transmission signals to the CADA encoder (6) of the central control unit, and the CADA encoder (6) in the CADA encoder (6)
The switch box (40) is controlled by the PU, and the reading light (40) corresponding to the seat designated by the address signal is
2) is turned on.

In this way, the lighting of the stewardess call light (41) and reading light (42) is controlled by random access transmission, and in this example, this random access transmission is performed in the state shown in FIG.

That is, in this example, the random access transmission signals output from each terminal device (30) are as shown in FIG. 6A.
One data transmission is performed with a transmission packet P of 22.4 ms. At this time, the carrier sense signal (Fig. 6B
) is the low level signal “0”, the terminal device (30
) before transmitting, and when the high level signal is “1”, it changes to the low level signal “0” and then 4.4
Transmission starts after ms. This carrier sense signal is
CA from the master controller (8) on the central control unit side
A signal is supplied to each terminal device (30) using a predetermined bit in the above-mentioned CADA data via a DA encoder (6), and a detector (44) is supplied to the master controller (8). When the detection signal determines that the transmission packet is being transmitted, it outputs a high level signal "1", and when it determines that the transmission packet is not being transmitted, it outputs a low level signal "0". In this way, any terminal device (
When the transmission packet I-P sent from 30) is accurately transmitted to the CADA encoder (6) on the central control unit side, immediately after receiving this transmission packet P, the CADA encoder (6) sends A and CK as response signals. A signal (acknowledgement signal) is transmitted to each terminal device (30) using a predetermined bit in the above-mentioned CADA data, and this random access transmission is completed.

However, for example, when this transmission packet P is sent from multiple terminal devices (30) at the same time, the transmission packet P)
P#lrl+ Suddenly, data is not accurately transmitted to the CADA encoder (6) on the central control unit side. In this case, as shown in FIG. 6C, CA immediately after receiving the transmission packet P.
A NACK signal (negative acknowledgment signal) is transmitted as a response signal from the DA encoder (6) to each terminal device (30) using predetermined bits in the above-mentioned CADA data.

CADA of the terminal device (30) that sent the transmission packet P
When the decoder (36) receives this NACK signal, it attempts to send the transmission packet P again, that is, retransmit the data. At this time, if the signal is retransmitted immediately, it will again collide with the retransmitted signal from another terminal device (30). Therefore, the timing of retransmission is staggered for each terminal device (30).

In the case of this example, the timing for performing this retransmission is determined by a carrier sense signal (see Fig. 6B) supplied from the central controller side.
). As mentioned above, this carrier sense signal outputs a high level signal "1" when it is determined that the transmitted packetlet is being transmitted by random access transmission, and outputs a low level signal "1" when it is determined that the transmission packet is not being transmitted.
0", the carrier sense signal becomes a high level signal "1" for 22.4 ms by transmitting the above-mentioned 22.4 ms transmission packet P (FIG. 6A). This carrier sense signal is transmitted to each terminal. It is received by the device (30), but due to a delay due to transmission in the leaky cable (21), the transmission bucket) P is sent out (point a in Figure 6), and then the A level signal of the carrier sense signal becomes "1". There is a deviation of 2.On+s until a change in the signal is detected (point b in Figure 6). Then, after 22.4ms, the carrier sense signal changes to a low level signal "0" (point C in Figure 6). ), an ACK signal or NACK signal is obtained as CADA data until 4.411IS has elapsed, and this 4.4
ms has elapsed (point d in Figure 6), each terminal device (
30), and the retransmission possible range is defined as the point from which 4.4111 seconds have elapsed. And a plurality of terminal devices (30)
In order to prevent simultaneous retransmission from
134.4ms) is set, and the possible retransmission range for qRketoro is set as follows:
1, second retransmission section R2, . . ., sixth retransmission section R6. The terminal device (30) then randomly selects each of these retransmission sections R1 to R6. For example, in this example, if the terminal device (30) selects the second reproduction section R2, the terminal device (30) outputs the retransmission packet RP in this section R2 and receives a response signal. At this time, there is no collision with other random access transmission signals, and when the ACK signal is supplied from the central control unit as shown in FIG. 6C, the transmission has been correctly performed and the transmission ends.

Also at this time, the carrier sense signal changes for only 22.4 ms. Further, from the terminal device (30) that outputs another transmission signal that collided with the first transmission packet P, for example, the fifth
Assuming that a transmission packet (not shown) is retransmitted during retransmission section R5, the carrier sense signal changes with a delay of 2.0 ms from this fifth retransmission section R5.

Furthermore, when the retransmitted packet RP also collides with other transmitted packets and is not transmitted correctly, a NACK signal is obtained as a response signal, and the carrier sense signal changes to a low level signal "0" (02 in Fig. 6). 4.4m after
Six retransmission sections are set with the period after s (point d' in FIG. 6) as the beginning of the retransmission possible range, and retransmission is attempted in randomly selected sections within these six sections. In this way, retransmission is repeated z times until the transmission is successful, but in this example, if the ACK signal is not returned even after 6 retransmissions and the transmission is not successful, the retransmission is stopped. However, under normal usage conditions, it is extremely rare that the transmission is not successful even after repeating the retransmission six times.

By retransmitting the transmission signal in this way, multiple terminal devices (30) can simultaneously press the stewardess call key (
35p) or the reading light key (35q) is operated, such commands are transmitted.

However, for example, if the cabin lights are turned off on an airplane and the reading light key (35q) is operated on a large number of terminal devices (30) to turn on the reading lights at the same time, at this time, random access transmission is not possible. Collisions of signals (transmitted packets) increase, and the probability that retransmission will not be successful increases even after 6 retransmissions. If this happens, press the reading light key (3).
In many cases, the reading light does not turn on even if the passenger presses the reading light key (3) until it turns on.
5q), there is a high possibility that more transmission packets will be sent, the average number of retransmissions will increase, and collisions will increase.

In order to prevent this, in this example, the traffic volume detection circuit (46) on the central control unit side detects the traffic volume of the random access transmission line and supplies it to the master controller (8).
When it is detected that the call volume exceeds a certain level, the master controller (8) sends a CADA encoder (
6), a call volume increase signal is supplied to each terminal device (30) using a predetermined focus in the CADA data. Note that the traffic volume referred to here is (transmission packet length) x (number of packets).

When this traffic increase signal is supplied to the CADA decoder (36) of the terminal device (30), each terminal device changes the transmission conditions of the random access transmission signal. In this example, as the transmission condition to be changed, the packet length of the transmission packet, which is the random access transmission signal, is set to 22.
．． Shorten from 4ms to 12.4ms. By shortening the packet length in this way, the traffic volume is reduced accordingly, collisions of transmitted signals are reduced, and a decrease in the success rate of random access transmission can be prevented.

Examples of transmission states when the packet length is changed are shown in FIGS. 7, 8, and 9. Each of these figures shows the terminal equipment (30
) is shown logarithmically on the horizontal axis as the transmission frequency. That is, for example, a transmission frequency of 1.00 is 250
This indicates that random access transmission was performed by operating the key (35p) or (35q) 100 times per hour from each terminal device (30). In FIGS. 7 to 9, the case where the packet length is 22.4 ms is shown as β, and the case where the packet length is 12.4 ms is shown as S.

In FIG. 7, the vertical axis shows the transmission failure rate, that is, the rate at which the transmission was not successful and the reading lamp was not turned on even after 6 retransmissions. As shown in FIG. 7, when the packet length is 22.4 ms, the failure rate increases rapidly when the transmission frequency exceeds 200, and reaches a failure rate of 80% when the transmission frequency is 400.

For this reason, for example, when the traffic volume exceeds the transmission frequency of 100, the central controller side outputs a traffic volume increase signal to suppress the packet length to 12.4ms.
However, the failure rate can be reduced to about 7%. For this reason,
The rate at which commands are executed by random access transmission is improved.

In addition, in Figures 8 and 9, the vertical axis shows the average delay time and maximum delay time, that is, when the reading light or stewardess call light is turned on after operating the key (35p) or (35q) on each terminal device (30). It shows the average time and maximum time until retransmission, and as the number of retransmissions increases, the delay time increases accordingly. In terms of this delay time, the delay time can be kept low by changing the packet length from 22.4 ms to 12.4 ms with a call volume corresponding to a transmission frequency of 100. In particular, when looking at the maximum delay time, when the packet length is 22.4 ms, it can take as much as 0.7 seconds at a transmission frequency of 200, whereas when the packet length is 12.4 ms, even at a transmission frequency of 400, it can take as long as 0.7 seconds.
Within seconds.

Therefore, it is possible to prevent the response from being delayed due to this random access transmission.

As described above, according to the transmission device according to the present example, by shortening the packet length when the call volume increases, it is possible to prevent a deterioration in responsiveness and an increase in the failure rate when the call volume increases. In addition,
If the transmission packet length is shortened, the amount of information that can be transmitted also decreases, but sufficient transmission can be achieved when the transmission packet is used to control the lighting of a reading lamp or the like as in this example.

In the above embodiment, the packet length is shortened due to an increase in call volume, but other transmission conditions may be changed. For example, even if various transmission conditions (parameters) are changed, such as limiting the number of retransmissions to 6 times in the above example, or increasing the possible retransmission range to 6 transmission packets in the above example, responsiveness may deteriorate and failures may occur. It is possible to prevent an increase in success rate.

However, since the responsiveness and success rate are not improved in proportion, it is necessary to appropriately select the transmission conditions to be changed depending on the intended use of the transmission device. For example, changing the packet length as in the above example is suitable when the main purpose is to improve responsiveness.

Furthermore, in the above embodiment, the traffic volume is detected from the averaged signal after detecting the random access transmission signal, but a transmission frequency detection means is provided, and the transmission frequency detection means The call volume may be detected based on the number of transmissions counted.

Furthermore, although the present invention is applied to an information transmission device in an aircraft in the above-described embodiment, it can be similarly applied to an information transmission device in a vehicle such as a train or a bus, or in a theater or stadium. Further, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

H Effects of the Invention According to the information transmission device of the present invention, the transmission state of the random access transmission signal from each terminal device (30) is controlled when the call volume of the random access transmission line increases. Control can be performed according to setting conditions such as preventing a decrease in the transmission success rate and preventing an increase in transmission time, and there is an advantage that information can be transmitted efficiently.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the information transmission device of the present invention, and FIGS. 2, 3, 5, 6, 7, 8, and 9 are respectively FIG. 4 is a diagram for explaining the example shown in FIG. 4, and is a configuration diagram of the main part of the example shown in FIG. (1B) to (1d) are video tape recorders, (2) is a television tuner, (3) is a still image player, (4a) and (4b) are audio players, (5) is a control device,
(6) and (7) are CADA encoders, (8) is a master controller, (9a) to (9h) are ROM,
(Ila) to (l1g) are modulators, (12) is an adder, (13) and (32) are duplexers, (21) is a leaky cable, (30) is a terminal device, (31) is an antenna, (33) is a TV tuner, (34) is a CAD^
tuner, (35) is the selection display device, (35p) is the stewardess call key, (35q) is the reading light key, (3
6) is a CADA decoder, (36b) is a decoding section, (
36c) is a microcomputer, (38) is a transmitter,
(38a) is a random access transmitter, (38b) is a polling transmitter, (39) is a sensor, (43) is a demodulator, (44) is a detector, (45) is an integration circuit, and (46) is a traffic volume. This is a detection circuit. 1) Dan Yun Therapy

Claims (1)

[Claims] A central control device and a plurality of terminal devices are connected to enable bidirectional communication, and transmission from the plurality of terminal devices to the central control device is performed by random access transmission using a predetermined line. In the information transmission apparatus, a traffic volume detection means for the line is provided, and when the traffic volume detection means detects a traffic volume exceeding a predetermined amount, the transmission state of the random access transmission signal from each of the terminal devices is determined. An information transmission device characterized in that the random access transmission is controlled so that the random access transmission is performed in a predetermined state.