Terminating device for installation at a termination of a power line usable for power line communication

A terminating device enables power line communication to be performed while suppressing degradation of the communication quality without decreasing the communication efficiency. The terminating device includes power supply plugs, a terminating circuit, a changeover switch, and power jack terminals, which are housed in an adapter case. The terminating circuit has an impedance corresponding to the impedance between power lines in the used frequency band of power line communication and is connected or disconnected between the power supply plugs by the changeover switch.

FIELD OF THE INVENTION

This invention relates to a terminating device for being installed at the termination of an indoor power line used for power line communication.

BACKGROUND OF THE RELATED ART

Power line communication, also known as Broadband over Power Lines (BPL), is communications using a power line such as electric wires for supplying commercial power as a transmission line and is generally performed as balanced transmission using parallel electric wires. In indoor power line communication, each communication apparatus is connected through a modem to an electric outlet to which two or three electric wires are connected. Both transmission and reception are executed between the communication apparatus connected to the electric outlet.

Since the indoor power line is not essentially laid as the transmission line, the power line is not suitable to communications in some cases. For example, if an electric apparatus is not connected to an electric outlet, the electric wires are in a state of a so-called open stub at the electric outlet and the communication quality is adversely affected. That is, because the electric outlet becomes an open end (high impedance), the input impedance characteristic of the power line to which a predetermined load is connected becomes unstable relative to the frequency. Consequently, reflection of a high frequency signal occurs, and thus a communication signal is degraded.

In a state in which a power plug of an electric apparatus is connected to an electric outlet, the input impedance of the electric apparatus is small in a high frequency and the electric wires are in a state of a so-called short stub state at the electric outlet. Consequently, reflection of a high frequency signal occurs in the portion of the electric outlet, and the communication quality deteriorates.

US2006/0214507 A1 describes terminating devices that are for being connected to an electrical outlet of an indoor power line and that have a plug for enabling an electric apparatus to be connected thereto. However, if an electric apparatus for power line communication (a modem, etc.) is connected to the terminating device, a communication signal of power line communication is absorbed in the terminating device and the communication efficiency is reduced. If a modem, etc., is connected to the electrical outlet adjoining (or close to) the electrical outlet to which the terminating device is connected, absorption of a communication signal also occurs, and a decrease in the communication efficiency cannot be avoided.

It is therefore an object of the invention to provide a terminating device for making it possible to conduct power line communication with suppression of the degradation of the communication quality without decreasing the communication efficiency.

SUMMARY

To address the above-described problems, a terminating device is installed at the termination of an indoor power line used for power line communication, which makes it possible to conduct power line communication with suppression of degradation of the communication quality without decreasing the communication efficiency.

A terminating device is installed at a termination of a power line usable for power line communication. The terminating device includes first and second terminals, a terminating circuit and a switch. The first and second terminals are capable of being connected to the power line. The terminating circuit has a predetermined impedance and is connected to the first terminal. The switch is connected to the second terminal in series with the first terminal, the terminating circuit and the second terminal and switches connection between the first and second terminals.

DETAILED DESCRIPTION

Reference will now be made in detail to the presently non-limiting, exemplary and preferred embodiments of the invention as illustrated in the accompanying drawings. The nature, concepts, objectives and advantages of the present invention will become more apparent to those skilled in the art after considering the following detailed description in connection with the accompanying drawings. The following description is provided in order to explain preferred embodiments of the present invention, with the particular features and details shown therein being by way of non-limiting illustrative examples of various embodiments of the present invention. The particular features and details are presented with the goal of providing what is believed to be the most useful and readily understood description of the principles and conceptual versions of the present invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the present invention. The detailed description considered with the appended drawings are intended to make apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

First Embodiment

Referring toFIG. 1, a terminating device is used as an adapter that can be attached to and detached from an electric outlet corresponding to the termination of an indoor power line. The terminating device includes plug terminals11aand11b, a terminating circuit12, a changeover switch13, and power jack terminals14aand14b, and is housed in an adapter case100schematically shown. A power line has a pair of electric wires such as VVF cable, etc., for example, and is laid indoors in a residence (for example, a condominium or a detached house), an office, a factory, etc.

The plug terminals11aand11bare inserted into power jacks51aand51bof an electric outlet50respectively. The power jacks51aand51bare respectively connected to one of power lines52(indoor power line). The terminating circuit12is connected to the plug terminal11b. The changeover switch13is connected to the plug terminal11ain series with the plug terminal11a, the terminating circuit12and the plug terminal11b. That is, the terminating circuit12is connected, through the changeover switch13, to the plug terminal11a.

The changeover switch13is a switch identified as SPDT (single pole, double throw) or SPCO (single pole changeover) such as a toggle switch, a membrane switch and a MOSFET, etc. The changeover switch13switches connection between the plug terminals11aand11b. That is, the changeover switch13opens or closes connection between the plug terminal11aand the terminating circuit12. The power jack terminals14aand14bare power supply terminals for supplying power to the outside, particularly to power plugs of a communication apparatus for performing power line communication and various electric apparatuses other than a communication apparatus.

The frequency band used for power line communication is MF: Medium frequency (300 k to 3 MHz), HF: High frequency (3M to 30M Hz) and VHF: Very High frequency (30M to 300M Hz). In this embodiment, the used frequency band is 1.795 to 30 MHz, but the maximum of the used frequency band may be expanded into 80 MHz.

While the changeover switch13opens connection between the plug terminal11aand the terminating circuit12, the changeover switch13closes connection between the plug terminals11a,11band the power jack terminals14a,14b. When the changeover switch13closes the connection between the plug terminal11aand the terminating circuit12, the changeover switch13opens the connection between the plug terminals11a,11band the power jack terminals14a,14b. Hereinafter, the term “communication apparatus” refers to a communication apparatus performing power line communication. Also, the term “electric apparatus” refers to various electric apparatuses other than a communication apparatus.

The terminating circuit12has predetermined impedance corresponding to the impedance between indoor power lines in the used frequency band of power line communication. A range of the predetermined impedance (absolute value) is tens to 1 k ohms, but 50 to 150 ohms is preferable. The terminating circuit12has a series circuit of an electrostatic capacitative element121and a resistance element122. That is, the terminating circuit12has the electrostatic capacitative element121and the resistance element122as circuit elements. Any circuit elements can be selected within the above-mentioned range. Therefore, the indoor power line is terminated in the terminating circuit12in a state in which the plug terminals11aand11bare inserted into the power jacks51aand51bof the electric outlet50and the terminating circuit12is connected between the plug terminals11aand11b. Accordingly, the input impedance characteristic of the power line to which a predetermined load is connected (which will be hereinafter referred to simply as “input impedance”) can be stabilized relative to the frequency, so that reflection of a high frequency signal used for power line communication can be decreased.

The terminating circuit12is not limited to the series circuit of the electrostatic capacitative element121and the resistance element122as shown inFIG. 1and may be any circuit that has the predetermined impedance. The impedance of the terminating circuit12need not be fixed and may be changeable.

Referring toFIG. 2A, the terminating circuit12has one resistance element122. Referring toFIG. 2B, the terminating circuit12has one variable resistance element122a. Referring toFIG. 2C, the terminating circuit12has one variable impedance element123. The resistance value of the variable resistance element122aand the impedance of the variable impedance element123may be manually changeable or may be electrically changeable.

Referring toFIG. 2D, either of one resistance element122and one impedance element124is selected by a termination impedance switch125. The termination impedance switch125may be manually switched by a toggle switch and a membrane switch or may be automatically switched, by appropriate drive means such as a MOSFET and a relay, in response to the use state. The termination impedance switch125may be used as the changeover switch13.

In the terminating circuit inFIG. 1, when the terminating circuit12connects between the plug terminals11aand11b, the plug terminal11aand the power jack terminal14aare disconnected. But the terminating circuit12may be disconnected from both the plug terminal11aand the power jack terminal14awithout the plug terminal11abeing disconnected from the power jack terminal14a. In this condition, if a communication apparatus is connected to the power jack terminal14a, the changeover switch13is operated so as to disconnect the terminating circuit12from the plug terminals11a,11b.

FIG. 1shows the terminating device applied to an adapter attached to and detached from the electric outlet50, but it may alternatively be applied to the electric outlet50. In this case, the terminating circuit12and the changeover switch13are connected to a feeding conductor (power line)52of the electric outlet50in a similar configuration to that shown inFIG. 11.

The terminating device of the first embodiment can also be configured as an adapter connected to a power cable of a communication apparatus. Referring toFIG. 3, the terminating device includes plug terminals11aand11b, a terminating circuit12, switches13aand13b, and a power cable connection section (power supply terminal)21, and is housed in an adapter case100schematically shown. The power cable connection section21is an electrical outlet having the power jack terminals14aand14b.

Referring toFIG. 3, the plug terminals11aand11bare respectively inserted into the power jacks51aand51bof the electric outlet50shown inFIG. 1. The power jacks51aand51bare respectively connected to one of power lines52(indoor power wiring). The terminating circuit12includes a series circuit of two capacitative elements121aand121band a resistance element112. The switches13a,13bswitch connection between the plug terminals11a,11band the terminating circuit12. A power cable20of a power line communication modem90(which will be hereinafter described as PLC modem), which is a kind of communication device, is connected to the power cable connection section21and is connected to the plug terminals11a,11bthrough the changeover switches13a,13b.

To connect the terminating device to the electrical outlet50(seeFIG. 1) and operate the PLC modem, the switches13aand13bare switched to the power cable connection section21side and the PLC modem and the power lines52(seeFIG. 1) are electrically connected through the plug terminals11aand11b, the switches13aand13b, the power cable connection section21, and the power cable20.

As the terminating circuit12, not only that shown inFIG. 3, but also any circuit containing those elements shown inFIGS. 2A,2B,2C and2D can be adopted. The configuration of the changeover switches13a,13bcan be appropriately changed to one having predetermined impedance as in the terminating device inFIG. 1. The communication apparatus can include not only a communication apparatus single unit such as a modem, but also an electric apparatus with a built-in modem.

The specific configuration and the switching operation of the switch will be discussed with reference toFIGS. 4Ato8.FIGS. 4A to 8describe the operation when a power plug91connected to a power cable92of a communication device, etc., is connected to power jack terminals14aand14bof a terminating device as shown inFIG. 1or jack terminals of an electrical outlet incorporating a terminating device. InFIGS. 4A to 8, power supply conductors101aand101bdenote conductors connected to plug terminals11aand11bof a terminating device as shown inFIG. 1or feeding conductors of an electrical outlet. SinceFIGS. 4A to 8are drawings to describe the switching operation, the configuration of the power jack is shown schematically or is omitted.

Referring toFIGS. 4A and 4B, the terminating device is provided with moving conductors13axand13bxof the switches in insertion slots of plug terminals91aand91b.

Referring toFIG. 4A, the moving conductors13ax,13bxcan rotate with one end as a supporting point. Before the plug terminals91aand91bare inserted, an electrostatic capacitative element121and a resistance element122making up the terminating circuit are connected to the power supply conductors101aand101b. Referring toFIG. 4B, when the plug terminals91aand91bare inserted, the moving conductors13axand13bxrotate, disconnecting the electrostatic capacitative element121and the resistance element from the power supply conductors101aand101b.

Referring toFIG. 5, the terminating device is of a similar structure to that inFIGS. 4A and 4Bexcept that moving conductors13axand13bxof the switches can rotate with the center as a supporting point, and when the plug terminals91aand91bare inserted, the plug terminals91aand91band power supply conductors101aand101bare connected through the moving conductors13axand13bx.

Referring toFIG. 5A, before the plug terminals91aand91bare inserted, an electrostatic capacitative element121and a resistance element122making up the terminating circuit are connected to the power supply conductors101aand101b. Referring toFIG. 5B, when the plug terminals91aand91bare inserted, the moving conductors13axand13bxrotate, disconnecting the electrostatic capacitative element121and the resistance element from the power supply conductors101aand101b, and the plug terminals91aand91band the power supply conductors101aand101bare connected.

Referring toFIGS. 6A and 6B, in the terminating device, a light emission section31and a light reception section32are placed so as to sandwich inserted plug terminals91aand91bin the proximity of insertion slots of the plug terminals91aand91b, and a changeover switch13operating in response to the state of the light reception section32is provided between an electrostatic capacitative element121and a resistance element122making up the terminating circuit and power supply conductors101aand101b. The light emission section31may be, for example, a light emitting diode, etc., and the light reception section32may be for example, a silicon diode, a photo transistor, etc.

Referring toFIG. 6A, before the plug terminals91aand91bare inserted, light from the light emission section31is incident on the light reception section32and thus an electrostatic capacitative element121and a resistance element122are connected to the power supply conductors101aand101b. Referring toFIG. 6B, when the plug terminals91aand91bare inserted, the light from the light emission section31is blocked, and thus no light is incident on the light reception section32. Consequently, the changeover switch13is turned off, disconnecting the electrostatic capacitative element121and the resistance element122from the power supply conductors101aand101b.

Referring toFIGS. 7A and 7B, the terminating device has a similar structure to that inFIGS. 6A and 6Bexcept that a light emission section31and a light reception section32are placed on one side in the proximity of insertion slots of the plug terminals91aand91b.

Referring toFIG. 7A, before the plug terminals91aand91bare inserted, light from the light emission section31is not incident on the light reception section32. At this time, a setting is made so that the changeover switch13is turned on unlike that inFIG. 6, and an electrostatic capacitative element121and a resistance element122are connected to power supply conductors101aand101b.

Referring toFIG. 7B, when the plug terminals91aand91bare inserted, the light from the light emission section31is reflected on the plug terminal91aand is incident on the light reception section32, and thus the changeover switch13is turned off, disconnecting the electrostatic capacitative element121and the resistance element122from the power supply conductors101aand101b.

Referring toFIGS. 8A and 8Bin the terminating device, a push switch33pushed by the inserted plug terminal91a(or91b) is placed in the proximity of insertion slots of the plug terminals91aand91b, and a relay34controlled in response to the state of the push switch33is provided between an electrostatic capacitative element121and a resistance element122making up the terminating circuit and power supply conductors101aand101b.

Referring toFIG. 8A, before the plug terminals91aand91bare inserted, the push switch33is off and the relay34is on, connecting the electrostatic capacitative element121and the resistance element122to the power supply conductors101aand101b.

Referring toFIG. 8B, when the plug terminals91aand91bare inserted, the push switch33is turned on and thus the relay34is turned off, disconnecting the electrostatic capacitative element121and the resistance element122from the power supply conductors101aand101b.

In this embodiment, the changeover switch may switch the connection in accordance with the operation status of the communication apparatus. The operation status includes power ON/OFF and operation mode such as stand-by (sleep mode) or active mode (power ON).

Second Embodiment

Referring toFIG. 9, the terminating device is used as an adapter that can be attached to and detached from an electric outlet of an indoor power line like the terminating device inFIG. 1. The terminating device includes plug terminals11aand11b, a terminating circuit12, a changeover switch131, power jack terminals14aand14b, an impedance section15, and short-circuit switches16aand16b, and is housed in an adapter case100schematically shown.

The plug terminals11aand11bare inserted into power jacks51aand51bof an electric outlet50shown inFIG. 1. The power jacks51aand51bare respectively connected to one of power lines52. The terminating circuit12connects, through the changeover switch131, the plug terminal11ato and the plug terminal11b.

The changeover switch131switches connection between the plug terminal11aand the terminating circuit12. The power jack terminals14aand14bare provided for supplying power to the outside and transmitting a signal to power plugs of a communication apparatus and various electric apparatuses.

The terminating circuit12has impedance corresponding to the impedance between indoor power lines in the used frequency band of power line communication. The terminating circuit12has a series circuit of an electrostatic capacitative element121and a resistance element122. Therefore, the indoor power line is terminated in the electrical outlet in a state in which the terminating circuit12connects the plug terminal11ato the plug terminal11b. Consequently, reflection of a high frequency signal used for power line communication can be decreased.

As the terminating circuit12, not only that shown inFIG. 9, but also any circuit containing a structure as shown inFIGS. 2A,2B,2C and2D can be adopted, as with the terminating device of the first embodiment.

The impedance section15has a high impedance in the used frequency band of power line communications and is an inductance element, for example. A range of the high impedance (absolute value) is hundreds and more ohms, but 1 k and more ohms are preferable. The impedance section15is inserted between lines for connecting the plug terminals11a,11bto the power jack terminals14a,14bon the side of the power jack terminals14aand14b(on the opposite side to the feeding side of power line) from the connection part of the terminating circuit12. In the terminating device shown inFIG. 9, the inductance element is inserted in both lines for connecting the plug terminals11a,11bto the power jack terminals14a,14b, but may be inserted only in either one of them.

If a low-impedance electric apparatus such as a re-charger is connected to the side of the power jack terminals14aand14b, the impedance section15is inserted, so that the impedance becomes high in the used frequency band of power line communication. Therefore, the effect of the impedance of the electric machine on power line communication can be suppressed. Further, a suppression function of noise occurring from an electric apparatus is also provided, so that the S/N ratio of power line communication can be improved.

The short-circuit switches16aand16bshort-circuit the impedance section15inserted between the plug terminals11aand11band the power jack terminals14aand14b. The short-circuit switches16aand16boperate in conjunction with the changeover switch131. That is, if the changeover switch131is turned off and the terminating circuit12is disconnected from the plug terminals11aand11b, the impedance section15is short-circuited by the short-circuit switches16aand16b.

This state is set if a communication apparatus is connected to the power jack terminals14aand14b. Therefore, if the impedance section15is short-circuited, the terminating circuit12is disconnected from the plug terminals11aand11b. Thus, the input impedance can be stabilized, so that the communication apparatus can reduce both attenuation of a communication signal by the impedance section15and absorption of a communication signal by inserting the terminating circuit12. As a result, the communication apparatus can conduct efficient communications.

Thus, the terminating device shown inFIG. 9enables the power jack terminals11aand11bto be used in an efficient state for a communication apparatus and for an electric apparatus.

Referring toFIG. 10, the terminating device has a similar configuration to that of the terminating device inFIG. 9except that they differ in configurations of changeover switch132and short-circuit switches161aand161b.

In the terminating device ofFIG. 10, the short-circuit switch161band the changeover switch132are integrated into one structure and are operated in conjunction with each other. That is, if the short-circuit switch161bis turned counterclockwise, the terminating circuit12connects the power jack terminal11ato the power jack terminal11band the impedance section15is inserted between the power jack terminal11band the power jack terminal14b. If the short-circuit switch161bis turned clockwise, the terminating circuit12is disconnected and the impedance section15is short-circuited. Therefore, the conjunctive operation of the changeover switch132and the short-circuit switches161aand161bis simplified.

Referring toFIG. 11, the terminating device has a similar configuration to that of the terminating device ofFIG. 10except that it is in an electrical outlet. The terminating circuit12, the changeover switch132, the power jack terminals14aand14b, the impedance section15, and the short-circuit switches161aand161bare housed in an outlet case200(schematically shown in the figure) attached to a wall25. A conductor connected to the power jack terminals11aand11binFIG. 10is connected to a feeding conductor of the electric outlet.

The operation or use method of the terminating device inFIG. 11is the same as that of the terminating device inFIG. 10. Therefore, the operation will not be described again. InFIG. 11, electric wires making up indoor power line are not shown.

Referring toFIG. 12, the terminating device has a similar configuration to that of the terminating device inFIG. 10or the terminating device inFIG. 10except that a connection type detection section17for detecting the type of inserted power plug is provided in the proximity of the power jack terminals14aand14band the changeover switch132, and the short-circuit switches161aand161bare switched in response to the detection result of the connection type detection section17.

The connection type detection section17detects whether the power plug connected to the power jack terminals14aand14bis that for a communication apparatus or that for an electric apparatus other than the communication apparatus. This detection can be made mechanically or electrically. To make the detection mechanically, the shape of a power plug of a communication apparatus is made different from that of a usual power plug of an electric apparatus (for example, a projection is provided). Whether or not a communication apparatus is connected is determined by a switch responsive to the shape. To make the detection electrically, the frequency of a signal flowing into the conductor from the power jack terminals14aand14bis determined. If a high frequency signal used for communications is detected, it is determined that a communication apparatus is connected.

If it is determined that a communication apparatus is connected, the impedance section15is short-circuited by the short-circuit switches161aand161b, and the terminating circuit12is disconnected by the changeover switch132.

Third Embodiment

Referring toFIG. 13, the terminating device is used as an adapter that can be attached to and detached from an electric outlet of an indoor power line like the terminating device inFIG. 1,FIG. 9, andFIG. 10. The terminating device includes plug terminals11aand11b, a terminating circuit12, a changeover switch13, power jack terminals (first power supply terminals)14aand14b, an impedance section15, and power jack terminals (second power supply terminals)18aand18b, and is housed in an adapter case100schematically shown.

The plug terminals11aand11bare inserted into power jacks51aand51bof an electric outlet50shown inFIG. 1and are respectively connected to one of power lines52. The terminating circuit12is connected, through the changeover switch13, the plug terminal11aand to the plug terminal11b.

The changeover switch13switches connection of the terminating circuit12. If the changeover switch13connects the terminating circuit12between the plug terminals11aand11b, connection between the plug terminal11aand the power jack terminal18ais disconnected. The power jack terminals14aand14bare provided for supplying power to the outside and transmitting a signal to power plugs of a communication apparatus and an electric apparatus.

The terminating circuit12has an impedance corresponding to the impedance between indoor power lines in the used frequency band of power line communication. The terminating circuit12has a series circuit of an electrostatic capacitative element121and a resistance element122. Therefore, the indoor power line is terminated in the electric outlet in a state in which the terminating circuit12connects the plug terminal11ato the plug terminal11b. As a result, reflection of a high frequency signal used for power line communication can be decreased.

As the terminating circuit12, not only that shown inFIG. 13, but also any configuration shown inFIGS. 2A,2B,2C and2D can be adopted, as with the terminating device of the first embodiment.

The impedance section15has a high impedance in the used frequency band of power line communication and is an inductance element, for example. The impedance section15is inserted between lines for connecting the plug terminals11a,11bto the power jack terminals14a,14bon the side of the power jack terminals14aand14b(on the opposite side to the feeding side of power line) from the connection part of the terminating circuit12. In the terminating device inFIG. 13, the inductance element is inserted in both lines for connecting the plug terminals11aand11band the power jack terminals14aand14b, but may be inserted only in either one of them.

If a low-impedance electric apparatus such as a re-charger is connected to the side of the power jack terminals14aand14b, the impedance section15is inserted, so that the impedance becomes high in the used frequency band of power line communication. Therefore, the effect of the impedance of the electric machine on power line communication can be suppressed. Further, a suppression function of noise occurring from an electric machine is also provided, so that the S/N ratio of power line communication can be improved.

The power jack terminals18aand18bare connected to the plug terminals11aand11bthrough the changeover switch13. A power plug of a communication apparatus is connected to the power jack terminals18aand18b. When a power plug of a communication apparatus is connected (preferably, when power of a communication apparatus is turned on), the changeover switch13connects the plug terminal11ato the power jack terminal18a.

Thus, the terminating device ofFIG. 13includes the power jack terminals (power supply terminals) having different functions, so that both a communication apparatus and an electric apparatus other than the communication apparatus can be connected. When a communication apparatus is connected and power line communications are conducted, power is also supplied to an electric apparatus through the impedance section15, so that the effect of the impedance of the electric apparatus on power line communication can be suppressed and S/N of power line communication can also be improved. A communication apparatus is connected to a power line not through the impedance section15and the terminating circuit12is also disconnected from the plug terminals11a,11b, so that attenuation of a communication signal by the impedance section15is reduced and absorption of a communication signal by inserting the terminating circuit12is reduced. As a result, efficient communications are made possible.

Referring toFIG. 14, the terminating device has a somewhat similar configuration to that of the terminating device inFIG. 13except that it is incorporated in an electrical outlet, and the terminating circuit12, the changeover switch13, the power jack terminals14aand14b, the impedance section15, and the power jack terminals18aand18bare housed in an outlet case200(schematically shown in the figure) attached to a wall25. A conductor connected to the power jack terminals11aand11binFIG. 13is connected to a feeding conductor of the electric outlet.

The operation or use method of the terminating device inFIG. 14is the same as that of the terminating device inFIG. 13and therefore will not be described again.

Referring toFIG. 15, the terminating device is a terminating device wherein the components included in the terminating device inFIG. 13are housed in two cases. These cases are connected by a power cable.

The terminating device inFIG. 15includes the plug terminals11aand11b, the terminating circuit12, the changeover switch13, and the power jack terminals18aand18b, which are housed in an adapter case100schematically shown in the figure. It also includes the impedance section15and outlet connection ports19a,19b,19c, and19d, which are housed in an outlet tap case300schematically shown in the figure. The adapter case100is provided with a power cable connection section21connected to the plug terminals11aand11b, and the outlet tap case300is provided with a power cable connection section22connected to the outlet connection ports19a,19b,19c, and19dthrough the impedance section15. The power cable connection section21is connected, through a power cable20, to the power cable connection section22.

The plug terminals11aand11b, the terminating circuit12, the changeover switch13, and the power jack terminals18aand18bare similar to those of the terminating device inFIG. 13, and a communication apparatus is connected to the power jack terminals18aand18b. The impedance section15is also similar to that of the terminating device inFIG. 13, and if a low-impedance electric machine is connected to the outlet connection port19a,19b,19c, or19d, as the impedance section15is inserted, the impedance becomes high in the used frequency band of power line communications and thus the effect of the impedance of the electric machine on power line communication can be suppressed. Further, a suppression function of noise occurring from an electric machine is also provided, so that the S/N ratio of power line communications can be improved.

As is apparent from the description given above, the operation or use method of the terminating device inFIG. 15is the same as that of the terminating device inFIG. 13and therefore will not be described again.

Referring toFIG. 16, the terminating device is a terminating device wherein the components included in the terminating device inFIG. 13are housed in two cases. These cases are connected by a power cable.

The terminating device inFIG. 16includes the terminating circuit12, the changeover switch13, the impedance section15, and the outlet connection ports19a,19b,19c, and19d, which are housed in an outlet tap case400schematically shown in the figure. It is also provided with a plug case11cfor housing the plug terminals11aand11b. The plug case11cis connected, by a power cable20, to the outlet tap case400. The power cable20is connected to both ends of the terminating circuit12through the changeover switch13and further is connected to an outlet connection port18. It is also connected to the outlet connection port19a,19b,19c,19dthrough the impedance section15.

In the terminating device inFIG. 16, as the terminating circuit12, a configuration for switching a plurality of impedance elements for connection as shown inFIG. 2Dis shown, but a similar one to that shown inFIG. 15may be adopted.

In the terminating device inFIG. 16, like the terminating device inFIG. 15, the outlet connection ports19a,19b,19c, and19dare used for low-impedance electric machines. The outlet connection port18is used for a communication apparatus. As is apparent from the description given above, the operation or use method of the terminating device inFIG. 16is the same as that of the terminating device inFIG. 13and therefore will not be discussed again.

Referring toFIG. 17, the terminating device includes the plug terminals11aand11b, the terminating circuit12, the changeover switch131, the impedance section15, the tap connection ports19a,19b,19c, and19d, and short-circuit switches19aa,19ba,19ca,19da,19ab,19bb,19cd, and19db.

The plug terminals11aand11b, the terminating circuit12, and the changeover switch13are housed in an adapter case100schematically shown in the figure, and the impedance section15, the tap connection ports19a,19b,19c, and19d, and the short-circuit switches19aa,19ba,19ca,19da,19ab,19bb,19cd, and19dbare housed in an outlet tap case500schematically shown in the figure. The adapter case100and the outlet tap case500are connected through a power cable20. The power cable20is connected to the plug terminals11aand11bin the adapter case100and is connected to the tap connection ports19a,19b,19c, and19dthrough the power cable connection section22, the impedance section15, and the short-circuit switches19aa,19ba,19ca,19da,19ab,19bb,19cd, and19dbprovided in the outlet tap case500. It is connected to the tap connection ports19a,19b,19c, and19dthrough the short-circuit switches19aa,19ba,19ca,19da,19ab,19bb,19cd, and19dbdirectly from the power cable connection section22.

The short-circuit switches19aa,19ba,19ca,19da,19ab,19bb,19cd, and19dbswitch between insertion and short circuit of the impedance section15and the short-circuit switch, corresponding to the tap connection port to which a communication apparatus is connected, switches so as to short-circuit the impedance section15. When a communication apparatus is connected to any of the tap connection port19a,19b,19c, or19d, the switch3switches so as to disconnect the terminating circuit12.

As switching is thus performed, the S/N ratio of power line communication can be improved, and efficient communications are made possible regardless of whether a communication apparatus or an electric machine other than the communication apparatus is connected to any of the tap connection port19a,19b,19c, or19d.

FIG. 18shows the schematic configuration of still another example of the terminating device of the third embodiment of the invention. The terminating device inFIG. 18is configured as an adapter connected to a power cable of a communication apparatus for conducting power line communication.

The terminating device shown inFIG. 18includes the plug terminals11aand11b, the terminating circuit12, the changeover switch13, the power jack terminals (first power supply terminals)14aand14b, the impedance section15, and the power cable connection section (second power supply terminals)21, and is housed in an adapter case100schematically shown. A power cable20of a PLC modem90is connected to the power cable connection section21and is connected to the plug terminals11aand11bthrough switches13aand13b.

As is apparent fromFIG. 18, the terminating device inFIG. 18can operate and be used as the power cable20of the PLC modem90is connected to the power jack terminals18aand18bin the terminating device inFIG. 13. That is, an electric machine other than a communication apparatus is connected to the power jack terminals14aand14b, and when the PLC modem90is used, the changeover switch13is connected to the power cable connection section21and the terminating circuit12is disconnected.

FIG. 19is a block diagram to show a hardware example of the PLC modem inFIG. 13andFIG. 18. The PLC modem90has a case900(dashed line) and the case900is provided with a power connector71and a LAN (local area network) modular jack72of RJ45, etc. A power cable20as an example of a power line is connected to the power connector71. A LAN cable600is connected to the modular jack72. The PLC modem90contains a switching power supply60and a circuit module70. The switching power supply60supplies various (for example, +1.2 V, +3.3 V, and +12 V) voltages to the circuit module70. The circuit module70is provided with a main IC73, an AFC IC (Analog Front End IC)75, a low-pass filter76, a driver IC77, a coupler79, a band-pass filter80, memory81, and Ethernet PHY IC82.

The main IC73is made up of a CPU (Central Processing Unit)73A, a PLC MAC (Power Line Communication Media Access Control layer) block73C, and a PLC PHY (Power Line Communication Physical layer) block73B. A 32-bit RISC (reduced instruction set computer) processor is installed in the CPU73A. The PLC MAC block73C manages a MAC layer of a transmission signal and the PLC PHY block73B manages a PHY layer of a transmission signal. The AFE IC75is made up of a DA converter (DAC)75A, an AD converter (ADC)75B, and variable amplifiers (VGA)75C and75D. The coupler79is made up of a coil transformer79A and coupling capacitors79B and79C.

The foregoing description illustrates and describes the present invention. However, the disclosure shows and describes only the preferred embodiments of the invention, but it is to be understood that the invention is capable of use in various other combinations, modifications, and environments. Also, the invention is capable of change or modification, within the scope of the inventive concept, as expressed herein, that is commensurate with the above teachings and the skill or knowledge of one skilled in the relevant art. For example, one or more elements of each embodiment may be omitted or incorporated into the other embodiments.

The foregoing description of implementations and embodiments of the invention have been presented for purposes of non-limiting illustration and description. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particular features and details disclosed herein. Rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. The descriptions provided herein are not exhaustive and do not limit the invention to the precise forms disclosed. The foregoing embodiment examples have been provided merely for purposes of explanation and are in no way to be construed as limiting the scope of the present invention. The words that have been used herein are words of description and illustration, rather than words of limitation. The present teachings can readily be realized and applied to other types of apparatuses. Further, modifications and variations, within the purview, scope and spirit of the appended claims and their equivalents, as presently stated and as amended hereafter, are possible in light of the above teachings or may be acquired from practicing the invention. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated Alternative structures discussed for the purpose of highlighting the invention's advantages do not constitute prior art unless expressly so identified. No one or more features of the present invention are necessary or critical unless otherwise specified.

The present application is based on Japanese Patent Application No. 2005-311402 filed on Oct. 26, 2005, which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The invention is useful as a terminating device, etc., for making it possible to conduct power line communication with degradation of the communication quality suppressed without decreasing the communication efficiency.