JP6080197B2 - IP phone power consumption reduction method, IP phone using the method, and IP phone system - Google Patents

Description

  The present invention relates to a method for reducing power consumption of an IP (Internet Protocol) telephone, and an IP telephone and an IP telephone system using the method.

  Conventionally, an IP telephone used in a private telephone system such as a PBX system or a button telephone system has to be kept in a normal state so that it can always receive incoming calls regardless of usage conditions. Therefore, for example, in the office environment, standby power consumption similar to that in the normal time is consumed even at night and on holidays where the frequency of use is extremely low compared to normal (weekday daytime, etc.).

  Since IP telephones must always respond to incoming calls with a short delay time, they cannot be put into a sleep state that takes time to recover. For this reason, it was necessary to keep most of the functions operable even at night when the frequency of use is low.

  Some IP telephones had a sleep function, but they could only reduce power by a small amount, such as reducing the brightness of the LEDs or making the screen a screen saver.

  By implementing EEE (Energy Efficient Ethernet (registered trademark)) specified in the IEEE 802.3az standard, it is possible to reduce the power of the physical layer (also referred to as PHY) when there is no data transmission. In a device with a short allowable delay time such as a telephone, the IP telephone main body cannot be put into a sleep state in conjunction with the EEE idle state.

JP 2011-199470 A JP2011-049894A JP 2009-147503 A JP 2009-088833 A

  An object of the present invention is to enable a significant reduction in power consumption in an IP telephone that has been difficult to reduce in power consumption.

  In order to achieve the above object, a method of the present invention is a power consumption reduction method for a plurality of IP telephones connected to a network, except that at least one of the plurality of IP telephones is in an idle state. If it is detected that the mobile phone has shifted to the sleep mode, the mobile phone includes a step of shifting its own telephone body to the sleep state.

  Further, the IP telephone system of the present invention is a plurality of IP telephones connected to the network, and when the transition to the sleep state is permitted, when detecting that the network has transitioned to the idle state, If the telephone body itself is shifted to the sleep state and the transition to the sleep state is not permitted, the plurality of IP phones that maintain the normal state and at least one of the plurality of IP phones are in the sleep state An IP telephone control device that does not permit the transition to the above, but permits others.

  In addition, the IP telephone of the present invention is an IP telephone connected to a network, and when the transition to the sleep state is permitted, when detecting that the network has transitioned to the idle state, When the main body is shifted to the sleep state and the shift to the sleep state is not permitted, the normal state is maintained.

  The IP telephone control device of the present invention permits at least one of the plurality of IP telephones connected to the network to shift to the sleep state when detecting that the network has shifted to the idle state. Without permission, other IP phones are allowed.

  The program of the present invention is a power consumption reduction program for an IP telephone connected to a network. When the computer is permitted to enter a sleep state, the network has entered an idle state. Is detected, it shifts its own telephone body to the sleep state, and realizes a function of maintaining the normal state when the transition to the sleep state is not permitted.

  Another program of the present invention is a power consumption reduction program for a plurality of IP telephones connected to a network, wherein at least one of the plurality of IP telephones is in an idle state. When the transition is detected, the transition to the sleep state is not permitted, and a function for permitting other IP telephones is realized.

  According to the present invention, power consumption can be drastically reduced in an IP telephone which has been difficult to reduce power consumption.

It is a block diagram which shows the structure of the IP telephone system by embodiment of this invention. 2 is a flowchart of a method for reducing power consumption of an IP telephone, which is executed in the IP telephone system of FIG. 6 is another flowchart of the power consumption reduction method for the IP telephone executed in the IP telephone system of FIG. 6 is still another flowchart of a method for reducing power consumption of an IP telephone, which is executed in the IP telephone system of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, a description is given using a device compliant with the IEEE 802.3az standard, but this is an example, and the present invention is not limited to a specific standard.

  First, EEE (Energy Efficient Ethernet (registered trademark)) standardized as the IEEE 802.3az standard will be briefly described. The EEE power saving mechanism is to reduce the power consumption of the Ethernet (registered trademark) equipment when the network traffic is low. LPS (Low Power Idle), which stops some of the data link layer functions when data stops flowing, or reduces power consumption by controlling the physical layer chip when traffic decreases. There is a technique called rapid PHY selection.

  In this specification, “the network is in an idle state” means that a part or all of the functions belonging to the physical layer and the data link layer in a device connected to the network are stopped or suppressed. Such an idle state can be realized by, for example, IEEE 802.3az standard EEE. Also, in this specification, “IP phone is in sleep state” means that a part or all of its functions are stopped or suppressed for all layers including the physical layer and data link layer. Say.

  In the following embodiment, power saving control of an IP telephone is performed using the IEEE 802.3az standard in a private telephone system such as a PBX system or a button telephone system. For example, it is effective when there are people in the office environment, such as in the evening or on holidays, but when the number of people is considerably smaller than normal (weekday daytime, etc.). Specifically, for example, the power saving of the IP telephone system is realized by leaving one IP telephone and setting the rest of the IP telephones in the sleep state, triggered by being in an idle state in LPI.

[Description of configuration]
FIG. 1 shows a configuration of an IP telephone system that implements a power consumption reduction method according to an embodiment of the present invention. In FIG. 1, an IP telephone system 100 includes an IP telephone control device 10, an EEE-compatible network relay device 20, and EEE-compatible IP telephones 30 to 33. The IP telephone control apparatus 10 is an apparatus that controls an IP telephone, an external network, and the like, such as an exchange or a SIP server. The EEE-compatible network repeater 20 is a device used for connecting network devices such as routers, switches, bridges, and hubs conforming to the IEEE 802.3az: EEE standard. The EEE compatible IP telephones 30 to 33 are IP telephones that comply with the IEEE 802.3az: EEE standard and include display devices such as LEDs and LCDs. In FIG. 1, four IP telephones (a) to (d) are shown, but the number is arbitrary. The IP telephones 30 to 33 and the IP telephone control apparatus 10 are connected via networks 40 and 41 such as a LAN (for example, Ethernet (registered trademark)) via the network relay device 20.

  The configuration of the IP telephone system has been described above, but since each component is well known to those skilled in the art, a detailed description of the configuration is omitted.

[Description of operation]
Next, the operation when the IP telephone system 100 of FIG. 1 implements the power consumption reduction method according to the embodiment of the present invention will be described using the flowcharts shown in FIGS.

1. Transition to sleep state (see Fig. 2)
As shown in FIG. 1, when the IP telephones (a) to (d) that support EEE and the network repeater 20 that supports EEE are connected with a LAN cable, first, whether or not each other supports EEE. Negotiation is performed between the IP telephones (a) to (d) and the network repeater 20 (step S10).

  When the negotiation is completed, the IP telephones (a) to (d) use LLDP (Link Layer Discovery Protocol) to notify the network repeater 20 of device information such as availability of EEE, port number, recovery time, etc. regarding the own telephone. (Step S12).

  The network repeater 20 uses the LLDP to determine the IP telephone control device using its own port number and the device information of the IP telephones (a) to (d) connected thereto (whether EEE support is available, port number, recovery time, etc.). 10 (step S14).

  The IP telephone control apparatus 10 confirms whether or not two or more IP telephones are connected from the device information acquired from the network repeater 20 (step S16).

  If two or more IP telephones are not connected, the process returns to step S14. If two or more IP telephones are connected, the IP telephone control apparatus 10 determines at least one, preferably one IP telephone that is not permitted to enter the sleep state from among the connected IP telephones ( Step S18). In FIG. 2, as an example, it is determined that the IP telephone set (a) cannot shift to sleep.

  The IP telephone control apparatus 10 notifies the IP telephones (b) to (d) other than the IP telephone (a) that is not permitted to enter the sleep state of permission to enter the sleep state (step S20). At this time, the IP telephone (a) that is not permitted to enter the sleep state is notified of the non-permission to enter the sleep state. Each of the IP telephones (a) to (b) stores a flag representing the transfer permission / non-permission information notified from the IP telephone control apparatus 10 in a storage device inside the telephone. When the IP telephone control device 10 is notified of permission to shift to the sleep state, the flag value is set to a value indicating permission to shift. When the IP telephone control device 10 notifies the sleep state non-permission, the flag value is set to a value indicating non-permission.

  When there is no data exchange (data transmission) between each port of the network repeater 20 and each of the IP telephones (a) to (d) connected thereto (YES in step S22), the network is idled according to the EEE standard. The state is shifted (step S24) (operation conforming to the EEE standard). Note that the transition to the network idle state by EEE can also be executed by an IP telephone (a) that is not permitted to sleep.

  When a certain network shifts to the idle state, the network relay device 20 notifies the IP telephone control apparatus 10 of information on the port that has become the idle state by LLDP (step S26).

  Each of the IP telephones (a) to (d) refers to the content of the flag storing the sleep state transition permission / non-permission information and determines whether or not it is permitted to transition to the sleep state ( Step S28). When the IP telephones (b) to (d) that are allowed to sleep (YES in step S28) detect that the network is in an idle state, the IP telephones (b) to (d) shift themselves to the sleep state (step S30). As a result, functions other than the PHY that is idle in EEE and some or all of the applications are also stopped, and power consumption is reduced.

  The IP telephones (b) to (d) having entered the sleep state notify the user by displaying the sleep state on the display device (step S32).

  The IP phone (a) that is not permitted to sleep (No in step S28) is maintained in the normal state (step S34).

2. Incoming in sleep mode (see Figure 3)
When the IP telephones (b) to (d) are in the sleep state (step S40), if there is an incoming call (YES in step S42), the IP telephone control apparatus 10 confirms the destination (step S44), and the destination IP telephone is It is confirmed whether or not the sleep state is set (step S46). At this time, for example, the IP telephone control apparatus 10 determines whether or not the destination IP telephone is in a sleep state based on information on whether or not the destination network is in an idle state and information on whether or not the destination IP telephone is allowed to sleep. to decide.

  When the destination of the incoming call is an IP telephone (a) that is not permitted to sleep, the IP telephone control device 10 sends a notification of the incoming call to the destination as usual (step S48), and the destination IP telephone (a) receives the incoming call. An operation is performed (step S50) (normal operation).

  When the destination of the incoming call is the sleep state IP telephone (x) (x is b, c, or d), the IP telephone control apparatus 10 first transmits data for notifying the destination IP telephone (x) of the incoming ( Step S52).

  The incoming call notification data is sent to the destination IP telephone (x) through the network repeater 20, whereby the network in the meantime is restored from the idle state to the active state (operation conforming to the EEE standard). Then, when the destination IP phone (x) detects that the network is in the active state, it starts recovery from the sleep state (step S54).

  The IP telephone control device 10 transfers the incoming call to the IP telephone (a) that is not permitted to sleep, as a proxy until the destination IP telephone (x) recovers from the sleep state (step S56). At this time, if there are two or more IP telephones permitted to enter the sleep state, the IP telephone control apparatus 10 selects one and transfers the incoming call. For example, the incoming call may be forwarded to the highest priority assigned to each IP telephone in advance among the IP telephones permitted to migrate.

  The proxy IP phone (a) to which the incoming call has been transferred starts the incoming call operation, and at the same time, displays the proxy incoming call on the display device and notifies the user (step S58).

  When the proxy IP phone (a) is performing an incoming call operation, if the user responds to the proxy IP phone (a) (YES in step S60), the call is started as it is (step S62). .

  When the original destination IP telephone (x) recovers from the sleep state to the normal state in a state where there is no response at the proxy IP telephone (a), the destination IP telephone (x) notifies the IP telephone control device 10 of the completion of recovery. (YES in step S64).

  When receiving the restoration completion notification, the IP telephone control device 10 transfers the incoming call to the destination IP telephone (x) and cancels the incoming call from the proxy IP telephone (a) (step S66).

  The destination IP telephone (x) performs an incoming call operation (step S68), and if there is a response from the user (YES in step S70), the telephone call is started (step S72).

3. Telephone operation in sleep mode (see Figure 4)
When the user performs some operation such as pressing a dial button on the sleepy IP telephones (b) to (d) and the IP telephone detects this operation (step S82), the IP telephone (x) (x is b) Or c or d) starts recovery from the sleep state (step S84).

  During restoration, the IP telephone (x) notifies the user by displaying that the restoration is in progress on the display device (step S86).

  When the restoration is completed (step S88), the IP telephone (x) notifies the IP telephone control device 10 that it has recovered from the sleep state (step S90). This is because data is transmitted from the IP telephone set (x) to the network repeater 20, and by this operation, the idle network between the network repeater 20 and the IP telephone set (x) is made active. Are also performed simultaneously (operation conforming to the EEE standard).

  When the restoration is completed, the IP telephone (x) displays on the display device that the restoration is completed, and notifies the user that the normal state has been restored (step S92). After restoration, the IP telephone (x) performs a normal operation in response to an operation from the user.

  As described above, in the above embodiment, (i) the IP telephone control device that controls the IP telephone recognizes the state of the subordinate IP telephone using LLDP from the network relay, and (ii) the IP telephone When the PHY becomes idle due to EEE, the PHY state is detected and the device itself goes into the sleep state to reduce power consumption. However, at least one of the IP telephones in the entire system maintains the normal state, and (iii) When an incoming call is received by the IP telephone, the IP telephone control device transmits data notifying the incoming call to the target IP telephone. When the target telephone is in the sleep state, until the normal state is restored from the sleep state. Since the incoming call cannot be received during this time, the incoming call is transferred to the IP phone that has been in the normal state, and (iv) the destination IP phone starts the call. If target phone before is restored to the normal state, return call to the target phone.

The above embodiment has the following advantages.
-In addition to reducing the power consumption of PHY by EEE, the power consumption of the IP phone body can be reduced.
Notification of information such as device status between devices can be easily realized by using LLDP used in EEE.
By putting the IP telephone in the sleep state in accordance with the idle state of the EEE, it is not necessary to newly generate and control a state change trigger.
-An IP telephone with a strict delay time for transmitted data can be put into a sleep state with a long recovery time without mounting an additional buffer or the like.

  As described above, the present embodiment has the following effects.

  The first effect is that it is possible to shift to a sleep state with a long recovery time in an IP telephone that is required to always respond with a short delay time to incoming data such as incoming calls. The power consumption can be reduced.

  The second effect is that incorporation and control into the system can be easily performed by using standardized EEE.

  The third effect is that no hardware change or addition is required for the existing system.

  The IP telephone, the IP telephone control device, and the IP telephone system described above can be realized by hardware, software, or a combination thereof. The power consumption reduction method performed by the IP telephone, the IP telephone control device, or the IP telephone system can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

  The program may be stored using various types of non-transitory computer readable media and supplied to the computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD- R, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A method for reducing power consumption of a plurality of IP telephones connected to a network, wherein at least one of the plurality of IP telephones is excluded and the main body of the telephone is put into sleep when detecting that the network has shifted to an idle state. A method for reducing power consumption, including a step of shifting to a state.

(Appendix 2)
A step of allowing at least one of the IP telephones to not allow the transition to the sleep state and permitting the rest, and causing the IP telephones that are permitted to enter the sleep state to perform the transition The power consumption reduction method according to appendix 1, wherein:

(Appendix 3)
When an incoming call to an IP phone that is in a sleep state is detected, the IP phone starts to recover from the sleep state, forwards the incoming call to an IP phone that is not in the sleep state, and the recovery is completed before the call at the transfer destination starts Then, the power consumption reduction method according to appendix 1 or 2, further comprising a step of changing the forwarding destination of the incoming call to the restored IP telephone.

(Appendix 4)
The power consumption reduction method according to any one of appendices 1 to 3, further comprising a step of starting recovery from the sleep state when the IP phone in the sleep state detects a telephone operation from a user.

(Appendix 5)
The power consumption reduction method according to any one of appendices 1 to 4, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

(Appendix 6)
When a plurality of IP telephones connected to the network are allowed to enter the sleep state, when detecting that the network has entered the idle state, the own telephone body is caused to enter the sleep state. A plurality of IP phones that maintain a normal state when the transition to the sleep state is not permitted;
An IP telephone control device that does not permit at least one of the plurality of IP telephones to enter the sleep state, and permits the rest;
An IP telephone system.

(Appendix 7)
When the IP telephone control device detects an incoming call to the IP telephone in the sleep state, the IP telephone control device causes the IP telephone to start recovery from the sleep state, forwards the incoming call to the IP telephone not in the sleep state, and makes a call at the transfer destination. The IP telephone system according to appendix 6, wherein if the restoration is completed before the start, the transfer destination of the incoming call is changed to the restored IP telephone.

(Appendix 8)
The IP telephone system according to appendix 6 or 7, wherein the plurality of IP telephones start recovery from a sleep state when detecting a telephone operation from a user when the plurality of IP telephones are in a sleep state.

(Appendix 9)
The IP telephone system according to any one of appendices 6 to 8, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

(Appendix 10)
A network relay device connected to the network is further provided, and information communication is performed using LLDP between the network relay device and the plurality of IP telephones or the IP telephone control device. 10. The IP telephone system according to any one of 9 above.

(Appendix 11)
11. The IP telephone system according to appendix 10, wherein the network repeater notifies the IP telephone control device when the network is in an idle state.

(Appendix 12)
If the IP phone is connected to the network and the transition to the sleep state is permitted, when detecting that the network has transitioned to the idle state, the mobile phone itself transitions to the sleep state and sleep An IP phone that maintains a normal state when transition to a state is not permitted.

(Appendix 13)
The IP telephone controller grants permission to enter the sleep state, and the IP telephone controller does not allow at least one of the IP telephones to enter the sleep state, and permits the others. The IP phone according to appendix 12, characterized by:

(Appendix 14)
When the IP telephone control device detects an incoming call to the IP telephone in the sleep state, if (i) itself is not in the sleep state, it receives an incoming call transferred from the IP telephone control device, and (ii) itself sleeps. If the IP telephone control device instructs the recovery from the sleep state when in the state, the recovery from the sleep state is started, and before the call of the other IP telephones that are not in the sleep state that received the incoming call, 14. The IP phone according to appendix 13, wherein when the restoration is completed, the incoming call is forwarded to itself.

(Appendix 15)
15. The IP telephone set according to any one of appendices 12 to 14, wherein when the telephone operation from the user is detected in the sleep state, recovery from the sleep state is started.

(Appendix 16)
The IP telephone set according to any one of appendices 12 to 15, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

(Appendix 17)
At least one of the plurality of IP telephones connected to the network is not permitted to enter the sleep state when it detects that the network has entered the idle state, and is permitted to other IP telephones. IP phone control device.

(Appendix 18)
When an incoming call to an IP phone that is in a sleep state is detected, the IP phone starts to recover from the sleep state, forwards the incoming call to an IP phone that is not in the sleep state, and the recovery is completed before the call at the transfer destination starts Then, the IP telephone control apparatus according to appendix 17, wherein the destination of the incoming call is changed to the restored IP telephone.

(Appendix 19)
19. The IP telephone control device according to appendix 17 or 18, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

(Appendix 20)
20. The IP telephone control apparatus according to any one of supplementary notes 17 to 19, wherein device information of the IP telephone is notified based on LLDP from a network relay connected to the network.

(Appendix 21)
The IP telephone control apparatus according to appendix 20, wherein a notification that the network is in an idle state is received from the network repeater.

(Appendix 22)
A power consumption reduction program for IP telephones connected to a network,
On the computer,
When the transition to the sleep state is permitted, when detecting that the network has transitioned to the idle state, the main body of the telephone is transitioned to the sleep state, and the transition to the sleep state is not permitted. Is a power consumption reduction program that realizes the function to maintain the normal state.

(Appendix 23)
When the IP telephone controller further detects an incoming call to the IP telephone in the sleep state, (i) if the IP telephone controller is not in the sleep state, the computer receives the incoming call transferred from the IP telephone controller, and (ii) ) When the IP phone control device instructs the recovery from the sleep state when the device is in the sleep state, the recovery from the sleep state is started, and the call of the other IP phone that is not in the sleep state that received the incoming call The power consumption reduction program according to appendix 22, wherein if the restoration is completed before the start, a function of receiving an incoming call that has been transferred to itself is realized.

(Appendix 24)
24. The power consumption reduction program according to appendix 22 or 23, wherein when the telephone operation from the user is further detected in the sleep state, the computer realizes a function of starting recovery from the sleep state.

(Appendix 25)
25. The power consumption reduction program according to any one of appendices 22 to 24, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

(Appendix 26)
A power consumption reduction program for a plurality of IP telephones connected to a network,
On the computer,
At least one of the plurality of IP telephones has a function that does not allow a transition to a sleep state when it detects that the network has transitioned to an idle state, and permits other IP telephones. Power consumption reduction program to let you.

(Appendix 27)
When the computer further detects an incoming call to the IP phone in the sleep state, the IP phone starts to recover from the sleep state, forwards the incoming call to the IP phone that is not in the sleep state, and before the call starts at the transfer destination. 27. The power consumption reduction program according to appendix 26, wherein when the restoration is completed, the restored IP telephone is provided with a function of changing the transfer destination of the incoming call.

(Appendix 28)
28. The power consumption reduction program according to appendix 26 or 27, wherein the transition to the idle state is performed in accordance with the IEEE 802.3az standard.

10 IP telephone control device 20 Network relay machine 30 IP telephone (a)
31 IP phone (b)
32 IP phone (c)
33 IP phone (d)
40 LAN
41 LAN

Claims (7)

A method for reducing power consumption of a plurality of IP telephones connected to a network,
Excluding at least one of the plurality of IP telephones, and detecting that the network has transitioned to an idle state, transitioning its own telephone body to a sleep state ;
When the IP telephone control device detects an incoming call to the IP telephone in the sleep state, the IP telephone control apparatus starts recovery from the sleep state, transfers the incoming call to the IP telephone not in the sleep state, and starts a call at the transfer destination If the restoration is completed before, the step of changing the forwarding destination of the incoming call to the restored IP phone;
Power consumption reduction method. The IP telephone control device further includes a step of permitting at least one of the IP telephones not to allow the transition to the sleep state, and permitting the rest, to the IP telephone that is permitted to enter the sleep state The method for reducing power consumption according to claim 1, wherein the step of shifting is executed. 3. The power consumption reduction according to claim 1, further comprising a step of starting recovery from the sleep state when the IP phone in the sleep state detects a telephone operation from a user. 4. Method. The power consumption reduction method according to any one of claims 1 to 3 , wherein the transition to the idle state of the network is performed in accordance with the IEEE 802.3az standard. When a plurality of IP telephones connected to the network are allowed to enter the sleep state, when detecting that the network has entered the idle state, the own telephone body is caused to enter the sleep state. A plurality of IP phones that maintain a normal state when the transition to the sleep state is not permitted;
An IP telephone control device that does not permit at least one of the plurality of IP telephones to enter the sleep state, and permits the rest;
Equipped with a,
When the IP telephone control device detects an incoming call to the IP telephone in the sleep state, the IP telephone starts to recover from the sleep state, forwards the incoming call to the IP telephone not in the sleep state, and calls at the transfer destination if the restoration before starting is completed, IP telephone system Ru place the call destination to the IP telephone restored. At least one of the plurality of IP telephones connected to the network is not permitted to enter the sleep state when it detects that the network has entered the idle state, and is permitted to other IP telephones. An IP telephone control device that
When an incoming call to an IP phone that is in a sleep state is detected, the IP phone starts to recover from the sleep state, forwards the incoming call to an IP phone that is not in the sleep state, and the recovery is completed before the call at the transfer destination starts Then, an IP telephone control apparatus that changes the forwarding destination of the incoming call to the restored IP telephone . A program for causing a computer to function as an IP telephone control device that controls a plurality of IP telephones connected to a network,
On the computer,
At least one of the plurality of IP telephones does not allow a transition to a sleep state when it detects that the network has transitioned to an idle state, and permits other IP telephones ;
When an incoming call to an IP phone that is in a sleep state is detected, the IP phone starts to recover from the sleep state, forwards the incoming call to an IP phone that is not in the sleep state, and the recovery is completed before the call at the transfer destination starts Then, a power consumption reduction program for realizing the function of changing the forwarding destination of the incoming call to the restored IP telephone .