JPS595791A - Catv system - Google Patents

Abstract

PURPOSE:To quicken response to a request from a terminal device, by deciding on only terminal devices which are powered on among numbers of terminal devices as objectives of polling. CONSTITUTION:A center 100 and terminal devices 200 are connected mutually through a coaxial cable 300 and a two-wave distributor 400. Only terminal devices which are powered on among the terminal devices 200 are registered to the CATV center 100. The center 100 receives a signal indicating a request from a terminal device 200 at its head end 10 and also sends a control signal and a television signal meeting its requirements. If there is data to be sent from, for example, a terminal device 102 to the center 100, this data is stored in a computer 201 temporarily. When the polling of the center 100 is performed, the signal is supplied to the computer 201, which discriminates whether the polling is address to the computer 201 or not. When the terminal device 102 is placed in a polling state in some period, the stored data is sent to the center 100 in the following period and the center 100 regards the data as data from the terminal device 102 to perform prescribed processing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water directional CATV system for use in hotels, for example.

For example, in a hotel, each room has an interactive CAT
It is conceivable to prepare a V terminal device (television receiver) and provide the following services to guests.

(i) Viewing TV broadcasts You can watch regular TV broadcasts and CATV broadcasts.

(ii) BGM You can listen to regular FM broadcasts and records.

(iii) Screening of movies Broadcast movies, etc. using a VTR.

(iv) Reservation For example, the menu at the restaurant in the hotel will be displayed on the screen, so you can reserve the food you like along with your seat.

(v) Shopping When the guest makes an instruction using the switch, various products are displayed on the screen and can be purchased.

(vi) Information about movies, theaters, etc. Displays the cast and other information about the movie currently being shown on the screen.

(vi) Absence service When the guest is absent, messages such as visitors and phone calls are displayed on the screen.

(vii) Checkout Guests can check the details of their accommodation costs in their room.

(1x) Information In the event of a fire, etc., this will be notified to guests.

(x) Others Information on how to use this CATV system, etc.

In this case, items (i) and (iii) must be continuous images (hereinafter referred to as "one video") as in normal broadcasting, but items (iv) and (vi) to (x) must be still images. good. Regarding item (v), it is effective to combine moving images and still images.

By the way, in a typical hotel room, coaxial cables 5C-2V are wired in all rooms for receiving TV broadcasts. Therefore, it would be very convenient if the above-mentioned C A TV could be implemented using this existing coaxial cable.

However, the upper limit of the transmission band of this coaxial cable is 400M.
Hz, which corresponds to only about 67 channels (67#400/6) of the television band, and in reality, commands and data cannot be accessed between the terminal equipment in each room and the CATV center. Since channels for this purpose are also required, the total number of channels is about 50 to 60. With such a number of channels, the above (i) to (
The number of channels is insufficient to realize item x).

Therefore, by solving the following problems, the above-mentioned (i) to (
An interactive CATV system for hotels that enables item x) can be considered.

First, let's explain an example. Note that the following example is a case of a hotel CATV system in the United States, and the number of terminal devices is 1024. Further, a video signal and an audio signal in the state of a modulated signal in television broadcasting etc. will be referred to as a television signal.

In Figures 1 and 2, (100) is the CA within the hotel.
The TV sending center (200) indicates the terminal equipment installed in each room, and the center (100) and the terminal equipment (
200) means, for example, a 5C-2V coaxial cable (30
0) and a bidirectional distributor (400).

Then, at the center (100) (Fig. 1), 0
ω indicates a head end, through which a signal indicating a request from the terminal device (200) is received, and a control signal and a television signal satisfying the request are sent out.

Further, (11) indicates a receiving device for receiving general CATV broadcasting outside the hotel, and (12) indicates a receiving device for receiving general TV broadcasting, and these receiving devices (11)
, (12) is composed of, for example, an RF amplifier, and the received TV signal (multiple channels) is subjected to level adjustment etc., but demodulation etc. is not performed, and the TV signal of the channel at the time of reception is sent to the head end α. is supplied to.

Furthermore, (13) shows a receiving device for receiving FM broadcasting, and the FM signal received thereby is also supplied to the head end aθ (without being tuned).

Furthermore, (14) indicates a plurality of record players or cassette players, and the audio signals played by these are supplied to the head end 0ω, converted into an FM signal in the same format as FM broadcasting, and then sent to the cable (300). .

In addition, (15A) and (15B) indicate, for example, a plurality of U-standard videotape players, in which the player (15A) constantly plays back movies, etc. in item (iii), and the playback signal is supplied to the head end αφ. be done.

In addition, the player (15B) has an image (video image) related to shopping in item (V), and the controller (25B)
), and during reproduction, code signals related to the contents of the reproduction screen can also be reproduced from the auxiliary track of the tape. And this player (1
5B) is also supplied to the head end QO).

Further, (16A) and (16B) indicate, for example, a plurality of laser-type video disc players, and from the player (16A), as well as the player (15A'),
The movie or the like in item (iii) is then played back, and the playback signal is supplied to the head end aω. Also, the player (
16B) has an image in l frame units (or l field units) for terms (iv) to (x), etc., and this is controlled by the controller (26) so that it can be reproduced in frame units, and its The reproduction signal is supplied to the head end (101). At the time of reproduction, the reproduction position (frame) can be specified by an address signal.

Further, (17) indicates a plurality of sheet recorders, which record video signals from a video camera (18) frame by frame using, for example, a cassette-type rotating magnetic sheet, and are capable of playing back the video signals. The reproduced video signal is supplied to the head end 0ω. Note that the sheet recorder (17) is used to reproduce items (iv) to (vi), etc., and has an address like a video disc, and is controlled by the controller (27) in units of one frame. A video signal from the camera (18) is also supplied to the headend signal.

Further, (30) indicates a microcomputer of a multi-CPU system, and this computer (30) is connected to a head end 00) and controllers (25) to (27) to carry out various controls, such as a terminal device (
200) is processed in response to a request. The hotel's main computer (50) is also connected to the computer (30).

Furthermore, (41) is a CRT monitor, and (42) is a printer, by which the monitor results of the CAT, V system, etc. are displayed or printed.

Here, the signals accessed between the center (100) and the terminal device (200) are assigned frequencies as shown in FIG. 3, for example.

That is, the frequency band 10~30MH2 is the terminal device (
200) to the center (100), and the band 10~20MHz is a channel for signals indicating requests from the terminal device (200), as will be described later, and the band 20~30MHz is a channel for signals indicating requests from the terminal device (200). Equipment (20
This is a channel for maintenance and inspection of item 0).

In addition, the frequency band 54 to 402 MHz is centered (10
0) to the terminal device (200), of which the bands 54 to 88 MHz and 17
4~216MH2 is the band of television broadcasting for the trial court,
CAT received by receiving devices (11) and (12)
The TV signal of V and the current TV signal (multiple channels) are sent out as is within this band as described above.
There is ζ. Furthermore, the band 88 to 108 MHz is the band for FM broadcasting, and the FM broadcasting (multiple channels) received by the receiving device (13) is also sent out as is within this band. Furthermore, the FM signal from the player (14) is also sent out within this band.

Furthermore, the band 108~120MHz is centered (100MHz).
) is the band of the control signal sent to the terminal device (200). Then, the signals from devices (15A) to (18) are transmitted in the remaining band 120 in the headend QOI.
~174MHz and 216~402MHz, and TV broadcast bands (54~88MHz, 174~216MHz)
MHz) and sent to the cable (300).

That is, moving images such as movies played on the players (15A), (15B) and the video disc player (16Δ) are played using a specific channel among the remaining channels, for example, an empty channel in the television broadcasting band. It is sent out all the time. The still image of one frame played back by the video disc player (16B) and the sheet recorder (17) is also transmitted to a specific channel among the remaining channels, for example, a band of 120 to 174 MHz.
and 216-402 MHz channels (details will be described later).

On the other hand, in the terminal device (200) (Fig. 2), (20
1) shows a microcomputer, which controls the operation of this device (200) and also controls the center (10).
0) is accessed by control signals. moreover,
(211) is a bandpass filter for extracting downlink signals, and (212) is a bandpass filter for extracting uplink signals, which are connected to the distributor (400). In addition, (211) indicates a tuner device for television, which is controlled by a microcomputer (201), receives necessary ones from among the multiple channels of television signals sent, and outputs video and audio signals. demodulated. The video signal and audio signal are then supplied to switch circuits (223) and (224).

Furthermore, (225) indicates a memory device, which can record one frame of the video signal from the tuner device (221) using, for example, a rotating magnetic sheet, and can perform still playback, in which this is continuously and repeatedly played back. The reproduced video signal is supplied to a switch circuit (223).

Further, (222) indicates an FM tuner device, which is also controlled by the computer (201), receives the necessary FM signals from the multiple channels sent, and extracts the audio signal. The audio signal is supplied to a switch circuit (224).

And these switch circuits (223), (224
') is controlled by a computer (201).

Furthermore, (226) indicates a character generator,
This is controlled by a computer (201), and a video signal to be reproduced as characters, numbers, etc. is extracted, and this is sent to a switch circuit (223) in a synthesis circuit (227).
) is combined with the video signal from The video signal from this synthesis circuit (227) is supplied to the television receiver (240), and the audio signal from the switch circuit (224) is also supplied to the television receiver (240).

In addition, (202) shows a demodulation circuit, and (203) shows a modulation circuit. A control signal sent on the downlink is extracted from the demodulation circuit (202) and supplied to the computer (201), and the control signal sent from the demodulation circuit (202) is supplied to the computer (201). ), the computer (201
) is modulated into the uplink band and passed through the filter (
212) to the cable (300).

Further, (231) indicates a transmitting unit of, for example, an infrared remote control, and (232) indicates its receiving device. The transmitting unit (231) has various switches, for example as shown in FIG. These are provided so that guests can receive the above-mentioned services (i) to (x). Note that (233) is a display lamp, and (250) is a printer.

Further, signal access between the center (100) and the terminal device (200'') is performed by polling the computer (30).

In other words, for simplicity, 1024 terminal devices (200
) are (101) to (164).

(201) ~ (264) ,... (1601) ~ (
1664), the downlink control signal channels (108 to 120 MHz) are divided into 16 channels D31 to DSIG as shown in the upper half of FIG.
For example, channel DSI includes terminal devices (101) to (1).
064 terminal devices (iol) to (i64) are allocated to one channel DSi (i=1 to 16).

Then, in each channel DSi, the period τ
1 to τ64 are repeatedly set, for example, channel DS
Each channel DSi
A code signal specifying the terminal device (ij) is sent during the period τj (j=1 to 64) of the smell "ζ".In this case, this code signal is, for example, an 8-bit serial signal, and 1 bit is 1 msec, therefore, the period τ
j is 8 m seconds, and one cycle of period τ1 to τ64 is 5 m seconds.
It becomes 12 msec (=8 msec x 64). That is, on any channel, all terminal devices are sequentially designated repeatedly every 512 msec with a shift of 8 msec. This designation is performed simultaneously for 16 channels.

On the other hand, the same applies to uplink channels (10 to 20MHz), as shown in the lower half of Figure 4.
It is divided into 6 channels USx~USt6, and 64 terminal devices are connected to one channel USi (1101)~
(i64) is assigned. For example, in channel tlsz, the specified period τ of the terminal device (101)
The period T1 delayed by 9 bit periods from 1 is the terminal device (
In channel USi, the period Tj that is delayed by 9 bits from the specified period τj of the terminal device (ij) is considered as the return period of data from the terminal device (i j). This is considered a return period.

In other words, if data is sent during period Tj of channel LJSi, it is considered to be from the terminal device (ij).

Therefore, when control signals are accessed between the center (100) and the terminal device (200), this is done as follows.

For example, the number of a certain terminal device (200) is (102)
Assuming that there is data to be sent from this terminal device (102J) to the center (100), this data is temporarily stored in the computer (201).
In channel DS1, when one poll of center (100) is received, the signal is transmitted from center (100)→
Cable (300) → Distributor (400) – Filter (2
11) - Return circuit (202: → Computer (201)
"ζ is supplied to the computer (201) through the line, and the computer (201) determines whether or not the poll is for itself. If it is not polling for itself, no processing is performed, and polling for itself is performed. Note that this waiting time is at most one cycle of polling, that is, 512 msec.

Then, when the terminal device (102) is polled during the period τ2, the stored data is
Computer (201) → Modulation circuit (203) → Filter (212) → Distributor (400) - Cable (300)
) → Channel US of the center (100) line
z to the center (100), and since this data was sent in period T2 on channel US1,
At the center (100), it is regarded as coming from the terminal device (102) and predetermined processing is performed. In this case, if necessary, the center (100) and the terminal device (10
2) A handshake is performed between the two.

FIG. 6 shows an example of the appearance of this terminal device (200),
The receiver (240) is installed on a stand (rack) (270) and the upper part (271) of the stand (270).
The television signal system circuit is housed in the stand (270
) includes a memory device (225), a computer
(201), a printer (250), a speaker (not shown), and the like are arranged.

The above-mentioned items (i) to (x) are realized by the following operations. In the following explanation, it is assumed that the number of the terminal device (200) used by the inn and the guests is (102).

(i) Viewing TV broadcasts In this case, when the guest turns on the TV switch St of the remote control unit (231), this is determined by the computer (201).

Then, when you turn on the desired channel among the channel switches Sc of the unit (231) (or operate the sweep switch S-), this is determined by the computer (201), and the tuner device (221) Tune to the channel specified by Uniso 1- (231).

Therefore, the tuner device (221) selects the desired one among the television signals sent out from the center (100), and the video and audio signals are transmitted from the tuner device (221) to the switch circuits (223) and (22).
4) to the receiver (240). Therefore,
Guests are free to watch any channel of television broadcasting.

Furthermore, since CATV broadcasts are sent out from the center (100) using available channels of current TV broadcasts, they can be viewed in the same way.

(ii) BGM In this case, if you turn on the BGM switch circuit of the remote control unit (231), this will cause the computer (20
1), the mode is set to receive FM broadcasting, and the switch circuit (224') is switched to the state opposite to that shown in FIG. Then, when the sweep switch Sw of the unit (231) is operated, the reception frequency of the tuner device (222) is swept, and when there is an FM broadcast, the sweep is stopped once. Therefore, the user can listen to the desired FM broadcast.

Furthermore, since the audio signal from the player (14) is also converted into an FM signal and sent out, it can be listened to in the same way.

(iii) Screening of Movies Movies are constantly being played back by the players (15A) and (16A) and are being sent out on specific channels, so when the movie switch Sm of the remote control unit (231) is turned on, this is the computer (201). ), the tuner device (221) becomes tuned to that particular channel, and therefore, the movie can be watched on the television receiver (240) in the same way as in the case of item (i).

Incidentally, when a plurality of movies are being sent out using a plurality of channels, selection can be made using the channel switch Sc as in the case of item (i).

(X) Others (How to use this system) When you turn on the guide switch Sg of the remote control unit (231),
This is determined by the computer (201), the tuner device (221) is set to the still image channel selection state, and the terminal device (102) is set to the center (10
When polled from 0), a request signal is returned.

Then, at the center (100), in response to this request signal, one frame of the video signal of the image shown in FIG. It is converted and sent out from the center (100). However, at this time, the number of the terminal device (200) (
102) is added.

Then, in the terminal device (102), since the tuner device (221) is tuned to the channel of the one-frame television signal that has been sent out, the television signal is received and the tuner device (221) ) supplies a terminal code to the computer (201). Then, in the computer (201), it is determined from this terminal code whether the television signal is for itself, and the terminal device (102)
Since this is a television signal for oneself, the video signal (1 frame) obtained from the tuner device (221) is stored in the memory device (225) and is repeatedly played back (still playback). Further, the switch circuit (223) is connected in a state opposite to that shown in FIG.

Therefore, the seventh
The image shown in the figure is obtained.

Therefore, when the customer turns on the switch "5" of the channel switches Sc of unit 1-(231), this is sent to the center (100) when it is the next bow link from the center (100).

Then, in the center (100), one frame of an image (explanatory text) explaining how to use this system is played from the player (16B) as in the case of Fig. 7, and a terminal code is also added to this. sent out. Then, in the terminal device (102), the signal is transmitted to the memory device (
225) and is played repeatedly,
Therefore, a still image of its usage is sent to the receiver (240).
will be displayed.

Then, when the customer turns on the forward switch Sf of the unit (231), the above operation is repeated and explanatory texts are displayed one after another. In addition, unit (231)
When the backward switch Sr is turned on, the explanation display returns to the previous screen.

(iv) Guide to movies, theaters, etc. In this case, by turning on the guide switch Sg, the receiver (240) will display the screen shown in Fig. 7. At this time, if you turn on rlJ of the switches Sc, , the following operations are similar to those in the case of item (x) above. However, in this case, one frame of image is played back by the sheet recorder (17) instead of the player (16B).

(V) Shopping In this case as well, shopping is carried out by turning on switch "2" of the switches Sc following the guide switch Sg and following the screen in FIG. ) and (16B) are used together.

That is, in the case of fashion, for example, the player (15B) sends out a video of a fashion show, and when you find a piece of clothing that you like, turn on the enter switch Se of the unit (231), and this is sent to the center (100 ).

Then, at the center (100), the player at this time (
The address of the disk of the player (16B) is specified based on the address signal being played from the auxiliary track of the tape 15B), and based on that address, various information regarding clothes when the switch Se is turned on, such as: Images of fabrics, manufacturers, prices, etc. are reproduced, and thereafter various guidance is provided by the player (16B) in the same manner as described above. Also, if the forward switch Sf of the unit (231) is turned on, the player (15A)
You will be redirected to the video from.

When making a purchase, the player (16B) plays an image asking how to purchase (for example, when, how many, etc.), and as in item (x), an interactive unit (231) is played.
) to answer the question.

Data such as the price of the product is then stored on a computer (
30) and is also output to a printer (42).

(vi) Reservation Also, when the guide switch Sg is turned on and the screen shown in Figure 7 appears, if the switch "3" of the switches Sc is turned on, the switch is turned on in the same way as in the case of (x). S
Every time you turn f on, an image of the dish will be displayed. So, if you turn on the switch Se for the desired dish,
This is ordered.

In addition, seats can be reserved interactively in the same manner as in section (v).

(vi) Absence service This is a display lamp (233) of the terminal device (102) that is processed by the computer (30) on the center (100) side.
is lit. Therefore, when the customer turns on the terminal device (102), the recorder (17) plays back one frame of the screen that has been recorded in advance using the camera (18), and this is the case in item (X). Similarly, the receiver (240
) is displayed.

Therefore, the customer can know about the guests who are absent.

(viii) Following the checkout guide switch Sg, the
When the switch 4 is turned on, when polled, it is transmitted to the computer (30), and the main computer (40) sends the entire charge including the accommodation fee and the shopping fee mentioned in (v) to the terminal device along with the details. (
102), and this is output to a printer (250).

Therefore, the customer can know the price and its details in advance, so there is no need to wait at the front desk.

(i) Information This is a terminal device (i) that requires the output of an image or camera (I8) that has been set in advance on the player (16B) by operation of the computer (30) in the center (100).
200) and displayed.

Note that when outputting from the player (16B), it is also sent in units of l frames, and is serialized by the memory device (225).

FIG. 8 shows the waveform when one frame of video signal (TV signal) is sent from the center (100) to the terminal device (102), where ph is the horizontal synchronization pulse, Pv is the vertical synchronization pulse, and B S Haha 71. I-signal,
The numbers from 1 to 525 are line numbers. As described above, the terminal code TC specifying the terminal device (102) is repeatedly inserted into the 1st O line to the 16th line during the vertical blanking period, and this is, for example, a 20-bit serial code. It is a digital signal, and the terminal device (1
02) and a control signal.

Then, the terminal device (102) determines that the video signal is sent to itself from the address signal in the terminal code TC, and also stores this video signal in the memory device (225) according to the control signal. It is determined that it is stored and then repeatedly retrieved and provided to the receiver (240).

Therefore, even if this video signal is only one frame, it is sent to the specific terminal devices [xo2] i, . . . z and is continuously reproduced as an image.

FIG. 9 shows the handshake between the center (100) and the terminal device itself 02. Zunawara ■ Center (1
00) to the terminal device (102).

■ Data is sent from the terminal device (102) to the center (100).

(2) An acknowledge signal is sent from the center (100) to the terminal device (102).

■ An end code is sent from the terminal device (,102,) to the center (100).

Then, in (2), the center (100) is executing the necessary processing at the time of transmitting the acknowledge signal.

As described above, in this CAT■ system, when sending a still image from the center (100) to the terminal device (200), only one frame is sent and this is sent to the terminal device (200).
0), the memory device (225) is used to repeatedly reproduce still images, so the center (1
00) and a plurality of terminal devices (200).
Even if the capacity of 300) is small, a large number of still images can be transmitted. In other words, since the time required to send l frames of images is l/30 seconds, still images can be sent to 30 terminal devices (200) per channel in one second. If one still image is requested for each channel, the still image can be sent to 150 terminal devices (200) per channel. In the example of Fig. 3, the bands (120 to 174 MHz, 216 to 402 MHz)
If MHz) is allocated to still images (videos can be allocated to empty broadcast channels), this is the capacity for 40 channels, so 6000 units (
This means that it is possible to respond to requests from terminal devices (200) (=150 devices x 40 channels). Or, since the operating rate of general telephone lines is usually less than 5%,
In the case of the figure, 120,000 units (= 6,000 units 15%
) can respond to requests from the terminal device (200).

Thus, according to this CATV system, a large number of still images can be sent even with just one coaxial cable (300). Moreover, the coaxial cable (300
) can be done using existing cables, so there is no cost involved.

By the way, in the case of the above numerical example, the number of terminal devices (200) per channel is 64, but this is 500, and these 500 are divided into 8 terminals per channel as described above.
When polling with bits (8ms), 1 bit of polling
The period becomes 4 seconds (-8 m-seconds x 500 units). Therefore, even if a guest makes a request at a certain terminal device (200), in the worst case, it will take 4 seconds for the request data to be sent to the center (100).
The response of the terminal device (200) becomes extremely slow.

This invention attempts to solve these problems.

Therefore, in the present invention, instead of the polling shown in FIG. 4, for example, polling as shown in FIG. 10 is performed.

In other words, for simplicity, the terminal device (200) is 16×5.
00 units, and each number is (1001) to (15
00), (2001)~(2500), (
16001) to (16500). and,
Figure 10A.

As shown in B, channel DSi, 1Isi (i
= 1 to 16), a down channel 5DSi and an up channel SUS i are set, and this channel 5
Polling is performed for all terminal devices (1001) to (16500) using the DSi and 5O5i as in the case of FIG. 4.

However, polling using these channels 5DSi and 5USi is limited to terminal devices (ij) (j=1 to 50).
This is to check whether the power (power switch) of 0) is on or off, and if, for example, "all 0" is returned as data during the period Tj of channel 5USi, the power of the corresponding terminal device (ij) is turned off. If, for example, "all l" is returned, the corresponding terminal device port j] is considered to be powered on, and this on/off state is stored in the center (100).

On the other hand, as shown in FIGS. 10C and 10D, in the original channels DSi and USi, polling is performed only for terminal devices (200) whose power is on. In other words, the center (100) is channel 5DSj, 5U
Since the power on/off state of each terminal device (ij3) is detected by polling using Si, based on this detection result, polling is performed for the terminal device (200) whose power is on, and the power is turned off. A terminal device (2
00) is not polled. In addition, the first
In Figures C and D, the terminal device (io02),
[1008), (i012).

... (149B) is turned on.

Therefore, if the number of terminal devices (200) that are turned on is N, the polling cycle on channels DSi and USi is 8N milliseconds, but the terminal device (200) is
If the usage rate of 00) is 5%, then N-25 (500 units x
5%), so the polling cycle is 0.2 seconds (-8 msec x 25 units). That is, even in the worst case after a guest makes a request, the data of the request will be sent to the center (100) 0.2 seconds later, resulting in an extremely quick response.

Note that the cycle of polling the power on/off status of the terminal device [i j) using channels 5O3i and 5USi is 4 seconds, so when the power of a certain terminal device (i j) is turned on from off, the center (100), it takes 4 seconds in the worst case, but this time is the same as the warm-up time of the television receiver (240) when the terminal device (2 (10)) is turned on. That is, even if the power of the terminal device (200) is turned on, the screen of the television receiver (240) does not appear for about 4 seconds, so there is no problem.

FIG. 11 shows an example in which the above-described polling is performed by hardware at the center (100). That is, FIG. 11 shows channel 5DSi of the center (100).
, 5USi, DSi, and USi are shown, but in the code signal forming circuit (61), the terminal device (
A code signal specifying 1001) to (1500) is sequentially formed, this signal is made into a modulated signal of channel 5DSi in a modulation circuit (62), and this signal is sent out to a cable (300) through a bandpass filter (63). It will be done.

In addition, the signal from the cable (300) is supplied to the band pass filter (64) to extract the return signal of channel 5USi, and this signal is supplied to the demodulation circuit (65) to transmit the signal to the terminal devices (1001) to (1500). A signal indicating the on/off state of the power supply is sequentially demodulated, and this signal is supplied to the detection circuit (66), and a code signal from the formation circuit (61) is supplied as a signal indicating the number of the polled terminal device, Currently, it is determined which terminal device the data returned from the terminal device (ij) is from, and the power on/off status of the terminal devices (1001) to (1500) is sequentially detected, and this detection result is The data are sequentially stored in the memory (67).

Then, in the code signal forming circuit (71), a code signal specifying the terminal device whose power is turned on among the terminal devices (i j) is sequentially formed based on the data in the memory (67). The signal is made into a modulated signal of channel O3+ in the modulation circuit (72), and this signal is passed through the bandpass filter (73) to the cable (30).
0).

Further, the signal from the cable (300) is supplied to the bandpass filter (74) to extract the return signal of channel USi, and this signal is supplied to the demodulation circuit (75) to Signals indicating requests from terminal devices whose power is on are sequentially demodulated, and these signals are supplied to the decoder (76) and also to the formation circuit (
The code signal from 71) is supplied as a signal indicating the number of the polled terminal device, and it is determined from which terminal device the currently returned data is sent, and the data is sent to the head end (10). Supplied.

FIG. 12 shows the part related to polling of the terminal device (200), and in this example, the terminal device (200)
is the number (1002). That is, even if the terminal device (200) is turned off (power switch), the microcomputer (201) and its peripheral circuits are not turned off and remain energized. Then, the channel 5DSi signal from the cable (300) is extracted by the bandpass filter (2'61), and this signal is supplied to the demodulation circuit (262) to demodulate the code signal. 201) and the device itself (terminal device (1002)
), and if it is not directed to you, it is ignored, and if it is directed to you, data indicating the on/off state of the electric power switch (power switch) is formed, and this data is sent to the modulation circuit (271). The modulated signal of channel 5USi is sent to the cable (300) through the bandpass filter (272).

When the power is on, polling is performed by channel DSi, and necessary data is returned by channel USi.

FIG. 13 shows a terminal device (20
FIG. 14 shows a flowchart for polling the power on/off state of the center (100).
) shows a flowchart when polling a terminal device (200) whose power is on.

However, in this example, when the terminal device (200) is powered off, it is sent back to the center (100) through channel USi.

Furthermore, FIG. 15 shows a flowchart of operations in the terminal device (200). Note that these can also be realized by software of the microcomputers (30) and (201).

As described above, according to the present invention, the terminal device (200)
Even if there are a large number of terminal devices, only the terminal devices whose power is turned on are polled, so that responses to requests from the terminal devices can be made faster.

[Brief explanation of drawings]

1, 2, 11, and 12 are system diagrams of an example of the present invention, and FIGS. 3 to 1θ, and 13 to 15 are diagrams for explaining the same. (100) is a CATV center, (200) is a terminal device,
(300) is a coaxial cable. 1i15 figure

Claims (1)

[Claims] The CATV center and a plurality of terminal devices are connected by a common cable, and among the plurality of terminal devices, the terminal device whose power is turned on is registered in the CATV sezota, and based on this registration, the plurality of terminal devices are connected by a common cable. Of the terminal devices,
A CATV system in which °ζ polling is performed from the CATV center through the cable only to the terminal device whose power is turned on.