JP4871924B2 - Network equipment - Google Patents

Description

  The present invention relates to a power-saving type network device, and in particular, in an Ethernet (registered trademark) switching hub having a plurality of ports, the power-saving mode or the normal mode can be selected according to the length of the network cable. The present invention relates to a network device with a power saving mode function capable of reducing power.

  In recent years when global warming is advancing, green IT technology that considers environmental protection through power saving has become increasingly important. As an example of this type of conventional power saving technology, for example, in a HUB (concentrator) that controls a plurality of ports, a data monitoring unit that monitors data input from the ports and a power supply control unit are provided. Is known (see, for example, Patent Document 1).

  The conventional HUB described in Patent Document 1 supplies power to a communication control LSI that performs packet transfer control between ports by a power supply control unit when data is not input from all ports for a certain period of time. The HUB is suspended and the HUB is suspended. When reception data is detected at the port in the suspended state, the power supply control unit resumes power supply to the communication control LSI and restores the original state. As described above, this conventional HUB achieves power saving by performing on / off control of power supply to the HUB according to the use state of the connection node.

  As another example of the conventional power saving technology, for example, a switching hub is known that reduces power consumption by switching between a switching hub operation and a repeater hub operation by detecting a temperature abnormality inside the apparatus. (For example, refer to Patent Document 2).

  As another example of conventional power saving technology, for example, while detecting the power consumption of the entire network system, the network system is controlled so that the power consumption does not exceed a certain level, thereby realizing stable system operation. A server device and a network system are known (see, for example, Patent Document 3).

  In addition, as another example of the conventional power saving technology, for example, in a plurality of ports to which each terminal is connected, the minimum processing that does not impair the processing of communication between terminals according to the number of ports used. There has been proposed a switching hub capable of calculating a limited operation clock frequency and reducing power consumption (see, for example, Patent Document 4).

  As another example of the conventional power saving technology, for example, the operating frequency of a part of the switching hub circuit is controlled to perform the minimum necessary current supply and heat generation control, thereby reducing running cost and noise. A switching hub has been proposed (see, for example, Patent Document 5).

  The conventional switching hub described in Patent Document 5 includes a protocol processing unit, a coding unit, a decoding unit, a transmission circuit unit, a reception circuit unit, a circuit unit depending on a physical control unit, a cross bus switch unit, and a packet memory. And a common circuit unit such as a forwarding / queue control circuit unit, a frequency control circuit unit, and a VCO circuit unit. The receiving circuit unit determines the usage status of each port, and when there is an unused port, the receiving circuit unit controls the operating frequency supplied from the VCO circuit unit to be reduced by the frequency control circuit unit. . As a result, it is possible to operate with minimum necessary power without waste and to effectively use power consumption.

Further, as still another example of the conventional power saving technology, for example, a network device that reduces power consumption by determining a predetermined value of a communication data size and switching a communication speed is known (for example, a patent) Reference 6). This conventional network device determines whether or not the data size of data received from another network device is less than a predetermined value, and if it is determined that the data size is less than the predetermined value, the communication speed is increased. When the first speed is maintained and the data size is determined not to be less than the predetermined value, the communication speed is switched to the second speed higher than the first speed.
JP 2000-253035 A JP 2002-33755 A JP 2002-142385 A Japanese Patent Laid-Open No. 2002-247065 Japanese Patent No. 3606226 JP 2006-270470 A

However, the conventional power saving techniques described in Patent Documents 1 to 6 are applied to highly functional network devices, and have the following various problems (1) to (4).
(1) Communication frequency, data size, detection circuit for detecting power consumption, temperature detection, etc., an analysis unit for analyzing data detected by the detection circuit unit, and further analyzing the result of analysis by the analysis unit A control unit for controlling the frequency, the communication speed, and the supply power of the LSI is required, and the number of parts constituting the circuit for power saving increases, resulting in an increase in cost.
(2) The circuit configuration as described in the above (1) requires software control depending on a microprocessor such as a CPU and a data storage memory, and the configuration becomes complicated.
(3) In the circuit configuration as described in (1) above, it is inevitable that many circuit components themselves consume power.
(4) The power saving effect is limited because there is only one means for power saving and not intended to save power by a plurality of power saving means.

Therefore, the present invention has been made to solve the above conventional problems, and its specific purpose is as follows.
(1) Reduce circuit components for power saving,
(2) Without performing dedicated software control
(3) To provide a network device that can save power by combining and selecting a plurality of power saving means.

In order to achieve the above object, the present invention is a network device connected to a host device and a plurality of lower terminal devices via a network cable, and a plurality of power saving modes for switching between a power saving mode and a normal mode. A mode selection switch; a bias current control switching unit that controls bias currents of a plurality of LSI chips for communication control according to the selection of the power saving mode; and a transmission signal having a transmission level based on the power consumption of the power saving mode. The bias current control switching unit corresponds to each of the plurality of lower terminal devices with a predetermined length of a network cable connected to each of the plurality of lower terminal devices. Corresponding LSI chip bias current to receive the transmission signal at the transmission level based on the power consumption mode Providing a network device and controlling.

  According to the present invention, it is possible to reduce the power consumption according to the length of the network cable with a simple configuration, and it is possible to reduce costs without requiring special software processing.

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a configuration example of a power saving system using a switching hub with a power saving mode (ECO mode) function according to a typical embodiment of the present invention.

[First Embodiment]
(Configuration of power saving system)
In FIG. 1, reference numeral 1 denotes an external configuration of a switching hub with an ECO mode function, which is a typical network device according to the first embodiment. The switching hub 1 is not particularly limited, but has seven lower ports P1 to P7 and one upper port P8. These lower ports P1 to P7 are ports having power saving means for controlling so as to be able to operate in the ECO mode corresponding to the length of the network cable (cable length).

  As shown in FIG. 1, the switching hub 1 selects the ECO mode selection switch 6 in the ECO mode in order to construct a power saving system, and the two lower ports P1, P3 of the switching hub 1 and the lower terminal devices 2a, 2b is connected by network cables 4a and 4b. Examples of the lower-level terminal devices 2a and 2b include personal computers installed in the same area close to the switching hub 1 (for example, an office on the same floor as the switching hub 1). As the network cables 4a, 4b, for example, UTP (Unshielded Twist Pair) (registered trademark) cables are used. The length of the network cables 4a and 4b is not particularly limited as long as it is 100 m or less in conformity with the IEEE 802.3 standard. In the first embodiment, for example, the length is limited to a short length of 50 m. Yes.

  On the other hand, the host port P8 of the switching hub 1 and the host device (host server) 3 are connected by a network cable 5 as shown in FIG. The host device 3 includes, for example, a host gateway installed in another area far from the switching hub 1 (for example, an information management center on a floor different from the switching hub 1). As the network cable 5, the above-described UTP cable is used. The length of the cable 5 is, for example, a maximum length of 100 m in conformity with the IEEE 802.3 standard.

(Configuration of switching hub)
FIG. 2 is an operation block diagram of the switching hub in FIG. In the figure, the power saving means according to the first embodiment includes an ECO mode selection switch 6 for switching to an ECO mode and switching to a normal mode, and a PHY (Physical Layer) chip (LSI for communication control). Chip) bias current control switching units 9a and 9b for controlling bias currents of 11a and 11b. The ECO mode selection switch 6 is a dip type movable switch that sets the ECO mode or the normal mode of the switching hub 1. A configuration example for limiting the bias current of the PHY chips 11a and 11b will be described later.

  When the ECO mode selection switch 6 is selected to the ECO mode, the switching hub 1 is in the ECO mode state. In this ECO mode, the PHY chips 11a and 11b are consumed by limiting the bias currents of the PHY chips 11a and 11b to the minimum possible operation of the PHY chips 11a and 11b according to the length of the network cables 4a and 4b. In this mode, the current is adjusted. On the other hand, when the ECO mode selection switch 6 is selected to the normal mode, the switching hub 1 is in the normal mode state. In this normal mode, when it becomes necessary to connect the network cables 4a and 4b, which are limited to a short length of 50m, to a network cable having a maximum length of 100m conforming to the IEEE 802.3 standard, and to connect to the lower terminal device 2a or 2b. In addition, by setting the bias current of the PHY chips 11a and 11b to a value conforming to the IEEE 802.3 standard so that the PHY chips 11a and 11b can be surely operated according to the length of the network cable of a maximum of 100 m, the PHY chip 11a. , 11b, the current consumption is adjusted.

  When the ECO mode is selected, the bias current control switching units 9a and 9b switch from the normal mode operation to the ECO mode operation, and perform communication control for the physical layer when communicating with the lower-level terminal devices 2a and 2b. The bias current of the PHY chips 11a and 11b is limited. By limiting the bias current of the PHY chips 11a and 11b, the signal amplitude level transmitted by the PHY chips 11a and 11b is reduced. As shown in FIG. 2, the insulating pulse transformers 15a and 15b and the transmission / reception terminals 17a and 17b are connected. Via the network cables 4a and 4b whose length is limited to 50 m, they are connected to the lower-level terminal devices 2a and 2b to perform communication.

  On the other hand, even though the ECO mode selection switch 6 is selected as the ECO mode or the normal mode, the bias current control unit 10 always maintains a signal amplitude level compliant with the IEEE 802.3 standard so that the PHY chip 12 for communication control can be used. Limit the bias current. The signal amplitude level transmitted by the PHY chip 12 is set in accordance with the IEEE 802.3 standard, and the length is set to IEEE802. The host device 3 is connected via the network cable 5 that can be connected up to a maximum of 100 m defined in the three standards, and communication is performed.

(Configuration of bias current control switching unit)
Next, an example for limiting the bias current of the PHY chips 11a and 11b will be described with reference to FIG. FIG. 3 is a diagram schematically showing a configuration example of an internal circuit of the bias current control switching unit in FIG. FIG. 3 shows a state where the ECO mode selection switch 6 is selected to the ECO mode.

  In FIG. 3, the bias current control switching units 9 a and 9 b include a control signal buffer unit 90 a and a bias current switching unit 91. When the ECO mode selection switch 6 is selected to the ECO mode, the control signal in the ECO mode turns off the gate of the switching FET switch 91a for bias current control of the bias current switching unit 91 via the control signal buffer unit 90a. . By turning off the gate of the switching FET switch 91a, the bias current limiting resistor 91b and the bias current limiting resistor 91c are connected in series. The resistance value between the PHY chips 11a and 11b and the ground is the total resistance value of the bias current limiting resistor 91b and the bias current limiting resistor 91c. The current between the PHY chips 11a and 11b and the ground is adjusted by the total resistance value, and the bias current of the PHY chips 11a and 11b can be limited.

  On the other hand, when the ECO mode selection switch 6 is selected as the normal mode, the control signal in the normal mode is sent from the switching FET switch 91a of the bias current switching unit 91 via the control signal buffer unit 90a as shown in FIG. Turn on the gate. By turning on the gate of the switching FET switch 91a, the switching FET switch 91a is grounded. The resistance value between the PHY chips 11a and 11b and the ground is only the bias current limiting resistor 91b. Only the bias current control resistor 91b adjusts the current between the PHY chips 11a and 11b and the ground, thereby limiting the bias current of the PHY chips 11a and 11b.

  In the first embodiment, the bias current limiting resistor 91b when the ECO mode selection switch 6 is selected in the normal mode is mounted with a resistance value defined in the PHY chips 11a and 11b. This is because the resistance value of the bias current limiting resistor 91b cannot be changed when the normal mode is selected in order to guarantee a signal amplitude level compliant with the IEEE 802.3 standard.

  When the ECO mode selection switch 6 is selected to the ECO mode, the resistance value of the bias current limiting resistor 91b cannot be changed, but the resistance value of the bias current limiting resistor 91c is the length of the network cables 4a and 4b. It is possible to vary the degree of restriction. By increasing the resistance value of the bias current limiting resistor 91c, the length of the network cables 4a and 4b can be shortened, and the power consumption of the PHY chips 11a and 11b can be reduced. Thus, the degree of power consumption of the switching hub 1 can be controlled in accordance with the lengths of the network cables 4a and 4b.

(Transmission signal level waveform)
FIG. 4A schematically shows an actually measured waveform of the transmission signal level of the PHY chip when the switching hub is set to the normal mode. FIG. 4B schematically shows an actually measured waveform of the transmission signal level of the PHY chip when the switching hub is set to the ECO mode. In these figures, the horizontal axis represents time (μS), and the vertical axis represents voltage value (V). The signal transmission speed at the time of measurement is, for example, 1 Gbps.

  FIG. 4A is an example of an actual measurement waveform of the transmission signal level of the PHY chips 11a and 11b when the switching hub 1 is set to the normal mode, and is a signal transmission waveform conforming to the IEEE 802.3 standard.

  FIG. 4B is an example of an actually measured waveform of the transmission signal level of the PHY chips 11a and 11b when the switching hub 1 is set to the ECO mode, and the length of the network cables 4a and 4b is limited to 50 m. It is a signal transmission waveform. The signal transmission waveform shown in FIG. 4 (b) is obtained only by reducing the amplitude level of the transmission signal of the PHY chips 11a and 11b as compared with the signal transmission waveform shown in FIG. 4 (a) conforming to the IEEE 802.3 standard. Yes, the shape and quality of the transmitted signal has not been transformed or changed. As apparent from FIG. 4B, it can be seen that the normality of transmission / reception in the ECO mode of the switching hub 1 can be guaranteed.

  Considering the actual network environment, by setting the ECO mode corresponding to the cable length, the internal bias current of the PHY chips 11a and 11b is limited to reduce the amplitude of the transmission signal, and the internal circuit of the PHY chips 11a and 11b. Power consumption can be suppressed. The power saving effect of the ECO mode is the power consumption in the normal mode corresponding to the network cable of 100m, which is the maximum cable length compliant with the IEEE 802.3 standard, and the power consumption in the ECO mode in which the cable length is limited to 50m. About 20% power reduction.

  In the illustrated example, when the ECO mode selection switch 6 is opened (OFF), the mode is switched to the ECO mode, and when the ECO mode selection switch 6 is closed (ON), the normal mode is set. Although the circuit configuration is illustrated, the present invention is not limited to this. For example, when the ECO mode selection switch 6 is closed (ON), the ECO mode selection switch 6 is switched to the ECO mode selection switch 6 and the ECO mode selection switch 6 is opened ( Of course, it is possible to use a circuit configuration for setting the normal mode state when it is set to OFF.

(Effects of the first embodiment)
According to the switching hub 1 which is the said 1st Embodiment, the following various effects are acquired.
(1) Less circuit components for power saving and no need to perform special software control. Low cost, simple configuration and power saving according to the length of the network cable. can do.
(2) In general, in a network system to which, for example, a network device compliant with the IEEE 802.3 standard is applied, it is necessary to consider attenuation in a network cable compliant with the IEEE 802.3 standard. Set according to the maximum cable length. A network cable shorter than the maximum cable length of the network cable outputs a transmission signal with an amplitude larger than necessary.
In the power saving system in FIG. 1, the switching hub 1 operates in the ECO mode state and corresponds to the cable length of the network cables 4a and 4b connected between the switching hub 1 and the lower terminal devices 2a and 2b. Since a transmission signal having an amplitude is output, it is possible to prevent a transmission signal having an amplitude larger than necessary from being output, and no extra power is consumed.
(3) When connecting to the lower terminal devices 2a and 2b, the network cables 4a and 4b can be shortened, so that the drive current required for transmission to the lower terminal devices 2a and 2b can be saved. It is possible to reduce the power consumption of the switching hub 1.
(4) When switching the switching hub 1 to the ECO mode, the bias current limiting resistor is controlled to limit the bias current inside the PHY chips 11a and 11b, thereby realizing the power saving effect while guaranteeing the normality of transmission and reception. It becomes possible to do.
(5) In addition to enabling switching to the ECO mode corresponding to a plurality of cable lengths, the cable length is not limited (for example, corresponding to the maximum cable length of 100 m in conformity with the IEEE 802.3 standard) Switching to the mode is also possible.
(6) In an actual network environment, the distance between the switching hub 1 and the lower-level terminal devices 2a and 2b installed in the same area is short, and between the higher-level device 3 installed in another area When the distance is long, it is possible to realize a power saving effect by using the switching hub 1 according to the first embodiment, and an environment-friendly power saving system can be obtained.

[Modified example of bias current control switching unit]
The switching hub 1 configured as described above has a maximum value of the bias current control switching units 9a and 9b so as to operate with a maximum cable length of 100 m or less, for example, a short cable length of 50 m, for example, conforming to the IEEE 802.3 standard. Although the description has been given of the configuration in which it is possible to select from the correspondence of the cable length of 100 m to the correspondence of the cable length of 50 m and the operation mode is switched to the two operation modes of the ECO mode and the normal mode, the present invention is not limited to this. . In the present invention, for example, by adopting a multi-stage ECO mode selection method according to various cable lengths, the values of the bias current control switching units 9a and 9b can be selected in multiple stages. .

  When the ECO mode selection switch 6 is selected to the normal mode, the switching hub 1 enters the normal mode state as described above, and does not limit the bias current of the PHY chips 11a and 11b. In this case, the amplitude level of the transmission signal of the PHY chips 11a and 11b is set in conformity with the IEEE 802.3 standard, and the length is set to IEEE 802 via the insulating pulse transformers 15a and 15b and the transmission / reception terminals 17a and 17b. .3 is connected to the lower-level terminal devices 2a and 2b via network cables of various lengths that can be connected up to a maximum of 100 m defined in the standard 3, and can communicate.

  Considering the actual network environment and needs of the user in the switching hub 1, the cable length is selected from a plurality of ECO modes for the lower ports P1 and P3 that are uplinked to the lower terminal devices 2a and 2b such as personal computers. The ECO mode can be selected in accordance with When the user's usage is changed, the lower ports P1 and P3 used in the ECO mode can be switched to the normal mode. By appropriately selecting the ECO mode selection switch 6 to the ECO mode or the normal mode in accordance with the actual use of the switching hub 1, it is possible to use a network cable having a cable length of a maximum of 100 m specified in the IEEE 802.3 standard, for example. It becomes.

  An ECO mode that matches the cable length can be selected from a plurality of ECO modes that correspond to a plurality of cable lengths, and can be switched to a normal mode that corresponds to the maximum cable length conforming to, for example, the IEEE 802.3 standard. In addition to making it possible to save power according to the length, for example, all the ports can be used as a device that supports the maximum cable length in conformity with the IEEE 802.3 standard.

[Second Embodiment]
Next, an example of power saving means in the second embodiment will be described with reference to FIGS. 1 and 2. The power saving means includes the power saving means according to the first embodiment, a communication display LED 8 that is a communication display unit for confirming a communication state, and an LED VIEW selection switch 7 that is a communication display switch. ing.

  As the LED VIEW selection switch 7, for example, a toggle type switch can be used. When the ECO mode selection switch 6 is selected to the ECO mode, the LED VIEW selection switch 7 can be validated. When the user wants to check the communication display system LED 8 of the switching hub 1, the LED VIEW selection switch 7 is selected to be in the ON state. While the user maintains the state tilted at a predetermined angle by pressing the LED VIEW selection switch 7, the display of the communication display system LED 8 according to the actual communication state (for example, “lit” at the time of linking, “flashing” at the time of the act) "If the network cable is not connected or if the link status is not established," OFF ") can be confirmed. If the user does not press the LED VIEW selection switch 7, the communication display system LED 8 is turned off.

  On the other hand, when the ECO mode selection switch 6 of the switching hub 1 is selected to the normal mode, the LED VIEW selection switch 7 is invalidated even if the user turns the LED VIEW selection switch 7 ON or OFF. The communication display system LED 8 of the hub 1 displays according to the actual communication state.

  In an actual network environment, there is no need to constantly check the communication display system LED 8. For this reason, when the switching hub 1 is operated in the ECO mode, the communication display system LEDs 8 other than the power supply display LEDs are maintained in an extinguished state, and the LED VIEW selection switch 7 is used only when it is desired to check the communication state or the like. Since the function of the communication display system LED 8 is made to work by using the LED, it is possible to reduce the energy consumption due to the LED emission. Thereby, the power consumption of the switching hub 1 can be reduced. By turning off the communication display system LED 8 of the switching hub 1, it is possible to obtain a power reduction effect of about 2%.

(Effect of the second embodiment)
According to the switching hub 1 according to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.
(1) When the ECO mode selection switch 6 of the switching hub 1 is selected to the ECO mode, in addition to limiting the bias current of the PHY chips 11a and 11b as in the first embodiment, the switching hub 1 The power consumption of the switching hub 1 can be further suppressed by turning off all communication display LEDs 8 related to communication other than the power supply display LED that displays the power supply status of the power supply.

[Third Embodiment]
Furthermore, an example of power saving means in the third embodiment will be described with reference to FIGS. 1 and 2. In the first embodiment, the single ECO mode selection switch 6 is provided for the two lower ports P1, P3 (transmission / reception terminals 17a, 17b). However, the present invention is limited to this. For example, the ECO mode selection switch 6 can be individually provided in each of the ports P1 and P3 (transmission / reception terminals 17a and 17b). It goes without saying that the ECO mode selection switch 6 can be individually provided in the other ports P2, P4 to P7. Even in the third embodiment, the communication display system LED 8 and the LED VIEW selection switch 7 according to the second embodiment can be provided.

(Effect of the third embodiment)
According to the switching hub 1 according to the third embodiment, the following effects can be obtained in addition to the effects of the first and second embodiments.
(1) The ECO mode can be individually set according to the cable length to be used, and can be sufficiently adapted to the actual network environment and needs of the user.

[Fourth Embodiment]
Further, an example of the power saving means in the fourth embodiment will be described with reference to FIGS. 1 and 2. When there is an empty port in the lower port and the upper port, a significant power reduction effect can be obtained by using an auto power save function, which is one of the inherent power saving methods of the LSI chip. Although the ECO mode selection switch 6 is selected as the ECO mode or the normal mode, the auto power save function which is a unique function of the PHY chips 11a, 11b, and 12 can be used together.

  Immediately after the switching hub 1 is powered on, the internal register of the switching chip (MAC: media access control, LSI chip) 13 is set by the LSI internal function setting ROM 14, and the auto power save function of the PHY chips 11a, 11b, 12 is enabled. Can be set to When the auto power saving function of the PHY chips 11a, 11b, and 12 is enabled, the network cables 4a and 4b between the switching hub 1 and the lower terminal devices 2a and 2b, or the network between the switching hub 1 and the upper device 3 When the cable 5 is not connected, and when the lower terminal device 2a, 2b or the upper device 3 is powered down, the auto of the PHY chips 11a, 11b, 12 corresponding to the unused lower ports and upper ports in the switching hub 1 Power save function is activated.

  At this time, unused lower ports and upper ports of the switching hub 1 enter an auto power save state, and a link signal detection circuit and a management serial interface (not shown) provided in the PHY chips 11a, 11b, and 12 ( For example, only MDIO / MDC) becomes active, and power consumption of the PHY chips 11a, 11b, and 12 can be suppressed.

  Further, in the auto power save state, the WAKE-UP signal (for example, FLP “First Link Pulse Pulse” is periodically (several seconds apart) in order to monitor the connection state of the lower-level terminal devices 2a and 2b and the higher-level device 3 that are connection counterpart devices. ”Signal and NLP“ Normal Link Pulse ”signal) to monitor the presence or absence of the connected device. Once the connected device is detected, the auto power save state is canceled and the normal operation state is restored. In this way, by using the auto power save function that is a unique function of the PHY chips 11a, 11b, and 12 together, when there is an unused port in the switching hub 1, the consumption of the PHY chip corresponding to the unused port. Electric power can be reduced by about 15%.

(Effect of the fourth embodiment)
The combination of the auto power saving function of the power saving means according to the fourth embodiment and the function of the power saving means according to the first to third embodiments, and the power saving by selecting these functions. Can be effectively achieved.

  As is clear from the above description, in each of the above-described embodiments, the configuration of the transmission technique of the IEEE 802.3 standard is exemplified, but the present invention is not limited to this. For example, the present invention can be applied to other transmission technologies other than the IEEE 802.3 standard, for example, and the initial object of the present invention can be sufficiently achieved. Therefore, the present invention is not limited to the above embodiments and modifications, and various design changes can be made within the scope described in each claim.

It is the schematic which shows one structural example of the power saving system using the switching hub with an ECO mode function which is typical embodiment of this invention. It is an operation | movement block diagram of the switching hub in FIG. FIG. 3 is a diagram schematically showing a configuration example of an internal circuit of a bias current control switching unit in FIG. 2. (A) is a figure which shows typically the measured waveform of the transmission signal level of a PHY chip when a switching hub is set to a normal mode, (b) is the transmission of a PHY chip when a switching hub is set to an ECO mode. It is a figure which shows typically the measured waveform of a signal level.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switching hub 2a, 2b Lower terminal apparatus 3 Upper apparatus 4a, 4b, 5 Network cable 6 ECO mode selection switch 7 LED VIEW selection switch 8 Communication display system LED
9a, 9b Bias current control switching unit 10 Bias current control units 11a, 11b, 12 PHY chip 13 Switching chip 14 LSI internal function setting ROM
15a, 15b, 16 Insulating pulse transformers 17a, 17b, 18 Transmission / reception terminals 90a Control signal buffer unit 91 Bias current switching unit 91a Switching FET switches 91b, 91c Bias current limiting resistors P1 to P7 Lower port P8 Upper port

Claims (1)

A network device connected to a host device and a plurality of lower terminal devices via a network cable,
A plurality of power saving mode selection switches for switching between the power saving mode and the normal mode;
A bias current control switching unit that controls bias currents of a plurality of LSI chips for communication control according to the selection of the power saving mode;
A plurality of transmission terminals that output transmission signals of a transmission level based on power consumption in the power saving mode,
The bias current control switching unit is configured to transmit the transmission level based on a power consumption mode to which each of the plurality of lower terminal devices corresponds to a predetermined length of a network cable connected to each of the plurality of lower terminal devices. A network device characterized by controlling a bias current of a corresponding LSI chip so that a signal can be received .

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