KR960001085B1 - Subscriber coupling device for a private exchanger - Google Patents

Abstract

confirming whether a line of an internal subscriber is busy or not; if the DIFA function is not performed, transferring a busy sound to the external subscriber; if the DIFA function is performed in the step, checking the performance of an automatic DIFA function; in case of the performance of the automatic DIFA function, checking which one is set, a group hunt DIFA, a camp DIFA, or a call wait DIFA; in case of the performance of the group hunt DIFA, making a phone call by connecting the internal subscriber to the external subscriber; in case of the performance of the call wait DIFA, making a phone call by connecting the external subscriber to the internal subscriber in turns; and in case that the automatic DIFA is not performed, transferring a DIFA announcement to the external subscriber, and checking the input of the DIFA function code.

Description

How to connect external subscribers when calling internal subscribers of private exchange

1 is a flowchart illustrating a method of connecting an external subscriber during extension subscriber communication of a conventional private exchange.

2 is a block diagram of a private exchange for applying the present invention.

3 is a flowchart illustrating a process of connecting an external subscriber during extension subscriber communication of a private exchange according to the present invention.

* Explanation of symbols for main parts of the drawings

10A: CO subscriber interface unit 10B: Extension subscriber interface unit

20A: trunk line controller 20B: station controller

30: central control unit 40: DTMF identification unit

50: DIFA control unit 60: switching unit

70: information broadcast transmission device 80: memory unit

80A: RAM 80B: ROM

According to the present invention, when an external subscriber is calling a subscriber in a direct inward dialing method of a private exchange (hereinafter referred to as DID), the subscriber is in a call in various ways. The present invention relates to an external subscriber connection method that enables an external subscriber to make a call with a corresponding subscriber or a neighboring subscriber even if the external subscriber repeatedly dials to call the corresponding subscriber or a neighboring subscriber.

In general, in the case of connecting the external subscriber to the subscriber in the conventional private exchange, it was connected in the order shown in FIG. First, when an external subscriber calls a private subscriber's extension subscriber by using a DID, a case where the subscriber is busy (B) and when the subscriber is busy (A) is also largely divided. At this time, when the subscriber is in a busy state, the call is made at the same time as the subscriber's call answering, but when the subscriber is busy, the external subscriber hears a busy tone and on-hook the handset to recover the call. In this case, when the external subscriber tries to make a call again, the user must dial again as shown in C until the extension subscriber is busy.

In the conventional method as described above, when the subscriber is in a call, the external subscriber needs to dial again to call the subscriber in order to talk to the subscriber, and the subscriber has to make an important call or emergency when the subscriber is busy. There is a problem that can not answer the phone.

The present invention has been made in order to solve the above problems, when the external subscriber is calling the extension subscriber, when the corresponding subscriber is busy, by connecting the external subscriber to the extension subscriber or the adjacent extension subscriber in the call It is an object of the present invention to provide a method of connecting an external subscriber during an extension subscriber call of a private exchange that enables a subscriber to call a corresponding subscriber or an adjacent subscriber even if the subscriber does not call the corresponding subscriber repeatedly by repeatedly dialing.

In order to achieve the above object, the method for connecting an external subscriber during a private subscriber call in the private exchange according to the present invention includes: a first process of checking whether the external subscriber is busy while the external subscriber makes a telephone call to the subscriber; In the first process, when the extension subscriber is not in a call, a ring tone is sent to the external subscriber and at the same time, a ring signal is sent to the extension subscriber, and when the extension subscriber answers, the call path is connected between the external subscriber and the subscriber. A second process of making a call; A third step of checking whether the DIFA function is performed when the extension subscriber is busy in the first step; A fourth step of recovering the call to a maintenance state when the external subscriber is on-hook after transmitting a ringing tone to the external subscriber when it is determined that the DIFA function is not performed in the third step; A fifth step of checking whether the automatic DIFA is performed when it is determined that the DIFA function is performed in the third step; A sixth step of checking whether the group hunt DIFA and the camp are set to automatically perform one of the DIFA and the call-weight DIFA when confirming that the automatic DIFA is performed in the fifth step; A seventh step of calling another extension subscriber in a non-call adjacent to the extension subscriber to make a call by connecting another adjacent subscriber and an external subscriber when the group hunt DIFA is automatically performed in the sixth step; An eighth step of allowing the extension subscriber to make a call by connecting the external subscriber to the extension subscriber when the extension is terminated by the extension when the camp-on DIFA is automatically performed in the sixth step; A ninth step of allowing the extension subscriber to make a call by alternately connecting an external subscriber who is in a call and an external subscriber who has made the call to the extension subscriber side when the callwait DIFA is set to automatically perform a call weight DIFA in the sixth step; If it is determined that the automatic DIFA is not performed in the fifth step, a DIFA guide broadcast for informing the procedure of using the DIFA function is sent to the external subscriber, and then a DIFA function code is input by receiving a digit authorized from the external subscriber. The tenth step of checking whether or not the service; An eleventh step of checking whether a group hunt DIFA function code, a camp-on DIFA function code, or a callweight DIFA function code is input when the DIFA function code is input in the tenth step; A 12th step of calling another extension subscriber in a non-call adjacent to the extension subscriber when the group hunt DIFA function code is input in step 11 to connect the other extension subscriber to an external subscriber; A step 13 of allowing the extension subscriber to make a call by connecting the external subscriber to an extension subscriber after the call-on DIFA function code is input in step 11; A fourteenth step of allowing the extension subscriber to make a call by connecting the external subscriber who is on the line with the external subscriber who has made the call to the extension subscriber side alternately when the call weight DIFA function code is input in step eleven; If the DIFA function code is not input in the tenth step, if the extension subscriber number is input, it comprises a fifteenth step of calling the extension subscriber corresponding to the extension subscriber number to connect to the external subscriber to make a call; .

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

Private exchange according to the present invention, as shown in Figure 2 subscriber line interface unit 10A, extension subscriber interface unit 10B, trunk line control unit 20A, extension control unit 20B, central control unit 30, DTMF The identification unit 40, the DIFA (Direct Inward Feature Access) control unit 50, the switching unit 60, the guide broadcast transmission device 70 and the memory unit 80 is provided. The guide broadcast transmission device 70 records and stores various guide broadcasts, and outputs the guide broadcasts to the trunk line side via the switching unit 60 and the trunk line subscriber interface unit 10A under the control of the central controller 30. The trunk line subscriber interface unit 10A performs a function of matching trunk lines. The trunk line subscriber interface unit 10A transmits a call voice applied from the trunk line to the switching unit 60 and performs a voice call and announcement broadcast from the switching unit 60. It transmits to the trunk line, and transmits the call signal and DTMF (Dual Tone Multi Frequency) signal from the trunk line to the trunk line control unit 20A, and the music, standby sound, speech sound, and the like applied from the trunk line control unit 20A. Deliver the ringing tone to the trunk line. The trunk line controller 20A detects a call signal applied from the trunk line subscriber interface unit 10A, outputs the corresponding sensing information to the central controller 30, and outputs a DTMF signal applied from the trunk line subscriber interface unit 10A. Detect and output the corresponding sensing information to the DTMF identification unit 40, and the DIFA control unit 50 generates a ringing tone and a ringing tone under the control of the central control unit 30, and outputs the ringing tone to the subscriber line interface unit 10A. , According to the control of the DIFA control unit 50 generates music and atmospheric sound and outputs it to the CO line subscriber interface unit 10A. The switching unit 60 forms a communication path between the trunk line subscriber interface unit 10A and the subscriber station interface unit 10B under the control of the central control unit 30 or the DIFA control unit 50. The extension subscriber interface unit 10B performs a function of matching the extension, and transmits the call voice applied from the switching unit 60 to the subscriber side and the call voice applied from the extension subscriber to the switching unit 60 side. Transmits a ring signal, a call wait tone, and a camp on tone applied from the extension controller 20B to the subscriber, and transmits a hook status signal applied from the subscriber. It transfers to the control part 20B side. The station controller 20B generates a ring signal under the control of the central controller 30 or the DIFA controller 50, and outputs the ring signal to the subscriber subscriber interface unit 10B. The call weight tone is controlled by the DIFA controller 50. And generates a camp on tone and outputs it to the subscriber interface unit 10B, and sends the hook status signal of the subscriber to the DIFA control unit 50 and the central controller 30 to be applied through the subscriber interface unit 10B. Output The central control unit 30 stores the automatic DIFA setting information applied through the terminal (not shown in the figure) in the RAM 82A of the memory unit 80 to automatically group hunt DIFA, camp on auto DIFA, or call weight auto. When the DIFA is set, information about whether each extension subscriber is busy or not is stored and managed in the RAM 80A of the memory unit 80, and a call signal for calling the extension subscriber from the trunk line controller 20A is applied. The DTMF identification unit 40 is operated to check the extension subscriber number authorized from the DTMF identification unit 40 to check whether the corresponding extension subscriber is in a call in the RAM 80A, and then the extension subscriber is not in a call. In this case, the station controller 20B is controlled to send a ring signal to the subscriber of the station by the station controller 20B to control the switching unit 60 when detecting the off-hook of the subscriber through the station controller 20B. Subscriber interface 10A and the subscriber interface unit 10B connect the call path, and if the corresponding subscriber is busy, the automatic DIFA operation is set in the RAM 80A of the memory unit 80 and the DIFA control unit Group hunt which outputs the DIFA operation instruction command corresponding to the (50) side and is applied through the DTMF identification unit 40 from the external subscriber if the automatic DIFA operation is not set in the RAM 80A of the memory unit 80. The function code and the camp output a DIFA operation instruction command to the DIFA control unit 50 to instruct to perform a corresponding DIFA operation according to the function code or the call weight function code. The DIFA control unit 50 has a software for performing a DIFA operation, and performs an DIFA operation according to a DIFA operation instruction command applied from the central control unit 30 to connect an external subscriber to an extension subscriber in a call. When performing the DIFA operation, the trunk line control unit 20 is controlled to generate music, a ringing sound, and a standby sound by the trunk line control unit 20A to output to the external subscriber side, and the station controller 20B is controlled by the station controller 20B. The ring signal, the call weight tone, and the camp on tone are generated and output to the subscriber side. The DTMF identification unit 40 operates under the control of the central control unit 30 or the DIFA control unit 50 to detect the DTMF signal applied from the trunk line control unit 20A, and detects the corresponding detection information by the central control unit 30 or the DIFA control unit. Output to (50) side. The memory unit 80 includes a RAM 80A having a ROM 80B, and the RAM 80A includes extension subscriber call state information for managing whether an extension subscriber authorized from the central controller 30 is busy. Saves the automatic DIFA flag to set whether to execute the automatic DIFA operation and the information about the automatic DIFA type to set whether to automatically perform group hunt DIFA, call weight DIFA, or camp-on DIFA. The ROM 80B stores a DIFA flag that sets whether to perform a DIFA operation.

The central control unit 30 outputs the corresponding DIFA operation instruction command to the DIFA control unit 50 according to the automatic DIFA set in the RAM 80A and the DIFA function code applied through the DTMF identification unit 40 from the external subscriber. The DIFA controller 50 performs a DIFA operation corresponding to the presentation of the central controller 30 when the DIFA operation instruction command is applied by the central controller 30. There are three kinds of automatic DIFA operations, group hunt DIFA, camp-on DIFA, and callweight DIFA, and these automatic DIFA operations are set in the RAM 80A of the memory unit 80. The central control unit 30 is connected to the RAM 80A when one of the group hunt DIFA, camp-on DIFA, and call-waiting DIFA is set as the automatic DIFA in the ram 80A when a call is made to an extension subscriber who is in a call from the outside. The DIFA control unit 50 automatically outputs a corresponding DIFA operation by outputting a DIFA operation instruction command for instructing execution of the corresponding DIFA operation.

On the other hand, the central control unit 30, if one of the group hunt DIFA, camp-on DIFA and call-waiting DIFA when the call to the subscriber in the call from the outside is not set to automatic DIFA in the RAM (80A), The DIFA control unit 50 issues a DIFA operation instruction command for instructing a subscriber to perform a corresponding DIFA operation according to a group hunt function code, a camp-on function code, or a call-waiting function code authorized through the DTMF identification unit 40. The output to the side causes the DIFA control unit 50 to perform the corresponding DIFA operation.

Among the three DIFA operations described above, the Group Hunt DIFA is a function that automatically connects other in-progress subscribers adjacent to the in-call extension subscriber when a call is made to an in-call subscriber. When a call is made to an extension subscriber who is in a call from an external subscriber, the extension subscriber who is on the line automatically connects the external subscriber to the corresponding subscriber after the call is terminated. When a call is received, the extension allows the subscriber to talk simultaneously with the external subscriber who has been calling and the newly dialed external subscriber.

The private exchange according to the present invention configured as described above operates in the order shown in FIG. 3 when connecting the external subscriber to the subscriber.

First, when the central control unit 30 receives a call signal from the trunk line via the trunk line subscriber interface 10A and the trunk line controller 20A and detects the call signal (step S101), the DTMF identification unit 40 is executed. It operates (step S102) and receives the digit by receiving the DTMF information applied from the trunk line via the DTMF identification unit 40 (step S103), and determines whether or not the received digit is the extension subscriber number. Is accessed by confirmation (step S104). When it is confirmed that the digit received in the step S104 is the extension number, the central control unit 30 stops the operation of the DTMF identification unit 40 (step S105), and accesses the RAM 80A to determine whether the corresponding subscriber is busy. Is checked (step S106). In this step S106, when the extension subscriber is not busy, the central control unit 30 controls the trunk line control unit 20A to generate a ring tone by the trunk line control unit 20A and passes through the trunk line subscriber interface unit 10A. At the same time as the ringing tone is transmitted to the station, the station controller 20B is controlled to generate a ring signal by the station controller 20B, and is sent to the station subscriber through the subscriber subscriber interface unit 10B (step S107). Check whether or not the extension subscriber responds by off-hook through step 20B (step S108). If the extension subscriber responds by off-hook, the switching unit 60 is controlled to establish a call path between the CO subscriber and the corresponding subscriber. The connection is made possible so that the call can be made (step S106).

In step S106, when the extension subscriber is busy, the central control unit 30 checks whether the DIFA function is performed by accessing the ROM 80B and checking whether the DIFA flag is set (step S109). If it is determined that the function is not performed, the CO line controller 20A is controlled to generate a ringing tone by the CO line controller 20A, which is sent to the subscribers of the CO line (step S10), and the corresponding CO line subscriber is turned on via the CO line controller 2A. It checks whether or not it hooks (step S111), and if the on-hook of the CO line subscriber is detected, the call is restored to an idle state (step S112).

If it is confirmed that the DIFA function is performed at step S109 at all times, the central controller 30 checks whether the automatic DIFA is performed by accessing the RAM 80A and checking whether the automatic DIFA flag is set (step S113). If it is confirmed that the automatic DIFA is performed, the process proceeds to step S170. If it is confirmed that the automatic DIFA is not performed, the process proceeds to step S129.

When it is confirmed in step S113 that the automatic DIFA is performed, the central control unit 30 accesses the RAM 80A to check whether any of the group hunt DIFA, camp-on DIFA, and callweight DIFA is set to automatic DIFA ( Step S170), the group hunt DIFA is set to automatic DIFA and proceeds to step S114 to perform the group hunt DIFA function. If the camp-on DIFA is set to automatic DIFA, the process proceeds to step S118 to perform the camp-on DIFA function. If the callweight DIFA is set to automatic DIFA, the flow proceeds to step S123 to perform the callweight DIFA function.

If the group hunt DIFA is set to automatic DIFA in the RAM 80A in step S170, the central control unit 30 outputs a command to the DIFA control unit 50 to instruct the group hunt DIFA to be performed (step S114). The non-calling extension number adjacent to the calling extension subscriber is checked from the RAM 80A (step S115), and if there is an adjacent non-calling extension number, the adjacent extension number is added to the DIFA controller 50 side. It outputs (step S116). At this time, the DIFA control unit 50 controls the trunk line control unit 20A to generate a call by the trunk line control unit 20A to send a ring tone to the trunk line subscriber and simultaneously control the station control unit 20B to the station control unit 20B. By generating a ring signal, the ring signal is sent to the adjacent subscribers (step S117). If the corresponding station extension responds by off-hook to the extension controller 20B (step S180), the switching unit 60 is controlled to connect the call path between the CO subscriber and the corresponding extension subscriber to make a call. (Step S181).

When the camp-on DIFA is set to the automatic DIFA in the RAM 80A in step S170, when the central control unit 30 outputs a command to the DIFA control unit 50 to perform the camp-on DIFA (step S118). In this case, the DIFA control unit 50 controls the station control unit 20B to generate a camp on tone by the station control unit 20B, and transmits a camp on tone to the subscribers in the call and simultaneously controls the trunk line control unit 20A. Air is generated by the CO line controller 20A and sent to the CO line subscriber (step S119). Thereafter, the DIFA control unit 50 checks whether the corresponding subscriber is on the hook through the extension controller 20B to terminate the call, and when the call of the corresponding subscriber is restored to an idle state (step S120), By controlling the trunk line control unit 20A to generate a ringing tone by the trunk line control unit 20A to transmit to the trunk line subscriber, and simultaneously control the station control unit 20B to generate a ring signal by the station control unit 20B to generate the ringing signal. (Step S121), and accordingly, when the extension subscriber is confirmed to be off-hook by the extension control unit 20B and responds (step S122), the switching unit 60 is controlled to communicate with the corresponding subscriber line and the subscriber. The call is then made to be connected (step S190).

When the call weight DIFA is set to the automatic DIFA in the RAM 80A in step S170, when the central control unit 30 outputs a command to the DIFA control unit 50 to perform the call weight DIFA (step S123). In this case, the DIFA control unit 50 controls the station control unit 20B to generate a call weight tone by the station control unit 20B, transmit the call weight tone to the subscribers in the call, and simultaneously control the trunk line control unit 20A to control the trunk line control unit 20A. Atmospheric noise is generated and sent to the CO line subscriber (step S124). Thereafter, the DIFA control unit 50 checks whether or not the corresponding subscriber has half-hooked the hook switch through the extension control unit 20B (step S125), and switches when the corresponding subscriber has half-hooked the hook switch. By controlling the unit 60, the CO line subscriber who is waiting for a call connects the extension subscriber to make a call, and at the same time, switches the CO line subscriber who is talking to the extension subscriber to the standby state (step S126). Then, the DIFA control unit 50 checks whether or not the corresponding subscriber has half-hooked the hook switch through the extension control unit 20B (step S127). By controlling the unit 60, the trunk line subscriber who is waiting for a call and the corresponding station subscriber are connected to make a call, and at the same time, the trunk line subscriber who has been talking with the corresponding station subscriber is put into the standby state (step S128), and the flow returns to the step S125. Perform repeat operation. On the other hand, in step S125, the DIFA control unit 50 continues the operation of step S124 if the extension subscriber does not half-on the hook switch, and if the extension subscriber does not half-on the hook switch in step S127, Continue the action.

When the central control unit 30 confirms that the automatic DIFA function is not performed in step S113, the DTMF identification unit 40 is controlled to operate the DTMF identification unit 40 (step S129), and guide broadcast transmission. The apparatus 70 is controlled to transmit the DIFA announcement to the subscriber line via the switching unit 60 and the subscriber line interface unit 10A (switching S130). At this time, for example, the contents of the DIFA announcement broadcasted from the announcement broadcast transmission device 70, "Hello? This is the Venus Information & Communication DIFA Service. The subscriber you are dialing is busy, dial another extension number or press '*' to call an adjacent subscriber and press '0' or press '*' to wait and call '1'. Press '*' and then press '2'. If you send the announcement to the subscribers, the subscribers can select the desired function by operating the keypad of the switcher according to the guidance. Thereafter, the central control unit 30 receives the digit by receiving the DIFA signal applied from the trunk line subscriber by the DTMF identification unit 40 (step S131). In this case, the keypad for informing the DIFA function code input from the trunk line subscriber. Check whether the '*' key is input (step S132), and if it is not the '*' key, check whether or not the digits authorized from the CO line subscriber are recorded in the RAM 80A. It is checked whether or not the digit is the subscriber number (step S134).

In step S134, if it is determined that the digit received from the CO line subscriber is the extension subscriber number, the central controller 30 controls the DTMF identification unit 40 to stop the operation of the DTMF identification unit 40 (step S135). Accesses the RAM 80A, checks whether the extension subscriber of the corresponding subscriber number is busy (step S136), and if the extension subscriber is not busy, controls the trunk line controller 20A to control the trunk line controller 20A. By generating a ring tone and transmitting it to the trunk line subscriber side, and simultaneously controlling the station control unit 20B, a ring signal is generated by the station control unit 20B and sent to the station subscriber side (step S137). 20B) checks whether or not the corresponding extension subscriber responds by off-hook (step S138). If the extension subscriber answers, the switching unit 60 is controlled to connect the call path between the CO subscriber and the corresponding subscriber. It makes a call (step S200).

If the DIFA function code is input from the CO line subscriber after the '*' key is input from the CO line subscriber in step S132 (step S133), the central control unit 30 checks which DIFA function selection code is input. If the digit ″ 0 ″ corresponding to the group hunt DIFA function code is input (step S139), the operation proceeds to step S114 to perform the group hunt DIFA function described above, and the camp-on DIFA function code is executed. When the corresponding digit 1 is input (step S140), the operation proceeds to step S118 to perform the above-described camp on DIFA function, and when the digit 2 corresponding to the call weight DIFA function code is input. In step S141, the operation proceeds to step S123 to perform the above-described call weight DIFA function.

As described above, the present invention connects an external subscriber to an extension subscriber or an adjacent extension subscriber when the external subscriber is calling while the external subscriber is calling the extension subscriber, so the external subscriber repeatedly dials the extension subscriber. Even if the call is not made, the subscriber or the subscriber can call the subscriber. Therefore, when the extension subscriber is busy, the external subscriber solves the problem of calling the extension subscriber again, and when the extension subscriber is busy, he / she does not receive an important call or an emergency call.

Claims (4)

A method for connecting an external subscriber during an extension subscriber call in a private exchange, comprising: a first step of checking whether the extension subscriber is busy when the external subscriber calls the extension subscriber; In the first process, when the extension subscriber is not in a call, a ring tone is sent to the external subscriber and at the same time, a ring signal is sent to the extension subscriber, and when the extension subscriber answers, the call path is connected between the external subscriber and the subscriber. A second process of making a call; A third step of checking whether the DIFA function is performed when the extension subscriber is busy in the first step; A fourth step of recovering the call to a maintenance state when the external subscriber is on-hook after transmitting a ringing tone to the external subscriber when it is determined that the DIFA function is not performed in the third step; A fifth step of checking whether the automatic DIFA is performed when it is determined that the DIFA function is performed in the third step; A sixth step of checking whether the group hunt DIFA, the camp-on DIFA, and the callweight DIFA are set to perform an automatic DIFA when the automatic DIFA is performed in the fifth step; A seventh step of calling another extension subscriber in a non-call adjacent to the extension subscriber to make a call by connecting another adjacent subscriber and an external subscriber when the group hunt DIFA is automatically performed in the sixth step; An eighth step of allowing the extension subscriber to make a call by connecting the external subscriber to the extension subscriber when the extension is terminated by the extension when the camp-on DIFA is automatically performed in the sixth step; A ninth step of allowing the extension subscriber to make a call by alternately connecting an external subscriber who is in a call and an external subscriber who has made the call to the extension subscriber side when the callwait DIFA is set to automatically perform a call weight DIFA in the sixth step; If it is determined that the automatic DIFA is not performed in the fifth step, a DIFA guide broadcast for informing the procedure of using the DIFA function is sent to the external subscriber, and then a DIFA function code is input by receiving a digit authorized from the external subscriber. The tenth step of checking whether or not the service; An eleventh step of checking whether a group hunt DIFA function code, a camp-on DIFA function code, or a callweight DIFA function code is input when the DIFA function code is input in the tenth step; A 12th step of calling another extension subscriber in a non-call adjacent to the extension subscriber when the group hunt DIFA function code is input in step 11 to connect the other extension subscriber to an external subscriber; A step 13 of allowing the extension subscriber to make a call by connecting the external subscriber to an extension subscriber after the call-on DIFA function code is input in step 11; A fourteenth step of allowing the extension subscriber to make a call by connecting the external subscriber who is on the call with the external subscriber who has made the call to the extension subscriber side alternately; If the DIFA function code is not input in the tenth step, if the extension subscriber number is input, the fifteenth step of calling the extension subscriber corresponding to the extension subscriber number to connect to the external subscriber to make a call; How to connect external subscribers to private subscribers in private exchanges. The method of claim 1, wherein the seventh and twelfth steps include: a first step of checking whether there is another non-calling subscriber who is adjacent to the extension subscriber in a call; A second step of transmitting a ringing sound to the external subscriber and transmitting a ringing signal to the adjacent subscriber, when it is determined in the first step that there is another non-calling subscriber who is adjacent to the extension subscriber in a call; A third step of checking whether another adjacent extension subscriber responds by off-hook after the second step; A fourth step of making a call by connecting a call path between the external subscriber and the other extension subscribers when the other extension subscribers respond in the third step; The fifth step of restoring the call to a dormant state when the external subscriber is on-hook after transmitting a ringing tone to the external subscriber when it is determined that there is no non-calling subscriber who is adjacent to the extension subscriber in the first step. Method of connecting an external subscriber during the extension subscriber call of the private exchange comprising a step. The method of claim 1, wherein the eighth and thirteenth steps include: a first step of transmitting a camp-on tone to the extension subscriber in a call and simultaneously transmitting music to the external subscriber; A second step of calling the external subscriber side and transmitting a ring signal to the internal subscriber side when the busy subscriber ends the call after the first step; And a third step of connecting the call path between the extension subscriber and the external subscriber when the extension subscriber responds by off-hook after the second step. . The method of claim 1, wherein the ninth process and the 14th process include: a first step of transmitting a call weight tone to the internal subscriber side in a call and at the same time transmitting an atmospheric sound to the external subscriber side; A second step of checking whether the extension subscriber half-on a hook switch after the first step; In the second step, when it is confirmed that the extension subscribers half-on the hook switch, a third step of connecting the external subscriber who is on hold to the subscriber to make a call and at the same time converting the external subscriber who is on the call to a call waiting state; Wow ; A fourth step of checking whether or not to turn on the subscriber hook switch after the third step; If it is confirmed in step 4 that the extension subscriber half-on the hook switch, the external subscriber who is waiting for a call is connected to the extension subscriber to make a call, and the external subscriber who is on the phone is switched to the call waiting state after the extension. A fifth step returning to the second step; A sixth step of returning to the first step and performing a repeating operation when it is confirmed in the second step that the extension subscriber does not half-on the hook switch; If it is confirmed in the fourth step that the subscriber extension does not half-on the hook switch, the subscriber returns to the third step and includes a seventh step of performing a repeating operation. How to connect.