JP2023025771A - Private branch exchange and simultaneous calling method - Google Patents

Abstract

To provide a private branch exchange and a simultaneous calling method for avoiding the unresponsiveness at the time of simultaneous calling to a plurality of extension telephones having an incoming call rejection function.SOLUTION: The private branch exchange comprises: a simultaneous calling unit which makes simultaneous calling to a plurality of extension telephones; a storage unit which stores incoming call acceptance information indicating which one of an incoming call rejection mode and a normal mode each of the plurality of extension telephones operates and a prescribed threshold; and a simultaneous calling management unit which counts the number of extension telephones operating in the normal mode among the plurality of extension telephones on the basis of the incoming call acceptance information stored in the storage unit when a change permission request signal transmitted from an extension telephone is received, transmits a permission signal to an extension telephone of a transmission source and changes contents of the incoming call acceptance information corresponding to the extension telephone of the transmission source to the incoming call rejection mode when the number of extension telephones is more than the threshold, and transmits a rejection signal for rejecting the change request by the change permission request signal to the extension telephone of the transmission source when the number of extension telephones is equal to or less than the threshold.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a private branch exchange and a general call method using a private branch exchange for making a general call to a plurality of extension telephones in response to an incoming call.

A telephone exchange as a private branch exchange is connected to a plurality of extension telephones having an extension line function, and calls a corresponding extension telephone in response to an incoming call from an outside line, an extension line, or a dedicated line.

In addition, as such a telephone exchange, there has been proposed a telephone exchange equipped with a simultaneous calling function that calls a plurality of extension telephones all at once when the telephone number of the destination of the incoming call by an outside line is a main number or a group number (for example, , see Patent Document 1). As a result, even if the person in charge of the extension phone intends to answer the call but is unable to answer the call immediately for some reason, the extension that received the call will be able to It becomes possible to answer by telephone.

Furthermore, the extension telephone described in Patent Document 1 is equipped with an incoming call rejection function capable of setting an incoming call rejection state in preparation for when the user cannot answer (for example, when going out or during a meeting).

JP 2014-49914 A

However, there is a problem that if all the extension telephones operate in the state of rejection of incoming calls, it becomes impossible to answer incoming calls even though they are calling all at once.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a private branch exchange and a general calling method capable of avoiding non-response when making a general call to a plurality of extension telephones having an incoming call rejection function.

A private branch exchange according to the present invention is a private branch exchange connected to a plurality of extension telephones operating in a normal mode in which an incoming call is possible or in an incoming call rejection mode in which an incoming call is rejected. An all-calling unit that makes all-out calls, a storage unit that stores a predetermined threshold value, information indicating whether each of the plurality of extension telephones operates in the call rejection mode or the normal mode, and a predetermined threshold. and, when a change permission request signal requesting permission to change from the normal mode to the call rejection mode is received from each of the plurality of extension telephones, the call acceptability stored in the storage unit is received. counting the number of extension telephones operating in the normal mode among the plurality of extension telephones based on the information, and if the number of extension telephones is greater than the threshold value, sending a permission signal to the extension telephone that has transmitted the change permission request signal; and change the content of the incoming call permission/prohibition information corresponding to the extension telephone of the transmission source to the incoming call rejection mode, and if the number of telephones is equal to or less than the threshold, a change permission request is issued by the change permission request signal. and a general call management unit that transmits a rejection signal to the extension telephone of the transmission source.

In addition, the private branch exchange according to the present invention includes first to n-th (n is an integer of 2 or more) incoming call groups each including a plurality of extension telephones operating in a normal mode capable of receiving an incoming call or an incoming call rejection mode for rejecting an incoming call. a general call section for making a general call to the plurality of extension telephones included in one of the first to n-th groups in response to an incoming call; to n-th groups, and indicating whether each of the plurality of extension telephones included in the group operates in the call rejection mode or the normal mode; receiving a change permission request signal requesting permission to change from the normal mode to the incoming call rejection mode transmitted from each of the plurality of extension telephones included in the one group; the number of extension telephones operating in the normal mode among the plurality of extension telephones is counted based on the incoming call acceptance/rejection information corresponding to the one group stored in the storage unit, and If the number is greater than the threshold value corresponding to the one group, a permission signal is transmitted to the extension telephone that is the transmission source of the change permission request signal, and the content of the incoming call permission/prohibition information corresponding to the transmission source of the extension telephone is transmitted. a general call management unit that changes to the incoming call rejection mode and transmits a rejection signal rejecting a change permission request based on the change permission request signal to the extension telephone of the transmission source when the number of telephones is equal to or less than the threshold value; , has

A general call method according to the present invention is connected to a plurality of extension telephones operating in a normal mode for receiving incoming calls or a call rejection mode for rejecting incoming calls, and each of the plurality of extension telephones operates in the call rejection mode and the normal call rejection mode. A general calling method by a private branch exchange including a storage unit storing information indicating whether or not to operate in which of the modes to operate and a predetermined threshold value, wherein the simultaneous calling method is transmitted from each of the plurality of extension telephones, When a change permission request signal requesting permission to change from the normal mode to the incoming call rejection mode is received, one of the plurality of extension phones is set to the normal mode based on the incoming call acceptability information stored in the storage unit. a first step of counting the number of extension telephones operating with a telephone; a second step of determining whether said number is greater than said threshold; and if said number is determined to be greater than said threshold, said a third step of transmitting an authorization signal to the extension telephone that is the transmission source of the change permission request signal and changing the content of the reception availability information corresponding to the extension telephone that is the transmission source to the reception rejection mode; a fourth step of transmitting a refusal signal for rejecting the change permission request by the change permission request signal to the extension telephone of the transmission source when it is determined that the change permission request signal is equal to or less than the threshold; a fifth step of making a general call to the extension telephones of
have

A private branch exchange according to the present invention calls a plurality of extension telephones operating in a normal mode or an incoming call rejection mode in response to an incoming call. , first, the number of extension telephones operating in the normal mode is counted. Then, if the number of calls is greater than a threshold representing a predetermined lower limit number of incoming calls, the extension telephone of the transmission source is changed to an incoming call rejection mode. On the other hand, if this number is equal to or less than the threshold, the change request from the transmission source extension telephone is rejected.

As a result, the number of extension telephones that are ready to receive calls (normal mode) is always equal to or greater than the predetermined lower limit number of incoming calls, so that nonresponse to incoming calls can be avoided.

1 is a block diagram showing the configuration of a private branch telephone system 100 including a private branch exchange according to the present invention; FIG. FIG. 10 is a diagram showing an example of an extension management table (initial state); 4 is a flow chart showing a procedure of general call processing; 4 is a flowchart showing the procedure of general call management processing; FIG. 10 is a diagram showing another example of an extension management table;

FIG. 1 is a block diagram showing the configuration of a private branch telephone system 100 including a private branch exchange according to the present invention.

As shown in FIG. 1, a private branch telephone system 100 is connected to a public switched telephone network NW. and groups G1, G2, G3 and G4.

Each of the incoming call groups G1 to G4 corresponds to, for example, a department or section within a company, and a dial-in number as an outside line number is assigned to each incoming call group.

For example, as shown in FIG. 1, the incoming call group G1 includes multi-function fixed extension telephones A1 and A2 wiredly connected to the private branch exchange 10, and mobile extension telephone A3 wirelessly connected to the private branch exchange 10. ~A7 and The incoming call group G2 includes multifunctional fixed extension telephones B1 to B3 wired to the private branch exchange 10 and mobile extension telephones B4 to B9 each wirelessly connected to the private branch exchange 10. The incoming call group G3 includes multifunctional fixed extension telephones C1 and C2 that are wire-connected to the private branch exchange 10, and mobile extension telephones C3 to C9 that are wirelessly connected to the private branch exchange 10, respectively. The incoming call group G4 includes multi-function fixed extension telephones D1 to D3 wiredly connected to the private branch exchange 10, and mobile extension telephones D4 to D8 each wirelessly connected to the private branch exchange 10.

Each of the mobile extension telephones A3 to A7, B4 to B9, C3 to C9, and D4 to D8 is, for example, a communication terminal receiving FMC (Fixed-Mobile Convergence) service provided by a mobile carrier, or an extension application installed. It is a communication terminal that can be used as an extension line of the private branch exchange 10, such as a smart phone that has been registered.

Each of the mobile extension telephones A3-A7, B4-B9, C3-C9, and D4-D8 operates in a "normal mode" in which it is possible to receive general calls from the private branch exchange 10 in the initial state. It has an incoming call rejection function that can be changed to "incoming call rejection mode" that rejects incoming calls by operation etc. For example, when an instruction to change from the normal mode to the incoming call rejection mode is given by the user's operation of the special number, the portable extension telephone that receives the instruction transmits a change permission request signal to the private branch exchange 10 . At this time, when a permission signal indicating permission to change to the incoming call rejection mode is received as a reply from the private branch exchange 10, the mobile extension phone that is the sender of the change permission request signal (hereinafter referred to as the mobile extension phone of the sender) ) is set to operate in an incoming call rejection mode for rejecting incoming calls for general calls.

On the other hand, when receiving a refusal signal as a reply from the private branch exchange 10, the mobile extension phone of the sender does not change to the incoming call refusal mode and maintains the normal mode state. Also, in response to the rejection signal, the mobile extension phone of the transmission source performs display or voice output to notify the user that the change to the call rejection mode was not possible. Further, during this period, the mobile extension telephones operating in the call rejection mode among the mobile extension telephones belonging to the call reception group receive the call rejection cancellation request signal sent from the private branch exchange 10 to prompt the user to cancel the call rejection mode. . The mobile extension phone that has received the call rejection cancellation request signal performs display or voice output prompting the user to cancel the call rejection mode or change to the normal mode.

In addition, the portable extension telephone that has received an instruction to change from the call rejection mode to the normal mode by the user's operation of the special number or the like restores its own state from the call rejection mode to the normal mode, and transmits the call rejection release signal to the private branch exchange 10. do.

Upon receiving the change permission request signal, the private branch exchange 10 performs general call management processing. That is, the private branch exchange 10 first determines whether to permit the change from the normal mode to the incoming call rejection mode or reject the request for the change. Here, when it is determined to permit, the private branch exchange 10 manages the portable extension telephone that is the transmission source of the change permission request signal (hereinafter also referred to as the transmission source portable extension telephone) as an extension telephone in the incoming call rejection mode. On the other hand, when the private branch exchange 10 determines to reject the request to change from the normal mode to the incoming call rejection mode, the private branch exchange 10 transmits the above-described rejection signal to the mobile extension phone of the transmission source, and sets the incoming call rejection mode within the incoming call group. An incoming call rejection release request signal is transmitted to each mobile extension phone in operation. Here, when the private branch exchange 10 receives an incoming call rejection cancellation signal as a reply to the incoming call rejection cancellation request signal, it manages the mobile extension telephone that has sent the incoming call rejection cancellation signal as an extension telephone in the normal mode. .

Further, when the private branch exchange 10 receives an incoming call from an outside line from the public line network NW, it selects a plurality of mobile extension telephones and fixed extensions belonging to the incoming group corresponding to the outside line number (dial-in number) among the incoming groups G1 to G4. All-out call processing is performed to make calls to telephones all at once.

The private branch exchange 10 includes a storage device 30 in which an extension management table is stored, and a control section 31 that executes the general call management processing and general call processing described above.

FIG. 2 is a diagram showing an example of an extension management table.

As shown in FIG. 2, in the extension line management table, each of the incoming groups G1 to G4 is associated with a dial-in number as an outside number, a fixed extension number, a mobile extension number, information on acceptance/rejection of incoming calls, and a threshold value. A lower limit number of incoming calls is indicated.

For example, in the incoming group G1, as a dial-in number, an external number "03-1234-XXX1 (X is 0 An integer of ~9)” is shown. Also, in the paging group G1, as fixed extension numbers, [210] and [211] representing the extension numbers of the fixed extension telephones A1 and A2 belonging to the paging group G1 are shown. Also, in the incoming call group G1, as the mobile extension numbers, [410], [411], [412], [413] and [414] representing the extension numbers of the mobile extension telephones A3 to A7 belonging to the incoming call group G1. It is shown.

Also, in the incoming call group G1, extension numbers [410], [411], [412], [413] and [414] are associated with each other, and the mobile extension phone corresponding to the extension number is " Incoming reception acceptance/rejection information indicating in which of the normal mode and the 'incoming rejection mode' the operation is performed is attached. In the initial state, as shown in FIG. 2, all the extension numbers of the mobile extension telephone are attached with incoming call acceptability information representing the normal mode.

Furthermore, in the incoming call group G1, among the five mobile extension telephones belonging to the incoming call group G1, the minimum number of incoming mobile extension telephones to be maintained in a state capable of receiving calls (normal mode) is as follows: For example, two are assigned.

The control unit 31 includes a general call processing unit that performs the general call processing described above and a general call management unit that performs the general call management processing.

Detailed operations of the general call processing section and the general call management section will be described in order below.
[Simultaneous call processing]
When the private branch exchange 10 receives an incoming call from the public line network NW, the general call processing unit of the control unit 31 executes the following general call processing.

FIG. 3 is a flow chart showing the procedure of general call processing.

In FIG. 3, the general call processing unit selects an incoming call group Gj (j is an integer of 1 or more) from the extension management table shown in FIG. ) (step S21).

Next, the general call processing unit makes a general call to all mobile extension numbers associated with the incoming call group Gj in the extension management table (step S22).

In this way, the general call processing unit makes a general call to a plurality of mobile extension telephones belonging to the incoming call group corresponding to the external line number (dial-in number) in response to an external line incoming call.
[Simultaneous call management process]
When the private branch exchange 10 receives the change permission request signal transmitted from the mobile extension telephones (A3 to A7, B4 to B9, C3 to C9, D4 to D8), the general call management section of the control section 31 performs the following general call Perform administrative actions.

FIG. 4 is a flow chart showing the procedure of general call management processing.

In FIG. 4, the general call management unit first selects, for example, the extension line management table shown in FIG. (also called a telephone) belongs to the incoming call group Gr (r is an integer equal to or greater than 1) (step S12).

Next, the general call management unit acquires the minimum number of incoming calls corresponding to the incoming call group Gr from the extension management table, and sets this as the minimum incoming number Kmin (step S13).

Next, the general call management unit counts the number of mobile extension numbers indicating that the reception acceptability information corresponding to the incoming call group Gr indicates "normal mode" from the extension management table, and sets this number as the number of possible incoming calls Kc ( step S14).

Next, the general call management section determines whether or not the number Kc of incoming calls is greater than the minimum number of incoming calls Kmin (step S15). In other words, in step S15, if the number of incoming calls Kc is greater than the lower limit number of incoming calls Kmin, it is determined that the change from the normal mode to the incoming call rejection mode is permitted. It is determined to reject the change from the normal mode to the call rejection mode.

If it is determined in step S15 that the number Kc of incoming calls is greater than the minimum number of incoming calls Kmin, the general call management section transmits a permission signal to the extension number of the mobile extension phone of the transmission source (step S16). After step S16 is executed, the general call management unit changes the contents of the incoming call availability information attached to the mobile extension number of the mobile extension phone of the sender to the incoming call rejection mode, for example, in the extension management table shown in FIG. step S17). In other words, when it is determined that the change from the normal mode to the incoming call rejection mode is permitted, the general call management unit transmits a permission signal to the mobile extension phone of the transmission source and sets the mobile extension phone of the transmission source to the incoming call rejection mode. managed as an extension phone.

On the other hand, if it is determined in step S15 that the number Kc of incoming calls is equal to or less than the minimum number of incoming calls Kmin, the general call management unit transmits a rejection signal to the extension number of the mobile extension phone of the transmission source (step S18). After execution of step S18, the general call management unit transmits an incoming call rejection cancellation request signal to the extension number of each mobile extension phone operating in the call rejection mode among the group of mobile phone extension phones belonging to the incoming call group Gr (step S19). ).

In other words, when it is determined in step S15 that permission to change from the normal mode to the incoming call rejection mode is to be refused, the general call management section sends a rejection signal indicating rejection of the change to the incoming call rejection mode to the mobile extension telephone of the transmission source. Send to Further, at this time, the general call management section sends a call rejection cancellation request signal to each of the mobile extension telephones operating in the call rejection mode among the group of mobile extension telephones belonging to the call group Gr to prompt the user to cancel the call rejection mode. to send.

After executing step S17 or S19 described above, the general call management section ends the general call management process shown in FIG.

The operation performed by the general call management process shown in FIG. 4 will be described below using an example.

For example, assume that the extension management table is in the initial state as shown in FIG. At this time, as shown in FIG. 2, the minimum number of incoming calls Kmin corresponding to the incoming call group G1 is 2, and according to the reception acceptability information corresponding to the incoming call group G1 in the initial state, the mobile phones in the normal mode state The number of extension telephones, that is, the number of incoming telephones Kc is five. Therefore, since the number of incoming calls Kc is greater than the minimum number of incoming calls Kmin, the general call management unit permits the incoming call rejection setting request, and sends a permission signal to that effect to the mobile extension phone A4, which is the transmission source of the change permission request signal. Send (S16). Furthermore, the general call management unit changes the contents of the incoming call availability information corresponding to the extension number [411] of the mobile extension phone A4 shown in the extension management table from the normal mode to the incoming call rejection mode as shown in FIG. S17).

Further, it is assumed that the change permission request signal is subsequently wirelessly transmitted to the private branch exchange 10 from the mobile extension phone A5 belonging to the incoming call group G1. According to the reception acceptability information corresponding to the incoming call group G1 at this point, the number of mobile extension phones in the normal mode, that is, the number of incoming calls possible Kc is four. Therefore, since the number of incoming calls Kc is greater than the minimum number of incoming calls Kmin (2), the general call management section permits the incoming call rejection setting request, and calls the extension number [412] of the mobile extension phone A5 shown in the extension management table. The contents of the corresponding incoming call permission/prohibition information are changed from the normal mode to the incoming call rejection mode as shown in FIG. 5 (S17).

Further, it is assumed that a change permission request signal is subsequently wirelessly transmitted to the private branch exchange 10 from the mobile extension phone A7 belonging to the incoming call group G1. According to the reception acceptability information corresponding to the incoming call group G1 at this point, the number of mobile extension phones in the normal mode, that is, the number of incoming calls Kc is three. Therefore, since the number of incoming calls Kc is greater than the minimum number of incoming calls Kmin (2), the general call management unit permits the incoming call rejection setting request, and calls the extension number [414] of the mobile extension phone A7 shown in the extension management table. The contents of the corresponding incoming call permission/prohibition information are changed to the incoming call rejection mode as shown in FIG. 5 (S17).

Further, it is assumed that a change permission request signal is subsequently wirelessly transmitted to the private branch exchange 10 from the mobile extension phone A3 belonging to the incoming call group G1. According to the reception acceptability information corresponding to the incoming call group G1 at this time, the number of mobile extension phones in the "normal mode" state, that is, the number of incoming calls possible Kc is two. Therefore, since the number Kc of incoming calls is equal to or less than the minimum number of incoming calls Kmin, the general call management section rejects the incoming call rejection setting request. At this time, the general call manager does not change to the incoming call rejection mode (S17), and transmits a rejection signal indicating rejection of the incoming call rejection setting request to the mobile extension phone A3 as the sender (S18). Furthermore, the general call management section sends an incoming call rejection cancellation request signal to each of the mobile extension telephones A3 to A7 belonging to the incoming call group G1 and operating in the incoming call rejection mode to prompt cancellation of the incoming call rejection mode. Send (S19).

That is, although the mobile extension phone A3 requests permission to change from the normal mode to the incoming call rejection mode, if the mobile extension phone A3 is operated in the incoming call rejection mode, the mobile extension phone can receive calls within the incoming call group G1. is one, which is less than two, which is the minimum number of incoming calls Kmin assigned to the incoming call group G1. Therefore, when the private branch exchange 10 makes a general call to the incoming call group G1 in response to an incoming call on the outside line, there is only one portable extension phone A6 that can answer, so there is a possibility that the answer will not be possible.

Therefore, at this time, the general call management unit always predetermines the number of mobile extension telephones that can respond to the general call by rejecting the request by the mobile extension telephone A3 to change from the normal mode to the incoming call rejection mode. Two or more, which is the set lower limit number of incoming calls (threshold), can be secured.

In the above-described embodiment, an example in which the present invention is applied to a telephone system in which a plurality of mobile extension telephones are called simultaneously in response to an incoming call from an external line has been described. Then, a telephone system that calls multiple mobile extension phones all at once by making a group call via an extension line, or dialing an incoming (extension) group number from a mobile extension phone at another location within the company, and a dedicated line It is also applicable to a telephone system in which a plurality of mobile extension telephones are called all at once by receiving a group call through the telephone system.

In the above-described embodiment, the premises telephone 10 changes to the incoming call rejection mode in response to the change permission request signal in the order of arrival. It is also possible to set the order of priority. For example, the general call management unit of the private telephone 10 assigns two levels of priority, high and low, to each mobile extension phone for each incoming call group. A refusal signal is sent to this mobile extension phone only when the priority of the mobile extension phone is low. Further, at this time, an incoming call rejection release request signal for prompting release of the incoming call rejection mode is transmitted only to the mobile extension phone operating in the incoming call rejection mode and having a low priority among the plurality of mobile extension phones belonging to the incoming call group.

In short, in the private branch exchange according to the present invention, when all of a plurality of portable extension telephones operating in the normal mode or the call rejection mode, which are capable of receiving calls, are called all at once, the change from the normal mode to the call rejection mode transmitted from the extension telephones is performed. In response to the change permission request signal requesting permission, the number of extension telephones operating in the normal mode is counted (S14). Here, if the number of calls is greater than a threshold representing a predetermined lower limit of the number of incoming calls, a permission signal is transmitted to the extension phone of the transmission source, and the content of the incoming call permission/prohibition information corresponding to the extension phone of the transmission source is set to the incoming call rejection mode. (S17). On the other hand, if this number is equal to or less than the threshold, a refusal signal for rejecting the change permission request from the extension telephone of the transmission source is transmitted to the extension telephone of the transmission source (S18).

As a result, it is possible to keep the number of extension telephones equal to or greater than the predetermined minimum number of incoming calls in a state (normal mode) capable of receiving calls at all times, so that it is possible to avoid non-response to all-out calls in response to incoming external calls. Become.

10 private branch exchange 30 storage device 31 control unit

Claims (7)

A private branch exchange connected to a plurality of extension telephones operating in a normal mode that allows incoming calls or an incoming call rejection mode that rejects incoming calls,
an all-calling unit for all-calling the plurality of extension phones in response to an incoming call;
a storage unit that stores incoming call acceptability information indicating whether each of the plurality of extension telephones operates in the incoming call rejection mode or the normal mode, and a predetermined threshold value;
When receiving a change permission request signal requesting permission to change from the normal mode to the call rejection mode, which is transmitted from each of the plurality of extension telephones, the call acceptance/rejection information stored in the storage unit counting the number of extension telephones operating in the normal mode among the plurality of extension telephones, and if the number of extension telephones is greater than the threshold, transmits a permission signal to the extension telephone that has transmitted the change permission request signal. At the same time, the content of the incoming call permission/prohibition information corresponding to the extension telephone of the transmission source is changed to the incoming call rejection mode, and if the number of telephones is equal to or less than the threshold value, the change permission request by the change permission request signal is rejected. and a general call manager for transmitting a refusal signal to the extension telephone of the transmission source. 2. The private branch exchange according to claim 1, wherein said predetermined threshold value represents a minimum number of incoming calls, among said plurality of extension telephones, to be maintained in said normal mode. When the number of calls is equal to or less than the threshold, the general call management unit prompts each of the plurality of extension phones operating in the call rejection mode to cancel the call rejection mode. 3. A private branch exchange according to claim 1, which transmits a request signal. The general call management unit assigns two levels of priority, high and low, to each of the plurality of extension telephones, and if the number of telephones is equal to or less than the threshold, the priority assigned to the extension telephone of the transmission source. and sending the rejection signal to the extension phone of the transmission source only when is low, and receiving the call only to the extension phone operating in the call rejection mode and having a low assigned priority among the plurality of extension phones. 4. The private branch exchange according to claim 3, which transmits a rejection cancellation request signal. A private branch exchange connected to first to n-th (n is an integer equal to or greater than 2) incoming groups each including a plurality of extension telephones operating in a normal mode capable of receiving an incoming call or an incoming call rejection mode for rejecting an incoming call, ,
an all-calling unit that makes all-out calls to the plurality of extension telephones included in one of the first to n-th groups in response to an incoming call;
incoming call acceptance/rejection information associated with each of said first to n-th groups and indicating in which of said incoming call rejection mode and said normal mode each of said plurality of extension telephones included in said group operates; and a storage unit in which a predetermined threshold value is stored;
stored in the storage unit when a change permission request signal requesting permission to change from the normal mode to the incoming call rejection mode is received from each of the plurality of extension telephones included in the one group; the number of extension telephones operating in the normal mode among the plurality of extension telephones is counted based on the reception acceptability information corresponding to the one group that is connected, and the number of extension telephones is greater than the threshold value corresponding to the one group. If there are many, it transmits a permission signal to the extension telephone that is the transmission source of the change permission request signal, changes the content of the incoming call permission/prohibition information corresponding to the extension telephone that is the transmission source to the incoming call rejection mode, is equal to or less than the threshold value, a general call management unit that transmits a refusal signal for refusing a change permission request by the change permission request signal to the extension telephone of the transmission source. . 6. The private branch exchange according to claim 5, wherein first to n-th outside line numbers are assigned to said first to n-th groups, respectively. It is connected to a plurality of extension telephones operating in a normal mode that allows incoming calls or a call rejection mode that rejects incoming calls, and each of the plurality of extension telephones operates in either the call rejection mode or the normal mode. A general call method by a private branch exchange including a storage unit that stores incoming call acceptability information indicating
When receiving a change permission request signal requesting permission to change from the normal mode to the call rejection mode, which is transmitted from each of the plurality of extension telephones, the call acceptance/rejection information stored in the storage unit a first step of counting the number of extension telephones operating in the normal mode among the plurality of extension telephones based on;
a second step of determining whether the number is greater than the threshold;
When it is determined that the number of telephones is greater than the threshold value, a permission signal is transmitted to the extension telephone that is the transmission source of the change permission request signal, and the content of the incoming call permission/prohibition information corresponding to the transmission source of the extension telephone is transmitted. a third step of changing to the call rejection mode;
a fourth step of transmitting a refusal signal for rejecting a change permission request based on the change permission request signal to the extension telephone as the transmission source when it is determined that the number of units is equal to or less than the threshold;
a fifth step of making a simultaneous call to the plurality of extension telephones in response to the incoming call;
A general call method by a private branch exchange, comprising:

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