JPH0120582B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention utilizes a limited occupied frequency using a plurality of devices (hereinafter referred to as videophones) having video transmission and reception functions in a local area network. This invention relates to a television telephone device that enables two-way communication by effectively utilizing the band.

Conventional configuration and its problems Typical cable television broadcasting equipment is a system that focuses on the simultaneous rebroadcast function and has multiple stations receiving foreign television broadcasts, and the transmitting station transmits The receiving side selects one of a plurality of frequency bands (channels), and does not enable mutual communication between stations.

Moreover, since videophones that enable mutual communication between stations have a bidirectional function, each videophone transmits each other's video and audio using its own station frequency band. Individual frequency bands must be assigned to videophones, and in order to make videophones possible as a local network, the number of videophones that can be connected is limited depending on the occupied station frequency band used.

OBJECT OF THE INVENTION The present invention eliminates the conventional drawbacks as mentioned above,
To enable multiple stations with bidirectional functionality to communicate efficiently with each other using a single coaxial cable, channels are automatically searched for free channels within a limited occupied frequency band. The purpose is to realize an expandable local network that can connect several times as many combinations without being limited in number.

Structure of the Invention In the present invention, each video telephone station can selectively modulate the video signal to be transmitted into a plurality of channels, searches for a channel that is not used at the time of transmission, and transmits the video signal on that channel. At the same time, a data control signal indicating the identification number of the destination station and the aforementioned selected channel is sent, and the video telephone station with the matching identification number sets the reception channel according to the data control signal and receives the data. This made it possible.
That is, if stations having a large number of transmittable channels communicate with each other in random combinations at once, the channels in use overlap, resulting in a situation where communication is impossible. Therefore, we set up a control center (hereinafter referred to as an empty channel search device) that searches for unused station frequency bands within the occupied frequency band.
This allows for smooth communication.

On the other hand, the receiving station detects the channel of the transmitting station from the data control signal and receives the signal.

Similarly, the receiving stations are also equipped with the above-mentioned free channel search device, and mutual communication is enabled by searching for free channels and transmitting video signals using unused channels.

An empty channel search device having the above-mentioned functions configures a path network using a single coaxial cable as a medium, and enables smooth communication with any partner station.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 2 is a block diagram of a videophone that constitutes a local network.

First, when transmitting a signal to call the other station (hereinafter referred to as B station) 17 from the originating station (hereinafter referred to as A station) 16, the identification number assigned to B station by the tuning operation device 15 is transmitted. When a manual input is made, the data control circuit 13 of the block diagram of the video telephone apparatus shown in the figure generates a call request signal to the B station 17. Then the free channel search circuit 7
detects an empty channel on which it can communicate with the B station 17.

Next, the video camera 10 and the microphone 11
The signal generated by the RF converter 5 generates a standard television signal. The RF converter 5
is equipped with a plurality of channel frequency generation circuits, and transmits the optimum frequency value in response to a data control signal generated from an empty channel search circuit 7 indicating a selected channel. At the same time, the aforementioned B station 17
A communication request signal with the identification number and data control signal is outputted to the transmission circuit 4, superimposed by the synthesizer 3, and sent out through the bidirectional distributor 2 and the coaxial cable 1.

On the other hand, the B station 17 uses coaxial cables 1a, 2a,
A call request signal from station A 16 is sent to data control circuit 13a through 3a, and by decoding the communication request signal, station B learns from its own identification number that a call is requested. At the same time, the data control circuit 13a is driven to operate the channel selection circuit 8 with a control voltage according to the data control signal, and the channel selection circuit 8 is transmitted to the selection circuit 9 so as to match the frequency value transmitted from the A station 16. A tuning command is output, and the image can be received by the receiver 14a.
As a result, the A station 16 has established a communication channel with the B station 17.

In order for the B station 17 to subsequently start a call with the A station 16, the data control circuit 13a of the B station 17 generates an answer back signal, instructs the empty channel search circuit 7a to search for an empty channel, and searches for an empty channel as described above. The frequency band value obtained by detecting the channel is
The answer back signal generated from the RF converter 5a and containing the data control signal indicating the selected channel is superimposed on the answer back signal 4a, 3.
A, 2a, 1a, 2, 3, and 4 are sent to the data control circuit 13a of the A station 16. This data control circuit 13 decodes the received answer back signal, learns the frequency band value of the channel selected by the B station, generates a control voltage with it, activates the channel selection circuit 8, and transmits from the B station 17. The selection circuit 9 tunes to the received frequency band value, and it becomes possible to receive the video signal.

As mentioned above, since the communication channel between the A station 16 and the B station 17 has been established, it is now possible to talk to each other while viewing the video, and to use the channel selection operation button to specify the other station with which you wish to talk. By simply operating the RF converter, the RF converter automatically searches for a vacant channel from among the multiple channel frequencies possessed by the RF converter, making it possible to effectively use occupied frequencies. This allows communication without being limited by the number of channels.

Note that when station A calls station B, if station B is in the middle of a call with another station, no answer call signal is sent from station B, so the call cannot be made. The above describes in detail the two-way communication procedure between two stations, but if a free channel is not searched, that is, if one channel is assigned to a videophone call, the path network that allows the use of four channels If we assume that only 4 videophones can be connected on the network,
By searching for an available free channel from among the multiple channel frequencies in the RF converter, five or more videophones can be connected on the network. Therefore, cable expansion in the network and addition of videophones can be easily performed. That is, the C station 18, D station 19, and E station 20, which have the same functions as the A station 16 and B station 17, constitute a bus network using one coaxial cable as a medium, and as described above, A station 16
And the same mutual communication as that carried out in the B station 17 can be performed in the C station 18, D station 19 and E station 20.

Effects of the Invention As described above, according to the present invention, an empty channel can be automatically searched for and communicated within a limited occupied band, and lines can be used effectively.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video telephone device using an empty channel search device according to an embodiment of the present invention, and FIG. 2 is a block diagram of an example of a bus network of the video telephone device. 1, 1a, 1b, 1C, 1d, 1e...Coaxial cable, 2, 2a, 2b, 2c, 2d, 2e...Bidirectional distributor, 3, 3a...Distributor and combiner, 4, 4a
... Signal transmitting/receiving circuit, 5, 5a... RF converter, 6, 6a... Modulator, 7, 7a... Vacant channel search device, 8, 8a... Tuning circuit, 9, 9a... Selection circuit, 10, 10a... Video camera, 11,1
1a... Microphone, 12, 12a, 12b,
12c, 12d... Own station monitor receiver, 13, 1
3a...Data control circuit, 14, 14a, 14b,
14c, 14d...TV receiver, 15, 15a,
14b, 14c, 14d...tuning operation circuit, 16...
A-station videophone call, 17... B-station videophone call, 18...
C station video call, 19...D station video call, 20...
E station video phone.

Claims (1)

[Claims] 1. A plurality of video telephone stations, each with a different identification number, are connected to the same coaxial cable, and each of these video telephone stations is selected from a plurality of predetermined channels according to a data control signal. transmitting means that modulates a video signal to be transmitted into a frequency band corresponding to one channel and sends it out to the coaxial cable; an empty channel search means for applying a data control signal to the transmitting means to select a channel other than the used channel from the channels of the channel; and a data control indicating the selected channel together with the identification number of the destination station to which the transmission is to be made. A means for sending a signal to the coaxial cable, and detecting the identification number sent by the coaxial cable, and when it is confirmed that it is the identification number of the own station, responding to the data control signal sent with the identification number. 1. A video telephone device, comprising: receiving means for selecting a receiving circuit for a given channel.