JPH01174143A - Network terminator - Google Patents

Abstract

PURPOSE:To prevent the infiltration of induced noise or noise from the idle terminal of a terminal equipment by providing a network terminator between a drawing line and a subscriber's wiring in a broad band network using a CATV. CONSTITUTION:The network terminator 10 is accommodated in an enclosure subjected to electromagnetic shield and shielded electromagnetically against noise incoming externally. Then a normal signal sent between a network center equipment and a terminal equipment 3 connecting to a subscriber's wiring 2b is sent via a 1st unidirectional buffer (a part or all of the received signal is transmitted to the wiring 2b) and a 2nd unidirectional buffer (the signal from the wiring 2b is transmitted to a drawing line 2a). Even if any noise is infiltrated from an idle terminal 12, the transmission of noise to the drawing line 2a is blocked by the 2nd unidirectional buffer and the induced noise is also blocked.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to a network in which a plurality of subscriber premises wiring are connected to a tree-shaped or bus-shaped transmission path through drop-in lines. This invention relates to the network termination device used.

(Prior technology) Multimedia Q that integrates data, video, and audio information
As one type of network, a broadband network based on CATV has been put into practical use. For example, as shown in FIG. 6, this broadband network has a configuration in which a center device 1 is disposed at the most upstream position, and terminals 3 at the terminals 3 are connected to a transmission path 2 made of a coaxial cable formed in a tree shape. . The transmission line 2 is divided into upstream and downstream transmission lines based on frequency bands, and each of these transmission lines is frequency-divided to transmit the various information described above.

By the way, the terminal side in this type of network is constructed by connecting a drop-in line 2a led from the network side to the subscriber premises wiring 2b via a protector 5, as shown in FIG. Ru. This subscriber premises wiring 2b consists of a transmission line network that is branched and distributed via a distributor 6 or a branch 7 as necessary and installed in the home. This subscriber's premises wiring 2b
The terminal devices 3 are connected to the terminals 8 of the subscriber premises wiring 2b, respectively, and a terminating resistor 9 is connected to the end of the subscriber premises wiring 2b for matching termination.

However, in this subscriber premises wiring 2b, the terminal equipment 3
The terminal 8 to which is connected is usually left open on the wall surface. Terminal 8 left open
easily receives surrounding external noise, and the noise received at this terminal 8 is transferred from the subscriber's premises wiring 2b to the drop-in line 2a.
There is a problem in that the data flows into the center device 1 upstream of the network via the network. For this reason, for the center device l,
Inflow noise from all the open terminals 8 on the network is concentrated, which tends to cause the problem of so-called flow noise.

In addition, all terminals 8 are transparent to the center device.
Since the terminal 8 is connected to the terminal 8, if an interference signal is input from the terminal 8, there is a possibility that the entire system will malfunction (system down).

Furthermore, according to the configuration of the terminal side (wiring in the subscriber's premises) as described above, for example, even if the signal level at the drop-in line 2a is set and managed within a certain range, the signal level in the wiring at the subscriber's premises 2b is There is a possibility that the signal level will change significantly due to branching and distribution. This not only causes deterioration of the S/N of the received signal in the terminal equipment 3, but also causes damage to the transmitter, such as a data RF modem, in the center equipment 1.
In order for the receiver to be able to receive the signal, it is necessary to transmit and output it as a signal with a sufficiently wide dynamic range. Therefore, in order to cope with these problems, it is necessary to improve the performance of the terminal equipment 3 (expanding the dynamic range of the transmitted and received signals), which has the disadvantage of causing an increase in the price of the terminal equipment 3.

(Problems to be Solved by the Invention) In this way, in conventional network systems, the subscriber's premises wiring on the terminal side is simply terminated at the end.
Since the terminal is normally open, problems such as flow noise are likely to occur, and there are also problems in the terminal equipment, such as the need to expand the dynamic range of the transmitted and received signals.

Furthermore, there were other problems such as the entire system being completely vulnerable to the input of interference signals.

The present invention has been made in consideration of these circumstances, and its purpose is to provide a network system suitable for realizing a network system that does not cause problems such as flow noise and the need to expand the dynamic range. The objective is to provide a network termination device.

[Structure of the Invention] (Means for Solving the Problems) A network termination device according to the present invention is formed by connecting a plurality of subscriber premises wiring to a tree-shaped or bus-shaped transmission path through drop-in lines. A coupler is installed between the above-mentioned drop-in line of the network and the subscriber premises wiring, and is formed by terminating a vacant terminal among a plurality of distribution terminals for distributing the above-mentioned drop-in line with a predetermined impedance; a first unidirectional buffer, connected to one of the distribution terminals of the coupler, for transmitting part or all of the received signal from the service line to the customer premises wiring; It is characterized by comprising a second unidirectional buffer that transmits a predetermined signal transmitted from the subscriber's premises wiring to the drop-in line.

In addition to the above-mentioned coupler, the first and second unidirectional buffers, for example, a modem demodulator and a demodulator,
This device is characterized by a structure in which the weekly container and the like are electromagnetically shielded from the outside.

(Function) According to the network termination device of the present invention, the subscriber's premises wiring and the network side drop-in line are insulated from signals other than regular signals, so that the subscriber's premises wiring is not released. Even if noise flows into the terminal, this noise is blocked by the network termination device, so it is no longer transmitted from the drop-in line to the center side via the network, effectively solving the problem of sink noise. It can be resolved.

Moreover, even if a disturbance signal is input from a terminal on the subscriber's premises wiring, since the signal is not a legitimate signal, the transmission to the drop-in line is blocked by the network termination device, The system will not go down due to signals, and effective countermeasures against interference can be taken.

In addition, since the level of the transmitted signal is controlled to be constant by the first and second unidirectional Hanofa provided in the network termination equipment, the dynamic range of the transmitted and received signals at the terminal equipment is controlled to be constant, unlike the conventional system. There is no need to expand in anticipation, and it becomes possible to simplify the configuration of the terminal equipment and lower the cost accordingly.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

The network termination device 10 according to the present invention is a drop-in line 2 of a network in which a subscriber premises wiring 2b is connected to a tree-shaped or bus-shaped transmission line (on the network side) via a drop-in line 2a.
It is provided between the subscriber's premises wiring 2b and the subscriber premises wiring 2b. More specifically, as shown in FIG. 1, a network termination device IO according to the present invention is provided between the subscriber premises wiring 2a connected to the drop-in line 2a via the protector 5 and the protector 5. A network is constructed by connecting the subscriber premises wiring 2b to the network via this network termination device IO.

As mentioned above, the subscriber's premises wiring 2b consists of a transmission line network that is branched and distributed as necessary via the distributor 6 or branch 7 and installed in the home, and the terminal equipment 3 is It has a configuration in which it is connected to a terminal 8 as appropriate, and a terminating resistor 9 is connected to its terminal end for matching termination. In a broader sense, the subscriber premises wiring 2b is constructed including the network termination device 10.

By the way, the network termination device 10 according to an embodiment of the present invention has, for example, a drop-in line (network side transmission line) 2a as shown in FIG.
A coupler 13 is provided with a large number of distribution terminals 11a, llb, . ~lln, and transmits a part or all of the received signal received from the drop-in line 2a via the coupler I3 to the subscriber premises wiring 2b side; 1 of the distribution terminals 11a, 11b, ~lln of the coupler 13
and a second unidirectional buffer that is connected to the subscriber premises wiring 2b and transmits a predetermined signal transmitted from the subscriber premises wiring 2b side to the drop-in line 2a (network side) via the coupler 13. be done.

The coupler 13 is composed of, for example, six distributors (mixers), and distributes and outputs the signals received from the center side via the downlink transmission line of the network to the distribution terminals 11a, llb, to lln, respectively. Distribution terminal 11a, flb,
. . . lln are mixed, and the drop-in line 2a transmits and outputs the signal to the center side via the uplink transmission line of the network.

The first and second unidirectional buffers thus comprise a demodulator and a modulator in a modem, such as the TDMA-S interface modem 14 or the packet data modem 15, and in particular the first unidirectional buffer. As a buffer, there is an amplifier 1B that amplifies and outputs the broadcast signal transmitted via the downlink line of the network, and a frequency converter that converts some of the above-mentioned frequency allocation information on the network and imports it into the in-house wiring side. It is also realized as a vessel 17 or the like. Incidentally, here, the respective outputs of the amplifier 16 and the frequency converter 17 are mixed via a mixer 18 and then output to a so-called home bus via a coaxial cable that constitutes a part of the in-house wiring 2a. It has become a thing.

Further, the S interface side of the TDMA-S interface modem 14 is connected to telephone system wiring of a home bus consisting of two to four twisted pair wires. It is further connected to the data terminal line of the home bus with a packet data modem 15.

The free terminal 11 of the coupler 13 terminated by the terminating resistor 12 mentioned above in 22 is provided with the above-mentioned first and second
unidirectional buffers are connected as appropriate. When not in use, in order to prevent noise from entering the vacant terminal,
Matching termination is performed by the aforementioned terminating resistor 12.

The network termination device 10 configured as described above is housed, for example, in an electromagnetically shielded housing, and is electromagnetically shielded from noise coming from outside. Inside this housing, there is the aforementioned lead-in t12a and in-house wiring 2b.
The input of any signal other than the authorized signal via the terminal is blocked. Note that the above-mentioned coaxial cables, twisted pair wires, data terminal wires, etc. that make up the in-home wiring 2a may be housed in aluminum pipes or the like, or they may be treated with an aluminum sheath and placed inside the home. Also, drop-in line 2a
If the structure is similarly electromagnetically shielded,
It is also possible to effectively suppress incoming noise from entering through the lead-in line 2a.

Thus, according to a network constructed by providing such a network termination device 10 between the network side and the subscriber premises wiring 2b, the network center equipment l and the terminal equipment 3 connected to the subscriber premises wiring 2b Regular signals transmitted between the two are transmitted through the first and second unidirectional buffers, respectively.

Furthermore, even if there is a terminal 8 of the subscriber's premises wiring 2b that is left open on a wall or the like in the home, the noise that enters from the vacant terminal 8 is not the original legitimate transmission signal, so the above-mentioned The unidirectional transmission buffer No. 2 prevents transmission to the drop-in line 2a side.

Therefore, it is possible to effectively prevent the noise mixed in from the subscriber premises wiring 2b from being transmitted to the center equipment 1 side without interfering with the regular information transmission between the center equipment 1 and the terminal device 3 at all. This makes it possible to effectively solve the problem of flow noise, which has been a major problem in conventional systems.

Furthermore, according to the network termination device 10 described above, it is possible to control the level of the signal transmitted and output to the network side to be constant regardless of how the subscriber premises wiring 2b is constructed, and it is also possible to control the level of the signal transmitted and output to the network side to be constant. Since the signal can be appropriately regenerated and amplified and supplied to the subscriber's premises wiring 2b, the signal transmission and reception capability required of the terminal equipment 3 connected to the premises wiring 2b, that is, the dynamic range for the signal, is greatly expanded. There is no need to do so. As a result, it is possible to keep the specifications (dynamic range for signals) required of the terminal device 3 low, simplify the configuration, and reduce product cost.

Further, according to the above-described configuration, even if a disturbing signal is maliciously inputted from the vacant terminal 8, for example, the disturbing signal is not a legitimate signal, so the second unidirectional buffer 7 Transmission to the network side is effectively blocked. Therefore, it is possible to prevent functional failure of the entire system due to the input of interference signals, and it is possible to ensure the reliability of the network.

By the way, in a network configured using the network termination device 10 as described above, the security of the network can be further enhanced by adding, for example, the following management function.

That is, this type of network basically includes a main line amplifier 21 . It is configured by connecting the subscriber premises wiring 22b to the service line 22a which is led to the home via the extension amplifier 221, distributor 23, etc., via the protector 5 and the network termination device 10 according to the present invention. However, at this time, the management device 24 is installed at the most upstream position of the network. This management device 24 is installed even in conventional boat-based network systems to check the status of the main amplifier 21, extension amplifier 22, etc., and manage the operating status of the system. Furthermore, it is provided to manage the status of the network termination device 10.

Therefore, as shown in FIG. 4, for example, the network termination device IO has a wiring 3 for detecting damage to the housing on the wall surface (box and lid) of the housing.
(1) and a switch 32 which is energized according to the opening and closing of the lid.

The housing destruction detection wiring 31 and the switch 32 are connected to a high frequency choke 33, as shown in FIG. It constitutes a series circuit together with the load resistor 34, is connected in parallel to the network termination device IO, and is supplied with power from the drop-in line 2a side. When the lid of the housing is closed and the switch 32 is in a conductive state, power supplied from the lead-in line 2a side is consumed.

Then, in the management device 24, such a network terminal device I
Monitor the power consumption of the above-mentioned series circuit section in O,
It monitors whether the network termination device IO is correctly connected to the drop-in line 2a.

Thus, according to this management form, the network termination device 10
If the lid of the casing housing the device is opened inadvertently, the switch 32 is shut off and power consumption by the series circuit section disappears, making it possible to detect an abnormality (illegal act). Also, switch 32 with the lid closed.
If the network terminating device 10 is modified and its casing is destroyed in order to interfere with the network termination device 10 while the conduction state is maintained, the casing destruction detection wiring 31 will be disconnected. The abnormality (fraud) can be detected in the same way as when opening a .

Naturally, even if an attempt is made to disconnect the lead-in line 2a and connect it to another circuit unit, an abnormality (illegality) can be detected in the same manner.

In addition, the power supply from the lead-in line 2a side to the series circuit section is as follows:
Any DC power supply or AC power supply is sufficient. Also, TDMA-S
It is also possible to use a modem, such as the interface modem 14, which is supplied with power from the center side, in place of the load resistor 35.

By taking such measures, it is possible to effectively detect the occurrence of fraud or failure in the network termination device 10 (on the subscriber premises wiring 2a side) on the center device 1 side. Accordingly, it becomes possible to take countermeasures against interference, such as promptly cutting off the upstream line from the network termination device IO. Therefore, even if sabotage is attempted, it is possible to effectively eliminate it and prevent system failure.

Note that recovery of the network terminal device 10 whose line has been blocked due to fraud detected in this way is, for example, performed by the network terminal device 1
It is only necessary to release the blockage after confirming that the failure recovery procedure has been performed according to the normal procedure from 0.

As described above about the network termination device 10 according to the present invention and the network system configured using this network termination device 10, this network system effectively solves the problem of flow noise. In addition, it is possible to effectively eliminate the problem of dynamic range. Furthermore, we can effectively deal with fraud such as interference,
The safety of the entire system can be sufficiently ensured.

It should be noted that the present invention is not limited to the two consecutive embodiments, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, the problem of flow noise in a network system can be solved by simply constructing a network system by providing it between a drop-in line and a subscriber's premises wiring. At the same time, problems regarding the dynamic range in subscriber premises wiring can also be solved. In addition, great practical effects can be achieved, such as being able to effectively deal with fraud such as interference and sufficiently ensuring the safety of the entire system.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a network configured using a network termination device according to the present invention, FIG. 2 is a schematic configuration diagram of a network termination device according to an embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the management form of the network termination device, FIG. 4 is a diagram showing an example of a case housing the network termination device, FIG. 5 is a diagram showing an example of the configuration of a series circuit section used for fraud detection, and FIG. 7 is a diagram showing an example of a broadband network, and FIG. 7 is a diagram for explaining the form of wiring within a subscriber's premises and its problems. ■...Center equipment, 2...Transmission line, 2a... Drop-in line, 2b... subscriber premises wiring, 3... terminal equipment,
5...Protector, terminal...Terminal, 9...Terminal resistor, 10
...Network termination device, lla, 11b-lln...Distribution terminal, 12...Termination resistor, 13...Coupler, 14
...TDM, A-S interface modem, 15
...Packet data modem, 16...Amplifier,
17... Frequency converter, 18... Mixer, 24...
・Management device, 31... Wiring for detecting case destruction, 32...
·switch. Applicant's agent Patent attorney Takehiko Suzue KS Figure 2;+:+': 5 Figure 7

Claims (3)

[Claims] (1) A network termination device installed between a drop-in line and a subscriber's premises wiring of a network in which a plurality of subscriber premises wiring are connected to a tree-shaped or bus-shaped transmission line via drop-in lines. a coupler comprising a plurality of distribution terminals for distributing the above-mentioned lead-in wires, and terminating empty terminals at a predetermined impedance; and one of the distribution terminals of this coupler.
a first unidirectional buffer connected to one of the distribution terminals of the coupler and transmitting some or all of the received signal from the drop line to the customer premises wiring; A network termination device comprising: a second unidirectional buffer that transmits a predetermined signal transmitted from the in-house wiring to the drop-in line. (2) a coupler, a first unidirectional buffer, and a second
2. The network termination device according to claim 1, wherein the unidirectional buffer is provided so as to be electromagnetically shielded from the outside. (3) The network terminating device according to claim 1, wherein the first and second unidirectional buffers each comprise a demodulator and a modulator of a modem.