JPH0310491A - Cctv data communication system - Google Patents

Abstract

PURPOSE:To reduce installation cost and its trouble by superimposing data onto an AC power line as an FSK(Frequency Shift Keying) or a PSK(Phase Shift Keying) modulation signal to apply 2-way communication. CONSTITUTION:Each terminal equipment 3 of a CCTV(Closed-Circuit Television) system is connected to a 75OMEGA coaxial cable 1, receives each antenna input of VHF, UHF, a video and audio output of a transmitter 8 from a player 7 and outputs a video and audio data converted into a frequency signal corresponding to the channel of a television receiver on market. Then the transmission data is modulated into an FSK or PSK modulation signal and superimposed on an AC power supply line 11 to attain 2-way communication between a CCTV terminal equipment 3 and the computer system 2. Thus, the cost is reduced and the system is simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to CCT V (C1osed-Circui
The present invention relates to data communication between a terminal device installed in a guest room of a hotel or the like and a center computer in a televi-sion system.

[Prior Art] CCTV data communication systems generally include a communication system that shares a TV public listening line and a data line system that uses an interface.

The former, as shown in the block configuration in FIGS. 4 and 5, is a TV antenna common listening line (coaxial cable) 101.
using the center computer system 102 side and C
Using an FSK high frequency modem or PSK high frequency modem 104, 105, and a center modem unit 106 provided in the CTV terminal 103, data is communicated on a carrier such as 40 MHz or 70 MHz. 90
Since frequencies above MHz are used for VHF, UHF, TV signals, and CCTV signals, communication is performed bidirectionally below 90 MHz. Note that video and audio signals are transmitted from a player 107 (VTR or laser disc) to a transmitter 108 to the TV public listening line 101.

In this system, if the existing TV common listening line 101 is not old, it can be used to a large extent simply by converting the branch and distributor to bidirectional. On the other hand, the CPU 109 inside the terminal device 103
The conventional data line method, in which modems 104, 105, etc. for data communication with the player are very expensive, carries video and audio signals from the player 107, as shown in the block configurations of FIGS. 6 and 7. In addition to the 75Ω coaxial cable 111, a data communication line 112 is separately provided, and R, 84, 22-A is provided between each terminal device 103 and the center 102.
Interfaces 113, 114 capable of equal long distance communication
, 115, 116 for communication.

In this method, the communication transceiver ICs of the interfaces 113 to 116 are low cost.

On the other hand, equipment costs and construction work are costly. Therefore, this becomes a problem when the number of terminals exceeds 100, so if the number of rooms increases (for example, 1000 to 2,000)
0 room, etc.), the former method will be adopted.

[Problem to be solved by the invention] In this way, the conventional CCTV data communication system
When using an antenna common listening line (75Ω coaxial cable), FSK and PSK high frequency modems are extremely expensive, and when data lines such as R and S-422-A are wired separately for communication, construction work is required. There are problems such as the cost and effort involved.

The present invention solves these problems and allows data to be
C that is communicated by superimposing it on the AC power line as an SK or PSK modulated signal to save construction costs and labor.
The purpose is to provide a CTV data communication system.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a CCTV terminal that performs data communication between a CCTV terminal and a center computer.
In a TV data communication system, transmission data is sent to both the CCTV @ terminal device and the center computer side via FS.
A driver modulates the FSK or PSK modulated signal and sends it to the AC power line, and a receiver that receives the FSK or PSK modulated signal on the AC power line, detects it, and demodulates it to data.
It is superimposed on the power line to perform bidirectional communication.

"Operation" According to the above configuration, the transmission data is sent to FSK or P
By modulating the SK modulation signal and superimposing it on the A and C power lines, bidirectional communication can be performed between the CCTV terminal and the center computer.

[Example] Figure 1 shows the overall system configuration according to an example of the present invention, Figure 2 shows the professional configuration of the CCTVI terminal, and the FSK to R, S 232C conversion unit on the center computer side. The configuration of each soto is shown in FIG.

In this system shown in Fig. 1, c c 'r' v
Each terminal device 3 is connected to a 75Ω coaxial cable 1,
VHF, tJHFO propagated through 5Ω coaxial cable 1
Each antenna input, as well as VTR and laser disc (LD)
) etc., the video and audio output from the transmitter 8 is received from the player 7, and the video and audio are output after being converted into frequency signals corresponding to commercially available TV channels.

Further, the center computer system 2, each terminal device 3, and the internal terminal are connected through an AC power line 11, and data is superimposed on the same line to perform bidirectional half-duplex communication. Note that 12 and 13 indicate the power plugs and outlets on the center side and the terminal side, respectively.

In order to perform data communication using the second AC power line, as shown in FIGS. 2 and 3, carrier current transceivers 18 and 34 are installed in the terminal device 3III and the center 2 side conversion unit 31, respectively. There is. As this carrier current transceiver 18.34, for example, LM1893 manufactured by National Semiconductor Corporation may be used.

First, the terminal device 3 will be explained with reference to FIG. The terminal device 3 is
An up/down converter 14 having an antenna input and a TV output, a CPU 15 for data communication, a key power matrix 16, a display matrix 17, and the carrier current transceiver 1 for data input/output described above.
8, a power transformer circuit 19, and an FM for input signals.
It consists of a noise canceller 20, a time domain filter 21, and the like.

The carrier current transceiver 18 transmits the data to be transmitted at FSK (Frequency 5hift).
Keying) This is an IC that integrates a driver that converts it into a modulated signal and sends it to the AC power line, and a receiver that receives and detects the FSK signal on the AC power line and demodulates it into data. This carrier current transceiver 18 carries data on a carrier of 50 KHz to 300 KHz at about 2 V using FSK modulation.

The receiving side has a sensitivity of about 2 mV and performs FSK demodulation and TTL
The level data is output and sent to the CPU 15 as R,x (received data). By using this carrier current transceiver 18, approximately 60 d on the AC power line
B: Long distance communication (approximately 500 meters) is possible before attenuation.

By the way, R3-422-A etc. can communicate up to 1200 meters (theoretical value), so if you want to communicate up to this distance, you need to prepare a repeater using a carrier current transceiver (for R8-422-A, parallel However, the carrier current receiver allows you to select various carriers, so by performing parallel communication, R,
Communication to the same number of terminals as the S-422-A method can be performed without a repeater.

Furthermore, it is common for AC power lines to contain strong noise from electric drills, other motors, and the like. The IC that constitutes this carrier current transceiver is designed to have high noise immunity characteristics for FSK, but in order to further increase the noise margin, a noise canceller 20 (for example, an IC manufactured by NEC, μPc1176c) is installed on the Rx line. It is set up in By using this IC in the Rx section to the CPU 15 for data communication, it is possible to greatly improve the noise immunity in this field.

Also, the output of the carrier current transceiver 18 is CP
Since it is possible that antenna noise may enter before reaching U15, a time domain filter 21 is provided.

FSK~R on the center computer 2 side shown in Figure 3
, 5232C conversion unit 31 has almost the same block configuration as that of the terminal device 3 described above.

That is, the conversion unit 31 is connected to the center computer 2 via the R3232C gaple 32.
, 3232 C connector 33, the above carrier current transceiver 34, power transformer circuit 35, and F
It consists of an M noise canceller 36, a time domain filter 37, and the like.

In the above configuration, the center computer 2 polls each terminal device 3 and determines the terminal address N.

The terminal device 3 transmits data such as which pay channel was received for how many hours from the terminal device 3 to the center computer 2 through the AC power line 11.

Next, the advantages of this embodiment will be explained. The conventional and commonly used method of sharing the TV listening line with data communication is a high frequency R, F modem unit (PSK, F modem unit).
(SK, etc.) are very expensive, and at the same time, the center modem on the center computer side is also expensive. On the other hand, the method of this embodiment does not require such a modem, and therefore costs can be significantly reduced.

In addition, as a method of wiring the conventional data line as a separate line, R
Although the method using 8-422-A and the like has been described above, this method involves indoor wiring work. On the other hand, the method of this embodiment eliminates the need for such wiring work, making it possible to significantly save labor.

However, since the signal passes through the power transformer circuit, the transformer has a large inductance, and while it strongly cuts noise, the signal loss is especially large in the high range.Therefore, in models that do not have high transmission rates, it is necessary to have an independent transformer. . Furthermore, due to transmission rate constraints, this embodiment can be said to be suitable for medium-sized systems. On the other hand, in order to create a large-scale system, it is necessary to increase the baud rate and polling speed, so measures such as parallel communication using multiple carrier frequencies are required.
t+dXN (where N is the type of carrier).

In addition, although the case of FSK modulation was explained above,
P S K (Phase 5hift Keying
) Modulation may also be used. Furthermore, the conversion uni-soto 31 shown in FIG. 3 may be built into the computer main body.

[Effects of the Invention] As described above, according to the present invention, transmission data is FSK or PSK modulated and superimposed on the AC power line to perform bidirectional communication, so that it is possible to perform two-way communication using the conventional TV antenna common line. It is not necessary to use an expensive FSK/PSK high frequency modem, which is required in data communication systems, and costs can be reduced. Further, since there is no need for construction in the case of a communication system in which a data line using an interface such as R8422-A is wired as a separate line, cost and labor savings can be achieved.

[Brief Description of the Drawings] Fig. 1 is an overall system configuration diagram according to an embodiment of the present invention, Fig. 2 is a block diagram of a CCTV VIII terminal device, and Fig. 3 is a block diagram of a CCTV VIII terminal device.
The figure shows FSK~R,S232 on the center computer side.
Figure 4 is a diagram showing the overall configuration of a conventional system; Figure 5 is a diagram showing the configuration of a conventional terminal; and Figure 6 is a diagram showing an example of a conventional system. , FIG. 7 is a block diagram of the terminal device of this example. 2...Center computer system, 3...CC
TV terminal device, 11... AC power line, 18... carrier current transceiver (including driver and receiver).

Claims (1)

[Claims] (1) In a CCTV data communication system that performs data communication between a CCTV terminal and a center computer, transmit data is modulated into an FSK or PSK modulated signal and connected to an AC power line on each side of the CCTV terminal and center computer. A driver that sends the FSK or PSK modulation signal to the
A CCTV data communication system characterized by superimposing an SK modulated signal on an AC power line to perform bidirectional communication.