Abstract:
Provided is a plug socket which determines operation states of a plurality of electrical devices connected to the plug socket to supply or cut off electric power to the electrical devices and selects a method for supplying or cutting off electric power to the electrical devices by setting a desired mode. Thus, it is possible to prevent the waste of energy and electrical accidents by cutting off the electric power when the electrical devices connected to the plug socket are not used. Especially, since the electric power is supplied only when the electrical devices are used in a home network system, it is possible to efficiently use electricity, significantly reduce unnecessary power consumption, and thus the cost is reduced. Moreover, in the case of a built-in plug socket, it is possible to change the time or method for cutting off electric power by setting a desired mode according to the kind of the electrical device, and thus user convenience is significantly improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2008-0019163, filed on Feb.29, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Further, this application is the National Phase application of International Application No. PCT/KR2009/000938, filed Feb. 27, 2009, which designates the United States and was published in Korean. This application, in its entirety, is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a plug socket and, more particularly, to a plug socket which automatically cuts off electric power supplied to a connected electrical device in response to a load current of the connected electrical device and changes a power control method for each operation mode. 
         [0004]    2. Discussion of Related Art 
         [0005]    In general, since electrical appliances used at home, such as TV sets, computers, microwave ovens, audio systems, etc., are used frequently, their plugs often remain plugged into a socket even when the electrical appliances are not in use for a long time. 
         [0006]    These electrical appliances consume a certain amount of standby power even when not in use, and thus electric power is unnecessarily consumed. In order to prevent standby power consumption, the plug should be removed from the socket so that electric power is not supplied to the electrical appliances connected to the socket. However, it can be troublesome to insert and remove the plug into and from the socket each time the appliance is used. 
         [0007]    Therefore, a plug socket with a switch for supplying or cutting off electric power to the electrical appliances connected to the plug socket is widely used. 
         [0008]    However, it is still inconvenient to use the above plug socket since a user must operate the switch whenever he or she uses any of the corresponding electrical appliances connected to the plug socket. Moreover, when at least one electrical appliance is connected to the plug socket, the plug socket is generally hidden, and thus it is very inconvenient to operate the switch. 
         [0009]    In order to solve the above problems, an automatic power-saving multi-plug socket has been developed. However, it is also problematic in that the use of products to be used or applied is limited and it is difficult to install the plug socket on a wall surface and to conveniently save electric power in accordance with a variety of electrical appliances. 
         [0010]    Moreover, since it is expected that the power waste due to communication standby power between electrical appliances in a home network system will occupy more than 20% of the home&#39;s power consumption, a plan for solving this problem is urgently required. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to a plug socket which detects a load current of electric power supplied to an electrical device to determine an operation state of the electrical device, so that electric power is supplied to the electrical device or cut off. With a single plug socket of the present invention, it is possible to freely select a method for supplying or cutting off electric power to the electrical device by setting a desired mode regardless of a kind or combination of electrical devices. Thus, it is possible to prevent the waste of standby power which occupies more than 10% of a home&#39;s power consumption, improve user convenience by preventing electrical accidents and increasing the durability of the electrical devices, and save energy in a home network system. 
         [0012]    According to an aspect of the present invention, there is provided a plug socket including a power-saving circuit supplying or cutting off electric power to a connected electrical device according to a load current; a mode setting unit setting any one of an automatic mode, a manual mode, and an optional automatic mode such that the power-saving circuit is operated in the set mode; a signal input unit connected to a jack connection unit and configured to input an operation signal to supply or cut off electric power to the power-saving circuit; and a changeover switch unit including a button or a lever to forcibly supply or cut off electric power. Here, the power-saving circuit includes a switch unit switching the input electric power so that the input electric power is supplied or cut off to the electrical device and cutting off the power supply when the signal input unit is disconnected from the jack connection unit; a load current detection unit detecting a load current according to an operation state of the electrical device and inputting a load signal; and a control unit controlling the operation of the switch unit in response to at least one of the mode set by the mode setting unit, the load signal, and the operation signal of the signal input unit. 
         [0013]    According to another aspect of the present invention, there is provided a plug socket including an adaptor type socket main body in which a power-saving circuit is mounted to cut off electric power supplied to a connected electrical device; a first connection unit including a first connector connected to one side of the socket main body and a second connector having a shape different from that of the first connector and supplying external power to the socket main body; a connection plug detachably connected to the socket main body; and a signal input unit inputting an operation signal to the socket main body to supply or cut off electric power to the electrical device. 
         [0014]    According to still another aspect of the present invention, there is provided a plug socket including: a built-in type socket main body in which a power-saving circuit is mounted to cut off electric power supplied to a connected electrical device; a first power connection portion provided on a rear surface of the socket main body and connecting external power to the power-saving circuit such that electric power is supplied to the power-saving circuit; a second power connection portion connecting the power-saving circuit to external power; and a power-line disconnecting and fixing portion fixing a power line inserted into the first power connection portion and the second power connection portion in a first state and opening the first power connection portion and the second power connection portion such that the power line inserted and fixed to the first power connection portion and the second power connection portion is separated in a second state 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0016]      FIG. 1  is a perspective view showing a plug socket in accordance with a first embodiment of the present invention; 
           [0017]      FIGS. 2A and 2B  are perspective views showing a socket main body of  FIG. 1 ; 
           [0018]      FIGS. 3A and 3B  are perspective views showing a plug socket in accordance with a second embodiment of the present invention; 
           [0019]      FIG. 4  is an exploded perspective view showing the plug socket of  FIG. 3 ; 
           [0020]      FIG. 5A  is a front view of the plug socket of  FIG. 3 ; 
           [0021]      FIG. 5B  is a side view of the plug socket of  FIG. 3 ; 
           [0022]      FIG. 5C  is a rear view of the plug socket of  FIG. 3 ; 
           [0023]      FIG. 6  is a diagram showing a mode setting unit of the plug socket of  FIG. 3 ; 
           [0024]      FIG. 7  is a perspective view showing a first signal input unit connected to the plug socket of  FIG. 3 ; 
           [0025]      FIG. 8  is a perspective view showing a second signal input unit connected to the plug socket of  FIG. 3 ; 
           [0026]      FIG. 9  is a block diagram showing a configuration of the plug socket of  FIGS. 1 and 3 ; 
           [0027]      FIG. 10  is a block diagram showing a configuration of the first signal input unit of  FIG. 7 ; 
           [0028]      FIG. 11  is a block diagram showing a configuration of the second signal input unit of  FIG. 8 ; 
           [0029]      FIGS. 12A and 12B  are diagrams showing examples of use of the plug socket of  FIGS. 1 and 3 ; 
           [0030]      FIG. 13  is a flowchart showing a mode setting method of the plug socket of  FIGS. 1 and 3 ; 
           [0031]      FIG. 14  is a flowchart showing an operation in an automatic mode of the plug socket of  FIGS. 1 and 3 ; 
           [0032]      FIG. 15  is a flowchart showing an operation in an optional automatic mode of the plug socket of  FIGS. 1 and 3 ; 
           [0033]      FIG. 16  is a flowchart showing an operation in a manual/timer mode of the plug socket of  FIGS. 1 and 3 ; 
           [0034]      FIG. 17  is a flowchart showing an operation of the second signal input unit connected to the plug socket of  FIGS. 1 and 3 ; 
           [0035]      FIG. 18  is a perspective view showing a configuration of a changeover switch unit provided in the plug socket of  FIGS. 1 and 3 ; and 
           [0036]      FIGS. 19A and 19B  are perspective views showing a detailed configuration of a switch unit provided in the plug socket of  FIGS. 1 and 3 . 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0037]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present invention with reference to the figures. 
         [0038]      FIG. 1  is a perspective view showing a plug socket in accordance with a first embodiment of the present invention. 
         [0039]    The plug socket in accordance with the first embodiment of the present invention is an adaptor type plug socket which is connected to any other plug socket or a connection cable to receive electric power or connected to an electrical device to supply or cut off electric power to the connected electrical device. 
         [0040]    The plug socket includes a socket main body  10  supplying or cutting off electric power to the electrical device or any other plug socket connected to the plug socket, a first signal input unit  40  and a second signal input unit  50  inputting a predetermined signal relating to the power supply or power cut-off to the socket main body  10 . In this case, each of the first and second signal input units  40  and  50  includes a connection plug in the form of an earphone jack and is connected to the socket main body  10 . 
         [0041]    The plug socket further includes a connection cable  20  connecting the plug socket to electric power such that the electric power is supplied to the socket main body  10 , and a socket cable  30  supplying electric power output from the socket main body  10  to the electrical device. Here, a plug  21  of the connection cable  20  and a socket connection unit  31  of the socket cable  30  may have different shapes and forms, which are not limited to those shown in  FIG. 1 . 
         [0042]    Since the plugs and the plug sockets used in different countries have different shapes, the socket main body  10  is used in common, and the connection cable  20  and the socket cable  30  connected to the socket main body  10  may be modified according to the country in which they are used. However, each of connectors  22  and  32  of the connection cable  20  and the socket cable  30  has a form suitable for the socket main body  10  and, when a connector of an electrical device has a form suitable for the socket main body  10 , the connector of the electrical device can be directly connected to the socket main body  10  without the socket cable  30 . 
         [0043]    Accordingly, the socket main body may be used in common, removing a necessity to manufacture the socket main bodies separately for respective countries, and only the connection cable  20  and the socket cable  30  may be modified. Thus, it is possible to reduce waste due to design modification for each country and use the product in common. 
         [0044]      FIG. 2A  is a left side perspective view showing the socket main body of  FIG. 1 , and  FIG. 2B  is a right side perspective view thereof. 
         [0045]    As shown in  FIGS. 2A and 2B , the socket main body  10  includes a power output unit  15  supplying input power to an electrical device or any other plug socket, a power input unit  12  receiving electric power, and a socket housing  1  in which a power-saving circuit for supplying or cutting off electric power according to an operation state of the electrical device or any other plug socket when the electric power input from the power input unit  12  is output through the power output unit  15  is mounted and protected. The power output unit  15  is connected to the socket cable  30 , and the power input unit  12  is connected to the connection cable  20 . In this case, the shapes and forms of the power output unit  15  and the power input unit  12  comply with IEC 320 C13 or IEC 320 C   14   standard, but may be modified, if necessary. Moreover, the socket main body  10  includes a mode setting unit  13  and a jack connection unit  14  provided on one of upper, lower, left, and right sides of a first insertion unit  11 . 
         [0046]    The mode setting unit  13  sets a plurality of modes such that a standby time for the power supply or cut-off, a set value, a timer, or a manual cut-off is changed according to a selected mode when power is automatically cut off or supplied by the power-saving circuit. 
         [0047]    The jack connection unit  14  is provided in the socket main body  10  such that the first signal input unit  40  or the second signal input unit  50  is detachably connected. The jack connection unit  14  receives a signal from the first signal input unit  40  or the second signal input unit  50  and applies the received signal to the power-saving circuit. 
         [0048]    Moreover, the jack connection unit  14  determines whether the first signal input unit  40  or the second signal input unit  50  is connected thereto and, when the first signal input unit  40  or the second signal input unit  50  is disconnected therefrom, applies a detection signal to the power-saving circuit such that the socket main body  10  is switched to a normal power-off mode. 
         [0049]      FIGS. 3A and 3B  are perspective views showing a plug socket in accordance with a second embodiment of the present invention. 
         [0050]    As shown in  FIGS. 3A and 3B , the plug socket in accordance with the second embodiment of the present invention is a built-in type plug socket  100   a,    100   b.    
         [0051]    The plug socket  100   a,    100   b  includes at least one power-plug insertion hole  110   a,    110   b  provided on the front surface such that at least one electrical device or any other plug socket is connected thereto. A power-saving circuit is mounted on the rear surface of the power-plug insertion hole  110   a,    110   b  to supply or cut off electric power to the electrical device or any other plug socket connected to the power-plug insertion hole  110   a,    110   b.  The power-plug insertion hole  110   a,    110   b  of the plug socket  100   a,    110   b  is connected to the power-saving circuit and, when a plurality of power-plug insertion holes are provided, each of the plurality of power-plug insertion holes is connected to the same power-saving circuit. 
         [0052]    The power-saving circuit is the same as the power-saving circuit mounted on the socket main body  10  described in the first embodiment. However, since the positions and shapes of the power output unit  15  and the power input unit  12  of the socket main body  10  are different from those of the power-plug insertion hole  110   a ,  110   b,  the wiring structures with the power-saving circuit may be slightly different. However, the basic circuit configuration and function are the same. 
         [0053]    Here,  FIG. 3A  shows an example in which three power-plug insertion holes  110   a  are provided, and  FIG. 3B  shows an example in which a single power-plug insertion hole  110   b  is provided. 
         [0054]    Moreover, the power socket  100   a,    100   b  includes a jack connection unit  140   a ,  140   b  in which a signal input unit  200  is inserted and mounted. As shown in  FIGS. 3A and 3B , the jack connection unit  140   a,    140   b  may be provided on one of upper, lower, left, and right sides of the power-plug insertion hole  110   a,    110   b.    
         [0055]    When the signal input unit  200  is connected to the jack connection unit  140   a ,  140   b,  the jack connection unit  140   a,    140   b  receives a predetermined signal associated with the power supply or power cut-off from the signal input unit  200 . When the signal input unit  200  is connected or disconnected, the jack connection unit  140   a ,  140   b  detects the connection state and applies a detection state signal to the power-saving circuit. When the signal input unit  200  is disconnected from the jack connection unit  140   a,    140   b,  the power-saving circuit of the power socket  100   a,    100   b  is switched to a normal power-off mode. 
         [0056]    The first signal input unit  40  and the second signal input unit  50  described in the first embodiment may be used as the signal input unit  200 . That is, the first signal input unit  40  or the second signal input unit  50  may be connected to the jack connection unit  140   a,    140   b  of the plug socket  100   a,    100   b.    
         [0057]    The power socket  100   a,    100   b  may further include a state output unit (not shown) which displays the operation state of the power-saving circuit or is turned on and off according to the cut-off state of electric power supplied to the connected electrical device or any other power socket. 
         [0058]    When the plurality of power-plug insertion holes  110   a  are provided as shown in  FIG. 3A , a normal power-on plug insertion hole, which is not connected to the power-saving circuit, may be further provided, if necessary. In this case, it is preferable that the normal power-on plug insertion hole have a color, pattern, or shape different from the plug insertion hole connected to the power-saving circuit. 
         [0059]      FIG. 4  is an exploded perspective view showing the plug socket of  FIG. 3 . 
         [0060]    The plug socket  100   a  includes a front surface portion  101   a,  a socket assembly  102   a  in which the front surface portion  101   a  is inserted and mounted, and a main body portion  103   a  in which the power-saving circuit is mounted. The socket assembly  102   a  and the main body portion  103   a  are detachably connected to each other. 
         [0061]    The front surface portion  101   a  includes power plug holes  111   a  through which the plug is inserted and mounted to the power-plug insertion hole  110   a.  The power plug holes  111   a  correspond in number to the power-plug insertion holes. Moreover, the front surface portion  101   a  includes an insertion hole  141   a  provided on one side of the power plug hole  111   a  such that the signal input unit  200  is inserted and mounted to the jack connection unit  140   a.    
         [0062]    The insertion hole  141  a has a circular shape such that the connection plug in the form of an earphone jack is inserted. However, the shape of insertion hole  141   a  may depend on the shape of the connection jack of the signal input unit  200 . 
         [0063]    The socket assembly  102   a  includes at least one power plug mounting portion  112   a  having such a structure that the plug passing through the power plug hole  111   a  can be inserted and mounted, and a jack mounting portion  142   a  in which the connection plug of the signal input unit  200  passing through the insertion hole  141   a  is inserted and mounted. 
         [0064]    Moreover, the socket assembly  102   a  includes a mode setting unit  130  provided on one of upper, lower, left, and right sides of the jack mounting portion  142   a.  In this case, the mode setting unit  130  has the same configuration and function as the mode setting unit  13  described in the first embodiment. 
         [0065]    The mode setting unit  130  is not exposed to the outside when the front surface portion  101   a  is mounted on the socket assembly  102   a  but is exposed when the front surface portion  101   a  is detached and the socket assembly  102   a  is exposed such that a user may operate the mode setting unit  130 . 
         [0066]    The main body portion  103   a  is located on the rear surface of the socket assembly  102   a  and includes a circuit board on which the power-saving circuit is mounted. The main body portion  103   a  is inserted into or connected to the socket assembly  102   a.    
         [0067]    The insertion hole  141   a,  the jack mounting portion  142   a,  and the jack connection unit  14 ,  140   a  are aligned at the same position so that the signal input unit  200  can be connected, and the jack connection unit  14 ,  140   a  is connected to the circuit board inside the main body portion  103   a.    
         [0068]    The socket assembly may further include a changeover switch unit (not shown) provided on one of upper, lower, left, and right sides of the plug mounting portion  112   a  to be manually operated such that the plug socket  100   a  is switched to a normal power-on or power-saving mode. The changeover switch unit is connected to the main body portion  103   a  to supply electric power to a power output terminal according to the operation state. 
         [0069]    Here, the changeover switch unit, which switches the plug socket to a normal power-off or power-saving mode, may further include a push button or a lever manually operated to forcibly switch the power supply state according to whether the signal input unit  200  is mounted on or disconnected from the jack connection unit  14 ,  140   a.    
         [0070]    When the signal input unit  200  is connected and the changeover switch unit is set to a power saving mode, the plug socket  100   a  supplies the input power to the electrical device or any other plug socket connected to the power-plug insertion hole  110   a  through the power-saving circuit. When the signal input unit  200  is disconnected, an operation signal applied to a switch unit in the power-saving circuit is cut off such that the plug socket is switched to a normal power-off mode. Thus, when the signal input unit  200  is disconnected, the power supply to the outside or the connected electrical device is cut off. 
         [0071]      FIGS. 5A ,  5 B, and  5 C are a front view, a side view, and a rear view of the plug socket of  FIG. 3 . Specifically,  FIG. 5A  is a front view of the socket assembly,  FIG. 5B  is a side view showing the socket assembly connected to the main body portion, and  FIG. 5C  is a rear view of the socket assembly and the main body portion. Referring to  FIG. 5A , the plug socket  100   b  includes the power plug mounting portion  112   b,  the jack mounting portion  142   b,  and the mode setting unit  130 , which are provided on the front surface of the socket assembly, as shown in  FIG. 4 . The power plug mounting portion  112   b  includes an electrode insertion portion  113   b  in which an electrode of the plug is inserted and a ground portion  114   b  providing a ground to the plug. 
         [0072]    Moreover, the socket assembly  102   b  includes at least one screw hole through which a screw is inserted to fix the socket assembly  102  to a wall and at least one fixing portion into which the front surface portion is inserted and fixed. 
         [0073]    Referring to  FIG. 5B , the main body portion  103   b  is connected to the rear surface of the socket assembly  102   b.  In this case, the power plug mounting portion  112   b,  the jack mounting portion  142   b,  and the mode setting unit  130  of the socket assembly  102   b  are connected to the circuit board inside the main body portion  103   b.    
         [0074]    Referring to  FIG. 5C , the plug socket  100   b  includes a rear surface housing  118  connected to the rear surface of the socket assembly  102   b,  and the rear surface housing  118  has a rectangular cover structure to protect the circuit board inside the main body portion  103   b  and the power-saving circuit mounted on the circuit board such that the power-saving circuit is not exposed to the outside. 
         [0075]    The rear surface housing  118  includes a first power connection portion  115  for applying external power to the power-saving circuit, a second power connection portion  116  supplying electric power of the power-saving circuit to the outside, and a power-line disconnecting and fixing portion  117  capable of fixing or disconnecting an inserted power line. 
         [0076]    The power-line disconnecting and fixing portion  117  closes the first and second power connection portions  115  and  116  in a normal state to fix the power line inserted into the power connection portions  115  and  116  and prevents foreign materials from entering the power connection portions  115  and  116  when the power line is not connected. 
         [0077]    Moreover, the power-line disconnecting and fixing portion  117  opens the power connection portions  115  and  116 , when two power-line disconnecting and fixing portions  117  are operated to face each other, to allow the user to insert the power line to the power connection portions  115  and  116  or remove the inserted power line therefrom. 
         [0078]      FIG. 6  is a diagram showing the mode setting unit of the plug socket of  FIGS. 1 and 3 . 
         [0079]    As shown in  FIG. 6 , the mode setting unit  13 ,  130  in the plug socket includes a predetermined input means capable of setting a mode in multi-steps such that electric power to an electrical device or any other plug socket connected to the plug socket is supplied or cut off. 
         [0080]    Here, the mode setting unit  13 ,  130  may be a slide switch capable of setting the mode in three steps; however, a rotary switch, a plurality of buttons, or a DIP switch capable of setting the mode in at least three steps may be used. 
         [0081]    The mode setting unit  13 ,  130  sets the mode according to the position of a switch bar  132  and applies mode information to the power-saving circuit. Here, the mode setting unit  13 ,  130  may set three modes such as an optional automatic mode, an automatic mode, and a manual/timer mode. 
         [0082]    When the switch bar  132  is located at a first position  135 , the mode setting unit  13 ,  130  applies a signal for setting the optional automatic mode to the power-saving circuit, and thus the plug socket is set to the optional automatic mode. When the switch bar  132  is located at a second position  134 , the mode setting unit  13 ,  130  applies a signal for setting the automatic mode to the power-saving circuit, and thus the plug socket is set to the automatic mode. When the switch bar  132  is located at a third position  133 , the mode setting unit  13 ,  130  applies a signal for setting the manual/timer mode to the power-saving circuit. 
         [0083]    When any one of the modes is set by the mode setting unit  13 ,  130 , a standby time until the power is cut off, a type of a signal input from the signal input unit  200 , a method of inputting the signal, and a type of an input control command are set differently according to the set mode of the plug socket. 
         [0084]    As mentioned above, the plug socket includes the signal input unit  200  detachably connected to the socket main body  10 ,  100   a,    100   b  by a lead wire to input a predetermined control signal relating to the power supply or power cut-off to an electrical device or any other plug socket connected to the plug socket. 
         [0085]    The signal input unit  200  includes the first signal input unit  40  receiving a radio signal and a control signal by a manual operation and inputting an operation signal, and the second signal input unit  50  inputting an operation signal by a manual operation or a control signal by a timer. 
         [0086]      FIG. 7  is a perspective view showing the first signal input unit connected to the plug socket of  FIGS. 1 and 3 . 
         [0087]    Referring to  FIG. 7 , the first signal input unit  40  includes a connection plug  43  inserted into the jack connection unit  14 ,  140 ,  420 , a main body  45  including a signal receiving unit  41  and an input unit  42 , and a lead wire  46  connecting the main body  45  to the connection plug  43 . 
         [0088]    The connection plug  43  includes a connection portion  44  in the form of an earplug detachably connected to the jack connection unit  14 ,  140 ,  420 . The connection portion  44  consists of a plurality of connection terminals  44  such that, when the connection plug  43  is inserted into the jack connection unit  14 ,  140 ,  420 , each connection terminal  44  is connected to a signal terminal provided in the jack connection unit  14 ,  140 ,  420  to deliver a signal. 
         [0089]    The input unit  42  includes at least a button for applying an operation signal when it is pressed. 
         [0090]    The signal receiving unit  41  includes a radio signal module for receiving an infrared signal or any other radio signal and receives a signal output from a remote controller of the electrical device, such as a television (TV) set, a radio, an air conditioner, a video player, etc., or any other radio signal. 
         [0091]    When a radio signal is received via the signal receiving unit  41 , the first signal input unit  40  applies the received radio signal to the plug socket through the connection plug  43 . When the button of the input unit  42  is pressed, the first signal input unit  40  applies a predetermined operation signal to the power-saving circuit of the plug socket through the connection plug  43 . 
         [0092]      FIG. 8  is a perspective view showing the second signal input unit  50  connected to the plug socket of  FIGS. 1 and 3 . 
         [0093]    Referring to  FIG. 8 , the second signal input unit  50  includes a connection plug  56  inserted into the jack connection unit  14 ,  140 ,  420 , a time input unit  51 , a time output unit  52 , a first housing  53  formed of a transparent or translucent material covering the time output unit  52 , a main body  55  that is a housing for accommodating the time input unit  51 , the time output unit  52 , and a control circuit provided therein, and a lead wire  58  connecting the main body  55  to the connection plug  56 . 
         [0094]    The connection plug  56  has the same shape as the first signal input unit  40 , and thus includes a plurality of connection terminals  57 . The connection plug  56  is inserted into the jack connection unit  14 ,  140 ,  420  to apply a predetermined control signal to the power-saving circuit. 
         [0095]    The time input unit  51  includes at least one push button to input a set time of a timer corresponding to the number of times the button is pressed. In this case, the time input unit  51  inputs different signals when the button is pressed one time and when the button is pressed for more than a predetermined time (long key input). 
         [0096]    The time output unit  52  displays a timer time input by the time input unit  51 . The time output unit  52  displays the time increased or decreased by the operation of the time input unit  51 . The time output unit  52  may include, but is not limited to, an LCD capable of outputting, for example, a four digit number. 
         [0097]    In this case, the time output unit  52  displays the hour in the first two digits and the minutes in the last two digits. For example, 03:30 represents three hours and thirty minutes. 
         [0098]    When the timer time set by the time input unit  51  has elapsed, the second signal input unit  50  delivers an operation signal generated from the control circuit to the power-saving circuit of the plug socket through the connection plug  56 . 
         [0099]      FIG. 9  is a block diagram showing a configuration of the plug socket of  FIGS. 1 and 3 . 
         [0100]    As shown in  FIG. 9 , the plug socket includes a power input terminal  440 , a power output terminal  450 , a signal input unit  200 , a mode setting unit  380 , a jack connection unit  420 , and a power-saving circuit  470 . The plug socket further includes a changeover switch  460  capable of being manually operated. The power input terminal  440  is connected to the power input unit  12  of the first embodiment and the power connection portions  115  of the second embodiment to supply electric power to the plug socket. The power input terminal  440  is connected to the power output unit  15  of the first embodiment and the power-plug insertion hole  110   a,    110   b  and the power connection portions  116  of the second embodiment such that the electric power of the power input terminal  440  is supplied to the connected electrical device or any other plug socket through the power-saving circuit  470 . 
         [0101]    When any one of the optional automatic mode, the automatic mode, and the manual/timer mode is selected, the mode setting unit  380  transmits information regarding the selected mode to the power-saving circuit  470 . 
         [0102]    The signal input unit  200  is detachably connected to the jack connection unit  420  and inputs a predetermined control signal relating to the power supply or power cut-off. The signal input unit  200  is connected to the jack connection unit  420  by a lead wire and includes the first signal input unit  40  having the radio signal module for receiving an infrared or any other radio signal and a button applying a signal when it is pressed, and the second signal input unit  50  capable of setting a timer. 
         [0103]    In this case, when the signal input unit  200  is connected to the jack connection unit  420 , the plug socket operates in a power-saving mode to cut off standby power for the electrical device or any other plug socket by the power-saving circuit. 
         [0104]    On the other hand, when the signal input unit  200  is disconnected from the jack connection unit  420 , the plug socket is switched to a normal power-off mode, thus safely cutting off the power supply to the outside or the connected electrical device. 
         [0105]    When the signal input unit  200  is disconnected from the jack connection unit  420 , the connection between a switch unit  330  and a drive circuit  320  or a control unit  310  is cut off such that the switch unit  330  is turned off. Thus, the plug socket is switched to an automatic power-off mode and the power supply to the connected electrical device or any other plug socket is cut off. Moreover, when the signal input unit  200  is disconnected from the jack connection unit  420 , the power supplied to the control unit  310  is cut off, and thus the control unit  310  cannot perform the control operation according to the power supply or power cut-off. 
         [0106]    When the power supply is cut off as the signal input unit  200  is disconnected from the jack connection unit  420 , the changeover switch  460  may be operated by the user to enable the power supply such that the plug socket is switched to a normal power-on mode in the event of failure of the power-saving circuit. 
         [0107]    In this case, when the changeover switch  460  is operated by the user, the switch unit  330  included in the power-saving circuit is forcibly turned on without a control signal of the control unit  310  such that the power is supplied to the connected electrical device or any other plug socket. At this time, since the power is supplied regardless of the control of the control unit  310  when the power supply is made by the operation of the changeover switch  460 , the plug socket operates in the normal power-on mode. 
         [0108]    Since the power supply is cut off when the signal input unit  200  is disconnected from the jack connection unit  420 , the changeover switch  460  can be used to switch the plug socket into the normal power-on mode in the event that the use of the plug socket is impossible due to a failure of the power-saving circuit or when there is no signal input unit  200 . 
         [0109]    The power-saving circuit  470  detects a load current with respect to the electric power flowing from the power input terminal  440  to the power output terminal  450  to determine an operation state of the connected electrical device or any other plug socket, thus supplying or cutting off the electric power to the connected electrical device or any other plug socket. 
         [0110]    The power-saving circuit  470  includes the switch unit  330 , a power supply unit  350 , the drive circuit  320 , a load current detection unit  410 , a state output unit  360 , a learning unit  370 , a data unit  390 , and the control unit  310  controlling the entire operation of the power-saving circuit  470  and the plug socket. 
         [0111]    The power-saving circuit  470  further includes a backup data unit  400 . 
         [0112]    The switch unit  330  is connected between the power input terminal  440  and the power output terminal  450  to allow the electric power to the electrical device or any other plug socket to be supplied or cut off. In this case, the switch unit  330  may be a relay turned on/off by the electric power supplied by the drive circuit  320 . Alternatively, the switch unit  330  may be any switchable element such as a transistor. 
         [0113]    The drive circuit  320  applies electric power to the switch unit  330  in response to the control command from the control unit  310  to control the switching operation of the switch unit  330 . The drive circuit  320  includes a plurality of diodes, transistors, resistors, and capacitors. 
         [0114]    The power supply unit  350  converts the electric power input from the power input terminal  440  and supplies a driving power to the control unit  310 . The power supply unit  350  converts an AC voltage applied from the power input terminal  440  into a DC voltage and stabilizes the converted DC voltage. At this time, the power supply unit  350  applies the DC voltage to the control unit  310  or the drive circuit  320  such that the power-saving circuit is operated. 
         [0115]    The data unit  390  stores a load detection value, which is a reference value to determine that the power supply is automatically cut off as the control unit  310  controls the switch unit  330  to be switched according to a load signal input from the load current detection unit  410 , and stores a delay time until the power supply is cut off, data for recognizing the operation signal input from the signal input unit  200 , and data learned by the learning unit  370 . The backup data unit  400  stores the data stored in the data unit  390  such as the load detection value, the delay time data, the operation signal recognizing data, and the learned data. 
         [0116]    When the mode setting unit  380  sets the optional automatic mode, the learning unit  370  sets a new reference value of the power cut-off according to the load current detected by the load current detection unit  410 . The newly set reference value is stored as the learned data in the data unit  390  and used as a reference value of the control unit  310  when the optional automatic mode is maintained. Moreover, the learning unit  370  registers an infrared or any other radio signal input from the first signal input unit  40  and stores it in the data unit  390 . 
         [0117]    The state output unit  360  is turned on and off according to the power supply state by the power-saving circuit, i.e., according to whether the electric power is normally supplied or cut off and outputs state information. In this case, a lamp turned on and off may be used as the state output unit  360 . 
         [0118]    The load current detection unit  410  detects a load current from the electric power supplied by the switch unit  330  and inputs a load signal to the control unit  310 . 
         [0119]    When the electric power is supplied to the electrical device or any other plug socket as the switch unit  330  is turned on, the load current detection unit  410  detects a load current from the supplied electric power, removes power noise or overvoltage contained in the electric power, converts it into a DC voltage, and outputs a load signal to the control unit  310  to determine the operation state of the electrical device or any other plug socket. 
         [0120]    The control unit  310  controls the drive circuit  320  to allow the switch unit  330  to operate in response to the operation signal, the infrared signal or any other radio signal input from the signal input unit  200  or the load signal input from the load current detection unit  410 . 
         [0121]    When the operation signal is input from the signal input unit  200 , the control unit  310  generates a control command and applies it to the drive circuit  320  such that the switch unit  330  is turned on and thus the electric power is supplied to the electrical device or any other plug socket. At this time, the control unit  310  receives the operation signal from the signal input unit  200  and determines whether to supply or cut off the electric power in response to the mode set by the mode setting unit  380 . 
         [0122]    Moreover, the control unit  310  detects the mounting state of the signal input unit  200  from the jack connection unit  420  and supplies or cuts off the electric power according to the mounting state. When it is detected that the signal input unit  200  is connected to the jack connection unit  420 , the control unit  310  switches the plug socket to the power supply state immediately. 
         [0123]    When the signal input unit  200  is connected to the jack connection unit  420 , the control unit  310  determines the operation state of the electrical device or a plurality of electrical devices connected to another plug socket based on the load signal input from the load current detection unit  410  and applies a control command to the drive circuit  320  such that the electric power is automatically supplied or cut off. 
         [0124]    The control unit  310  compares the load signal input from the load current detection unit  410  with a predetermined load detection value and, if the load signal is less than the load detection value, determines a standby power state as the electric power of the electrical device or the plurality of electrical devices connected to another plug socket is cut off. Thus, the control unit  310  controls the electric power to be automatically cut off after a predetermined time elapses. 
         [0125]    When the automatic mode is set by the mode setting unit  380 , the control unit  310  receives a load signal corresponding to the load current measured by the load current detection unit  410  and compares the received load signal with a predetermined reference value, thus determining the operation state of the electrical device or any other plug socket connected to the power output terminal  450 . If the load signal is less than the reference value, the control unit  310  determines that the operation of the electrical device or any other plug socket is stopped, i.e., determines that standby power is consumed, and controls the switch unit  330  to be turned off such that the electric power supplied to the electrical device or any other plug socket is automatically cut off. 
         [0126]    When the operation signal is input from the signal input unit  200  during the automatic mode, the control unit  310  controls the switch unit  330  to release the power cut-off such that the electric power is supplied to the electrical device or any other plug socket. In the case where the signal input unit  200  is the first signal input unit  40 , when an infrared signal or any other radio signal is input, a signal is applied from the first signal input unit  40  to the control unit  310  and, when the button of the input unit is operated, an operation signal is applied to the control unit  310 . Moreover, in the case where the signal input unit  200  is the second signal input unit  50 , when the time input unit  51  is operated, an operation signal is applied to the control unit  310 . 
         [0127]    In this case, the control unit  310  controls the learning unit  370  at the initial stage of the automatic mode such that the infrared signal or any other radio signal of the first signal input unit  40  is registered. The learning unit  370  registers the input infrared signal or any other radio signal in response to the signal input from the input unit  42  of the first signal input unit  40  based on the control command of the control unit  310  and stores the infrared signal or any other radio signal in the data unit  390 . 
         [0128]    For example, when the button of the input unit  42  of the first signal input unit  40  is pressed for more than a predetermined time, the control unit  310  controls the learning unit  370  to register the infrared signal or any other radio signal. Moreover, when the signal can be registered in the above manner, the signal receiving unit  41  of the first signal input unit  40  receives a signal output when the remote controller is operated by the user and applies the received signal to the plug socket, and the learning unit  370  registers the input infrared signal or any other radio signal. 
         [0129]    Here, when the infrared signal or any other radio signal can be registered, the control unit  310  controls the state output unit  360  to allow the user to recognize that the registration of the infrared signal or any other radio signal is available. When the registration of the infrared signal or any other radio signal is completed by the learning unit  370 , the control unit  310  controls the state output unit  360  to display the result. When a lamp is provided in the first signal input unit  40 , the control unit  310  applies a predetermined signal to the first signal input unit  40  to inform that the signal registration is available or completed through the lamp provided in the first signal input unit  40 . 
         [0130]    As such, when the infrared signal or any other radio signal is registered by the learning unit  370 , the control unit  310  compares an infrared signal or any other radio signal input from the first signal input unit  40  with the registered signal. When they are the same signal, the control unit  310  recognizes the input signal as an operation signal and thus controls the switch unit  330  to release the power cut-off such that the electric power is supplied to the electrical device or any other plug socket. When the input signal is different from the registered signal, the control unit  310  ignores the input signal. 
         [0131]    When the manual/timer mode is set by the mode setting unit  380 , the control unit  310  supplies or cuts off the electric power to the connected electrical device or any other plug socket according to the operation signal input from the signal input unit  200 . 
         [0132]    At this time, when the operation signal is input from the signal input unit  200  while the electric power is supplied to the electrical device or any other plug socket, the control unit  310  controls the switch unit  330  to supply or cut off the electric power regardless of the load signal of the load current detection unit  410 . 
         [0133]    Moreover, when the optional automatic mode is set, the control unit  310  controls the learning unit  370  to perform a standby power learning mode. At this time, the control unit  310  determines the operation state of the electrical device or any other plug socket based on the load signal of the load current detection unit  410  using a reference value newly set by the learning unit  370  and controls the switch unit  330 . 
         [0134]    At this time, the learning unit  370  receives a load current value measured by the load current detection unit  410  according to the control command of the control unit  310 , sets a standby power value corresponding to the received value as a new reference value, and stores the set value in the data unit  390 . 
         [0135]    That is, the learning unit  370  controls the load current detection unit  410  to measure the standby power consumed by the connected electrical device or any other plug socket for a predetermined time. The learning unit  370  automatically sets the load detection value for the power cut-off and the delay time until the power is cut off in response to the magnitude of the standby power measured by the load current detection unit  410 . 
         [0136]    At this time, the control unit  310  controls the lamp of the state output unit  360  to be turned on and off, thus displaying the learning mode state. 
         [0137]    Here, the load current detection unit  410  includes a conversion unit (not shown) connected to the switch unit  330  and the power output terminal  450  to detect a load current from the supplied power, remove overvoltage or overcurrent contained in the detected AC voltage, and convert the AC voltage into a ripple voltage, a smoothing unit (not shown) smoothing the ripple voltage and applying a DC load signal to the control unit  310 , and a discharge unit (not shown). However, detailed descriptions thereof will be omitted for brevity. 
         [0138]    Moreover, when the optional automatic mode is set, the control unit  310  controls the learning unit  370  in the same manner as the above-described automatic mode such that the infrared signal or any other radio signal is registered and, once the registration of the infrared signal or any other radio signal is completed, cuts off the power supply in response to the registered signal. 
         [0139]    Here, when the registration of the infrared signal or any other radio signal is completed during the automatic mode, the registered signal can be used when the automatic mode is switched to the optional automatic mode without signal registration. The infrared signal or any other radio signal registered in the optional automatic mode can also be used in the automatic mode. At this time, the registered infrared or radio signal is stored in the data unit  390 . 
         [0140]    The plug socket may further include a noise removing unit (not shown). 
         [0141]    The noise removing unit absorbs and removes noise input from the power output terminal  450 . In this case, the noise removing unit may be connected between the switch unit  330  of the power-saving circuit and the power output terminal  450  and include a diode connected across the power output terminal  450 . 
         [0142]      FIG. 10  is a block diagram showing a configuration of the first signal input unit of  FIG. 7 . 
         [0143]    Referring to  FIGS. 7 and 10 , the first signal input unit  40  includes the connection plug  43 , the signal receiving unit  41 , and the input unit  42 . The first signal input unit  40  further includes a signal output unit  49  outputting signals of the signal receiving unit  41  and the input unit  42  to the socket main body  10 ,  100   a,    100   b . The first signal input unit  40  may further include a lamp for indicating an operation state. 
         [0144]    The first signal input unit  40  may perform a remote controller setting operation such that an infrared signal or any other radio signal of a specific remote controller is registered and stored by the control unit  310  and the learning unit  370 . In this case, the registration of the infrared signal or any other radio signal may be performed when the plug socket is in the automatic mode or the optional automatic mode. 
         [0145]    When the registration of the infrared signal or any other radio signal is completed by the first signal input unit  40 , the control unit  310  recognizes the input signal as the operation signal only when the infrared signal or any other radio signal input from the first signal input unit  40  is the registered signal and ignores a signal from any other remote controller. Here, a plurality of infrared signals or other radio signals may be registered, and an infrared signal or any other radio signal for each button in one remote controller may be registered. 
         [0146]    Here, when the button of the input unit  42  is pressed for more than a predetermined time, the first signal input unit  40  applies a corresponding signal to the control unit  310 , which switches to an infrared signal or any other radio signal setting mode to receive an infrared signal or any other radio signal through the signal receiving unit  41  and control the learning unit  370  to register the received infrared signal or any other radio signal. 
         [0147]    In the case where the plug socket is in the automatic mode or the optional automatic mode, when an infrared signal or any other radio signal is received from the signal receiving unit  41  while the connection plug  43  is mounted on the socket main body  10 ,  100   a,    100   b,  the first signal input unit  40  applies the infrared signal or any other radio signal to the signal output unit  49  and delivers a signal to the jack connection unit  420  of the plug socket through the connection plug  43 . 
         [0148]    The control unit  310  which has received the infrared signal or any other radio signal from the jack connection unit  420  compares the received signal with the registered infrared or radio signal and, if the received signal is the registered signal, controls the drive circuit  320  by generating an operation signal to release the power cut-off and supply a electric power. Thus, the switch unit  330  is turned on and the electric power is supplied to the electrical device or any other plug socket. 
         [0149]    Moreover, the first signal input unit  40  applies an operation signal for the power supply to the plug socket in response to the operation of the button of the input unit  42 . 
         [0150]    A remote controller of the connected electrical device may be used as the first signal input unit  40  without a dedicated remote controller, and a specific remote controller may be designated and used since it can be set to receive only an infrared signal or any other radio signal of a specific frequency set by learning. 
         [0151]    Meanwhile, in the case where the plug socket is set to the manual/timer mode, when the button of the input unit  42  of the first signal input unit  40  is pressed, an operation signal is applied from the signal output unit  49  to the plug socket through the connection plug  43 . Then, the control unit  310  controls the electric power to be supplied or cut off in response to the operation signal input from the manual/timer mode. 
         [0152]    For example, in the case where the plug socket is set to the manual/timer mode, when the input unit  42  of the first signal input unit  40  is operated once, the control unit  310  receives an operation signal through the jack connection unit  420  to cut off the supplied power or supply the cut-off power. The electric power is cut off or supplied each time the operation signal of the first signal input unit  40  is input, which may be used when the electric power is manually cut off or supplied by the user. 
         [0153]    However, when the plug socket is set to the manual/timer mode, since the first signal input unit  40  does not have the timer function, the plug socket performs only the power supply or power cut-off according to the manual operation. 
         [0154]      FIG. 11  is a block diagram showing a configuration of the second signal input unit of  FIG. 8 . 
         [0155]    Referring to  FIGS. 8 and 11 , the second signal input unit  50  includes the connection plug  56 , the time input unit  51 , and the time output unit  52 . Moreover, the second signal input unit  50  includes a timer control unit  61  controlling input and output of a signal and controlling the entire operation of the second signal input unit  50 , a timer data unit  62  in which time set data is stored, and a timer signal output unit  63  transmitting a timer control signal generated by the timer control unit  61  to the socket main body  10 ,  100   a,    100   b  through the connection plug  56 . 
         [0156]    In this case, the time input unit  51  increases the set time of the timer corresponding to the number of times the button is pressed and inputs the increased timer time. The set time of the timer is increased within a given maximum time and, when reaching the maximum time, it is decreased corresponding to the number of times the button is pressed or increased from zero. 
         [0157]    Moreover, when the button of the time input unit  51  is pressed for more than a predetermined time (long key input), the time input unit  51  initializes the input set time and, at the same time, stops the operation of the second signal input unit  50 . Furthermore, when the button of the time input unit  51  is continuously pressed a predetermined number of times, the set time is repeated such that the operation signal may be transmitted periodically. 
         [0158]    In this case, the second signal input unit  50  may further include a setting switch unit (not shown) for allowing the set time to be repeated periodically. 
         [0159]    The time input unit  51  divides the given maximum time into a plurality of time frames such that the time is increased in different increments at each time frame. 
         [0160]    For example, the time input unit  51  inputs the set time of the timer increased in increments of 10 minutes each time the button of the time input unit  51  is pressed in a first time frame, increments of 20 minutes in a second time frame, increments of 30 minutes in a third time frame, and increments of 1 hour in a fourth time frame. 
         [0161]    That is, if the given maximum time is about 20 hours, the set time of the timer may be increased in increments of 10 minutes each time the button of the time input unit  51  is pressed up to 40 minutes, increments of 20 minutes up to 2 hours, increments of 30 minutes up to 4 hours, and increments of 1 hour up to 20 hours, the maximum time. 
         [0162]    When the set time of the timer is input by the time input unit  51 , the timer control unit  61  counts the time and, when the time reaches the set time, outputs a control signal according to the power cut-off or power supply to the plug socket. 
         [0163]    The second signal input unit  50  having the above-described configuration, which is mounted in the socket main body  10 ,  100   a,    100   b,  applies an operation signal to the control unit  310  in response to the timer time set by the operation of the time input unit  51  such that the electric power is supplied or cut off. Moreover, when the timer time is set to be repeated, the second signal input unit  50  counts the set time of the timer periodically and applies an operation signal to the control unit  310 . 
         [0164]    When the plug socket is in the manual/timer mode, the second signal input unit  50  applies an operation signal according to the timer time set in the above manner and, when the plug socket is in the automatic mode or optional automatic mode, applies an operation signal during operation of the time input unit  51  to supply the cut-off electric power. That is, when the plug socket is in the automatic mode or optional automatic mode, the time input unit  51  of the second signal input unit  50  operates in the same manner as the input unit  42  of the first signal input unit  40 . 
         [0165]      FIGS. 12A and 12B  are diagrams showing examples of use of the plug socket of  FIGS. 1 and 3 . 
         [0166]    As shown in  FIGS. 12A and 12B , the plug socket is connected to an electrical device or any other plug socket to supply or cut off electric power to the connected electrical device or any other plug socket. 
         [0167]    In the case where the signal input unit  200  is connected to one side of the connected electrical device, when the power of the electrical device is turned off, the power supply is automatically cut off to prevent standby power consumption and, when the user operates the signal input unit  200  using a remote controller or directly presses the button provided on the signal input unit  200 , an operation signal is input from the signal input unit  200  to allow the electric power to be supplied to the electrical device. 
         [0168]    Accordingly, the electric power is normally supplied to the electrical device and, when the user drives the electrical device, the electrical device normally operates. Then, when a load current is detected by the load current detection unit  410  as the power is consumed, the control unit  310  continuously switches the switch unit  330  through the drive circuit  320  while not being affected by the infrared signal or any other radio signal or the operation of the button. 
         [0169]    For example, in the case where the first signal input unit  40  is connected to any part of the front surface of the TV set, when the power of the TV set is turned off during the automatic mode of the plug socket, the power supplied to the TV set is automatically cut off by the power-saving circuit after a predetermined time elapses. Then, when a remote controller is operated by the user, the first signal input unit  40  receives an infrared signal or any other radio signal and applies an operation signal to the power-saving circuit such that the electric power is supplied to the electrical device. Next, when the remote controller is operated once again, the TV set receives a signal from the remote controller and is driven. 
         [0170]    Here, since the power of the TV set is cut off during the first operation of the remote controller, the TV set cannot receive the remote control signal; however, since the electric power is normally supplied to the TV set during the second operation of the remote controller, the TV set can receive the remote control signal using the standby power. 
         [0171]    Moreover, in the case where an electric mat is connected to the plug socket in the manual/timer mode and the first signal input unit is connected to the electric mat, when the button of the first signal input unit is pressed or a remote controller is operated, the power supply to the electric mat is cut off, and thus the operation of the electric mat is stopped. Then, when the button is pressed one time or the remote controller is operated, the electric power is supplied to the electric mat, and thus the operation of the electric mat is restarted. 
         [0172]    When the second signal input unit is connected to the electric mat and the timer is set, the electric mat is operated until the set time. After the set time elapses, the power supply to the electric mat is cut off and the operation of the electric mat is stopped. At this time, when the second signal input unit is set to the repetitive mode, the electric power is supplied after the set time elapses, and thus the operation of the electric mat is restarted. 
         [0173]    Operation of the plug socket having the above configuration in accordance with the present invention will now be described. 
         [0174]      FIG. 13  is a flowchart showing a mode setting method of the plug socket of  FIGS. 1 and 3 . 
         [0175]    As shown in  FIG. 13 , the plug socket is operated in a power-saving mode or normal power-off mode according to whether the signal input unit  200  is connected to the jack connection unit  420 . 
         [0176]    When the signal input unit  200  is not connected to the jack connection unit  420  (S 520 ), the connection between the control unit  310  or the drive circuit  320  and the switch unit  330  is cut off, and thus the switch unit  330  is turned off and the power supply to the connected electrical device or any other plug socket is cut off. Thus, the plug socket is operated in the normal power-off mode (S 610 ). At this time, the operation power applied to the control unit  310  is also cut off, and thus the control unit  310  is not operated. 
         [0177]    When the signal input unit  200  is connected to the jack connection unit  420 , the operation power is supplied to the control unit  310  and the connection with the switch unit  330  is restored. Thus, the drive circuit  320  controls the switch unit  330  under the control of the control unit  310 , and thus the switch unit  330  can perform the switching operation. 
         [0178]    When the signal input unit  200  is connected to the jack connection unit  420  (S 520 ), the plug socket is operated in the power-saving mode such that the electric power input from the power input terminal  440  is supplied to the power output terminal  450  through the power-saving circuit. Thus, the electric power is supplied to the connected electrical device or any other plug socket, and then the control unit  310  determines the operation state of the electrical device or any other plug socket based on the load current and supplies or cuts off the electric power based on the determination result (S 530 ). 
         [0179]    When the set mode of the mode setting unit  380  is the automatic mode (S 540 ), the control unit  310  sets the automatic mode (S 550 ) in which the control unit  310  compares a load signal applied from the load current detection unit  410  with the reference value to control the switch unit  330  such that the electric power supplied to the electrical device or any other plug socket is controlled, and controls the electric power to be supplied to the electrical device or any other plug socket in response to the infrared signal or any other radio signal input from the signal input unit  200  or an operation signal according to the operation of the button. 
         [0180]    At this time, the control unit  310  may control the learning unit  370  to register an infrared signal or any other radio signal of a specific remote controller among the infrared signals or other radio signals input from the signal input unit  200  (S 560 ). When the registered infrared or radio signal is input, the control unit  310  recognizes the input signal as an operation signal and controls the switching operation of the switch unit  330 . Moreover, the control unit  310  receives an operation signal according to the operation of the input unit  41  of the signal input unit  200  and controls the switch unit  330 . 
         [0181]    When the set mode of the mode setting unit  380  is the optional automatic mode, the control unit  310  sets the optional automatic mode (S 580 ) in which the control unit  310  resets a reference value by measuring the standby power and learning a value of a specific remote controller in the same manner as the automatic mode and compares the reset reference value with the load signal to control the power supply. 
         [0182]    In the optional automatic mode, the control unit  310  controls the learning unit  370  to register an infrared signal or any other radio signal of a specific remote controller in the same manner as the automatic mode, detects a load current through the load current detection unit  410 , calculates a standby power value based on the detection value, and sets a new reference value (S 590 ). 
         [0183]    The registered infrared or radio signal may be used in the other modes regardless of the set modes. 
         [0184]    Meanwhile, when the set mode of the mode setting unit  380  is the manual/timer mode, the control unit  310  sets the manual/timer mode (S 600 ), in which the control unit  310  controls the switch unit  330  to supply or cut off the electric power to the electrical device or any other plug socket in response to an operation signal of the signal input unit  200 . 
         [0185]    Operation of the plug socket in each mode set by the mode setting unit  380  will now be described. 
         [0186]      FIG. 14  is a flowchart showing an operation in the automatic mode of the plug socket of  FIGS. 1 and 3 . 
         [0187]    Referring to  FIG. 14 , when the plug socket is set to the automatic mode (S 620 ), the electric power input from the power input terminal  440  is applied to the power output terminal  450  through the power-saving circuit  470  and then supplied to the connected electrical device or any other plug socket. 
         [0188]    At this time, the load current detection unit  410  measures a load current from the electric power flowing through the power-saving circuit  470  and applies a load signal according to the load current to the control unit  310 . The control unit  310  compares the input load signal with a predetermined reference value to determine whether standby power is consumed (S 640 ). 
         [0189]    When the load signal is less than the predetermined reference value, the control unit  310  determines that the operation of the connected electrical device or any other plug socket is stopped and standby power is consumed and stands by for a predetermined delay time (S 650 ). After the predetermined delay time elapses, the control unit  310  controls the switch unit  330  to be turned off to cut off the power supply to the connected electrical device (S 660 ). At this time, the drive circuit  320  controls the operation of the switch unit  330  to be turned off in response to the control command of the control unit  310 . 
         [0190]    When the switch unit  330  is turned off in the above manner, the electric power applied from the power input terminal  440  to the power output terminal  450  is cut off, and thus the electric power is not supplied to the connected electrical device. 
         [0191]    When an operation signal according to the operation of the button is input from the signal input unit  200  (S 670 ), the control unit  310  controls the switch unit  330  to be turned on to supply the electric power to the connected electrical device (S 680 ). 
         [0192]    Moreover, when an infrared signal or any other radio signal is input from the signal input unit  200 , the control unit  310  compares the input infrared or radio signal with a registered signal. When they are the same signal, the control unit  310  recognizes the input signal as an operation signal and controls the switch unit  330  to be turned on to supply the electric power to the connected electrical device. Meanwhile, when the input signal is different from the registered signal, the control unit  310  ignores the input signal. 
         [0193]      FIG. 15  is a flowchart showing an operation in the optional automatic mode of the plug socket of  FIGS. 1 and 3 . 
         [0194]    As shown in  FIG. 15 , when the plug socket is set to the optional automatic mode (S 690 ), the control unit  310  controls the learning unit  370  to measure and learn the infrared signal or any other radio signal of the remote controller and the standby power (S 700 ). At this time, the learning unit  370  controls the load current detection unit  410  to measure the load current for a predetermined time, sets the current standby power value as a new reference value, calculates a delay time based on the standby power value, and stores the delay time in the data unit  390  (S 710 ). At this time, the connected electrical device should be in stop and standby modes while the learning unit  370  learns the standby power. This optional automatic mode can be used when the electric power is not automatically cut off since the amount of standby power of the electrical device is greater than the reference value set in the automatic mode or when the electric power is cut off during normal operation since the amount of power consumed during operation of the electrical device is smaller than the reference value of the automatic mode. 
         [0195]    When the learning process with respect to the remote controller and the amount of standby power is completed in the above manner, the plug socket is operated in the automatic mode described with reference to  FIG. 14 . However, the control unit  310  determines whether the electric power is cut off based on a new reference value according to the learned amount of standby power and a new delay time. Moreover, in the same manner as the above-described automatic mode, the infrared signal or any other radio signal of the remote controller can be registered and used, and the registered infrared or radio signal can be used regardless of the mode. 
         [0196]    When the electric power is supplied to the electrical device through the plug socket (S 730 ), the load current detection unit  410  measures a load current (S 740 ) and inputs a load signal according to the load current to the control unit  310 . Then, the control unit  310  compares the input load signal with a reference value newly set by the learning process and determines the operation state of the electrical device. 
         [0197]    When the load signal is less than the newly set reference value (S 750 ), the control unit  310  controls the switch unit  330  to be turned off to cut off the power supply to the electrical device (S 760 ). 
         [0198]    When an operation signal is input from the signal input unit  200  while the power supply is cut off, the control unit  310  controls the switch unit  330  to supply the electric power to the electrical device. 
         [0199]      FIG. 16  is a flowchart showing an operation in the manual/timer mode of the plug socket of  FIGS. 1 and 3 . 
         [0200]    Referring to  FIG. 16 , when the plug socket is set to the manual/timer mode (S 780 ), the control unit  310  supplies or cuts off the electric power in response to an operation signal input from the signal input unit  200  connected to the jack connection unit  420 . 
         [0201]    At this time, when the operation signal is input from the signal input unit  200  while the electric power is supplied to the electrical device( 5790 ), the control unit  310  controls the switch unit  330  to be turned off to cut off the power supply to the electrical device (S 810 ). In this case, the control unit  310  cuts off the power supply immediately or after a predetermined delay time. 
         [0202]    When an operation signal is input from the signal input unit  200  (S 820 ) while the power supply to the electrical device is cut off, the control unit  310  controls the switch unit  330  to be turned on to supply the electric power to the electrical device (S 840 ) 
         [0203]    Here, in the case where the signal input unit  200  is the first signal input unit  40 , when an operation signal according to the operation of the button of the input unit  42  is input or when the registered infrared or radio signal is input, the control unit  310  recognizes the input signal as an operation signal and controls the switch unit  330  to be switched. 
         [0204]    Moreover, when the signal input unit  200  is the second signal input unit  50 , the second signal input unit  50  counts the time according to the set time of the timer and applies an operation signal to the control unit  310  after the set time of the timer elapses, and thus the control unit  310  controls the operation of the switch unit  330 . 
         [0205]      FIG. 17  is a flowchart showing an operation of the second signal input unit connected to the plug socket of  FIGS. 1 and 3 . 
         [0206]    Referring to  FIG. 17 , when the time input unit  51  of the second signal input unit  50  is operated once, the timer control unit  61  increases the set time of the timer by a predetermined time (S 860 ) and displays the increased time of the timer on the time output unit  52  (S 870 ). 
         [0207]    The timer control unit  61  repeats the operation until the timer time setting is completed (S 850  to S 880 ). At this time, when the time input unit  51  is not operated for more than a predetermined time, the timer control unit  61  determines that the timer time setting is completed. 
         [0208]    When the timer time setting is completed (S 880 ), the timer controller  61  stores the set time of the timer in the timer data unit  62  (S 890 ) and counts the time (S 900 ). 
         [0209]    When reaching the set time of the timer (S 910 ), the timer control unit  61  inputs an operation signal to the control unit  310  (S 920 ). 
         [0210]    Meanwhile, when the button of the time input unit  51  is pressed for more than a predetermined time (long key input) (S 930 ), the time input unit  51  initializes the set time of the timer and, at the same time, stops the operation of the second signal input unit  50  (S 940 ). When the button of the time input unit  51  is pressed while the operation of the second signal input unit  50 , the second signal input unit  50  is re-operated, and the timer time setting becomes available. 
         [0211]    Here, during re-operation or during the next timer time setting, the timer control unit  61  reads the last data stored in the timer data unit  62 , sets the read data as an initial value, and displays the initial value on the time output unit  52 . 
         [0212]    Moreover, when the timer time is set to be repeated, the second signal input unit  50  counts the set time of the timer repeatedly and applies an operation signal to the control unit  310  repeatedly. Thus, the electric power to the electrical device or any other plug socket connected to the plug socket is periodically supplied or cut off. 
         [0213]      FIG. 18  is a perspective view showing a configuration of a changeover switch unit  460  provided in the plug socket of  FIGS. 1 and 3 , and  FIGS. 19A and 19B  are perspective views showing a detailed configuration of the switch unit provided in the plug socket of  FIGS. 1 and 3 . 
         [0214]    As shown in  FIGS. 18 ,  19 A, and  19 B, the changeover switch  460  is directly connected to the switch unit  330  of the power-saving circuit to forcibly operate the switch unit  330 . In this case, the changeover switch unit  460  may include a push button  461 . 
         [0215]    In the case where the switch unit  330  consists of a relay, when the button  461  of the changeover switch unit  460  is pressed down, the switching structure of the switch unit  330  is forcibly operated, and thus the power supply to the connected electrical device becomes possible. 
         [0216]    The changeover switch unit  460  is used to switch the plug socket into the normal power-on mode in the event of malfunction of the power-saving circuit or in the event that there is a problem in using the electrical device as the electric power is not controlled. 
         [0217]    When the connection plug  43 ,  56  of the signal input unit  200  is disconnected from the jack connection unit  420 , since the connection between the switch unit  330  and the control unit  310  or the drive circuit  320  is cut off, the switch unit  330  is turned off to cut off the electric power, and thus the plug socket is switched to the power-off mode. In this case, the changeover switch  460  is operated to turn on the switch unit  330  regardless of the control of the control unit  310 , thus supplying the electric power. At this time, since the connection between the control unit  310  and the switch unit  330  is cut off and the operation power is not applied to the control unit  310 , the plug socket is operated only by the forcible operation of the changeover switch  460 . 
         [0218]    That is, in the event of circuit failure in the plug socket or in the event that the signal input unit  200  is disconnected from the jack connection unit  420 , it is possible to forcibly turn on the switch unit  330  by operating the changeover switch  460 , thus switching the plug socket to the normal power-on mode. 
         [0219]    The push button  461  of the changeover switch  460  is inserted into a changeover switch insertion hole  107  formed in the socket assembly  102   a,    102   b  and directly connected to the switch unit  330  mounted in circuit board B located inside the socket main body  10 ,  100   a,    100   b.  Alternatively, the changeover switch unit  460  may include a lever. 
         [0220]    As shown in  FIG. 19B , the button  461  of the changeover switch unit  460  is connected to a first terminal  334  provided in the switch unit  330  such that, when the button  461  is pressed, the first terminal  334  is forcibly pressed by the button  461  to push a first electrode  335   a  to be in contact with a second electrode  335   b.  At this time, the control signal of the drive circuit  320  connected to a first connection terminal  336  is cut off. 
         [0221]    The first electrode  335   a  is connected to a second connection terminal  337   a , the second electrode  335   b  is connected to a third connection terminal  337   b,  the second connection terminal  337   a  is connected to the power input terminal, and the third connection terminal  337   b  is connected to the power output terminal. 
         [0222]    As a result, during operation of the changeover switch unit  460 , the electrodes of the switch unit are in contact with each other such that the electric power of the power output terminal is supplied to the electrical device through the power output terminal even in the event of failure of the power-saving circuit. 
         [0223]    As described above, according to the plug socket of the present invention, it is possible to automatically supply or cut off electric power to the electrical device or any other plug socket connect to the plug socket by detecting a load current of the electric power, thus preventing the waste of standby power and reducing unnecessary power consumption. Moreover, since the electric power is supplied only when the electrical device connected to the plug socket is used, it is possible to prevent electrical accidents, protect the electrical device, and reduce the cost. Although the plugs and the plug sockets used in different countries have different shapes, in the case of the adaptor type plug socket, the socket main body can be used in common, and thus it is unnecessary to manufacture different socket main bodies for different countries. 
         [0224]    Moreover, the plug socket according to the present invention can change the method for supplying or cutting off electric power to the electrical device according to the mode selection such that the power supply can be automatically or manually cut off. Furthermore, even in the event of circuit failure in the plug socket or in the event that the signal input unit is disconnected from the jack connection unit, it is possible to forcibly turn on the switch unit by operating the changeover switch, thus switching the plug socket to the normal power-on mode. 
         [0225]    When the technique of the present invention is used in the home network system, it is possible to prevent unnecessary power consumption due to communication standby power of about 5 to 10 W consumed even when the communication device is turned off. 
         [0226]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.