JPH0595416A - Exchange system with DISA function - Google Patents

Abstract

PURPOSE:To constitute this system so that DISA can be made access again by a simple operation even in the case a called opposite party is busy or erroneous calling is executed and in the case a conversation to the called opposite party is finished, after DISA is made access. CONSTITUTION:When the external terminal of a telephone exchange executes plural procedures including the input operation of an extension telephone number of the telephone exchange, handling equivalent to the extension of the telephone exchange is executed to the external terminal. In the case the external terminal 8 receives an incoming call to the extension terminal 2 of the telephone exchange by using a DISA function, in the case the extension terminal 2 is busy or an erroneous number id dialed to the extension terminal 2, the information of a fact of busy or erroneous number dialing is returned to the external terminal 8, thereafter, from the external terminal 8, only the input operation of the extension telephone number is executed. In such a manner, an incoming call to desired extension terminals 2, 10 is executed.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention enables an external terminal of a telephone exchange to treat an external terminal as an extension of the telephone exchange by taking a plurality of procedures including an operation of inputting an extension telephone number of the telephone exchange. The present invention relates to a switching system with a DISA function.

[0002] Here, the DISA (Direct Inward System Access) function refers to an external caller of a telephone exchange as a trunk line as if it were an extension of the exchange system.
It provides a function of directly dialing a conference trunk, a station line trunk, etc. without an intermediary of a relay stand. Normally, when executing such a DISA function, an access number (usually an access number set so that the exchange automatically answers) is used. , Private public network station number or private network extension number) is assigned.

In the DISA function,
After the response, the sender is DTMF (PB; push button)
When a signal is used to dial a number (usually 3 or 4 digits) of a personal identification number (security code), the switching system confirms that the dialed number is valid, and then returns a dial tone of the switching system to the calling side. This allows the caller to dial (access) a device within the switching system. The above is the outline of the exchange system with the DISA function.

By the way, in recent years, as seen in connection between public line-dedicated line and connection between public line-dedicated line-public line, due to changes in the method of providing international leased line service, company-dedicated private line There is an increasing demand for connection between telephone networks that enable long-distance calls using lines. For the connection between the public line and the private line and the connection between the public line, the private line, and the public line, it is necessary to provide the above DISA function or a function similar thereto.

[0005]

2. Description of the Related Art FIG. 6 is a block diagram showing a switching system with a DISA function. The switching system with a DISA function is composed of a tone generating circuit 1, an extension telephone (extension terminal).
2, 10, a line circuit 3, 11, a switch circuit (communication path) 4, a control circuit 5, a station line track 6, a PB receiving circuit 7, an external telephone (external terminal) 8, and a storage device 9. .

Here, the tone generating circuit 1 generates various signals necessary for the switching connection operation, and the line circuits 3 and 1 are provided.
Reference numeral 1 is for transmitting a call signal from the corresponding extension telephones 2 and 10 and monitoring a communication path.

The switch circuit 4 is capable of exchanging connection between trunks and circuits, the control circuit 5 is for performing program control of exchange connection operation, and the station line trunk 6 is an interface circuit with the external telephone 8. Yes, the PB receiving circuit 7 receives and recognizes the DTMF signal, and the storage device 9 stores information necessary for program control.

[0008] With such a configuration, DIS via the station line
To make an incoming call A, follow the procedure shown in FIG.
First, the external telephone 8 is the DIS corresponding to the office trunk 6
Dial the A access number [see (1) in FIG. 4].

By registering the circuit corresponding to the access number in the exchange as a DISA circuit in the storage device 9 in advance in the form of a table as shown in FIG. 7, the control device 5 allows the DISA in the storage device 9 to be registered. It collates information and automatically responds to incoming calls to the circuit. On the transmitter side, which is mainly an exchange, the station line trunk 6 and the tone generation circuit 1
And the dial tone generated by the tone generation circuit 1 are transmitted to the external telephone 8. On the other hand, on the receiver side, the received signal from the external telephone 8 is connected to the PB (DTMF) receiving circuit 7 via the office line trunk 6 and monitored [see (2) in FIG. 4]. After listening to the dial tone, the external telephone 8 receives the personal identification number “XXXX” (for example, “123
4 ") with a DTMF tone [(3) in FIG. 4]
reference〕.

The control device 5 receives the dial signal via the PB (DTMF) receiving circuit 7 and collates the DISA information [password and received trunk line trunk position (or access number)] in the storage device 9. Then, it is judged whether the received signal is valid as a personal identification number, and if it is, the dial tone of the tone generating circuit 1 is connected to the transmitter side of the external telephone 8 via the office line trunk 6 and the external telephone 8 is connected. After sending, the receiving circuit 7 is connected to the receiver side through the office line trunk 6 and the dial information from the external telephone 8 is monitored [see (4) in FIG. 4]. In this state, the external telephone 8 can directly access the office line, the trunk line, and various service trunks as if it were the extension of the exchange.

If it is not correct, the busy or reorder tone of the tone generating circuit 1 is connected to the transmitter side of the external telephone 8 via the office line trunk 6 and sent to the external telephone 8 to disconnect the external telephone 8. Instruct. After listening to the dial tone, the external telephone 8 dials, for example, the extension number 5111 of the extension telephone 2 [see (5) in FIG. 4].

The control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7 and retrieves all the extension state information in the exchange in the storage device 9 and if the extension 5111 is busy or erroneous. When the number dialing is judged, the busy tone or the reorder tone of the tone generating circuit 1 is connected to the transmitter side of the external telephone 8 via the office line trunk 6 (see (6) in FIG. 4).

When a busy tone or a reorder tone is heard in this way, the receiver is placed on the external telephone 8 side (see (7) in FIG. 4). When making a call again, the same operation as above is performed.

As described above, in the conventional exchange system with the DISA function, the caller must recover when the other party is busy (listening to the caller busy tone) or dialing an incorrect number (calling the caller busy tone or reorder tone). No, he opened the link between the caller and the DISA line.

Further, by using the DISA function, a call can be made to a desired extension terminal and a call can be made, but the operation when the call is disconnected from the extension terminal side of the other party will be described with reference to FIG. Explain.

First, an incoming call [see (1) in FIG. 5], a dial tone [see (2) in FIG. 5], a secret code transmission [see (3) in FIG. 5], a dial tone [(4) in FIG. 5] reference〕,
The description of the procedure up to the sending of the partner number [see (5) in FIG. 5] will be made with reference to FIG. 4 described above ((1) to (5) in FIG. 4).
Description of].

After the sending of the other party's number (see (5) in FIG. 5), the control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7 and stores the dial information in the storage device 9 in the exchange. After searching all extension status information and determining that the extension 5111 is empty, the line circuit 3 causes the extension telephone 2 to
Send a call signal to. On the other hand, the ringback tone of the tone generating circuit 1 is sent to the external telephone 8 through the office line trunk 6 [see (6) in FIG. 5].

The control device 5 receives the response signal from the extension telephone 2 via the line circuit 3 and, after opening the tone generating circuit 1,
Cut-through is provided between the trunk line trunk 6 and the line circuit 3. As a result, the extension telephone 2 and the external telephone 8 are brought into a call state (see (7) in FIG. 5). The line circuit 3 stops the transmission of the calling signal in response to the extension telephone 2's response.

On the other hand, upon receipt of the disconnection signal from the extension telephone 2, the control device 5 releases the connection between the extension telephone 2 and the office line trunk 6, and the transmitter side of the external telephone 8 reorders the tone of the tone generating circuit 1. Are connected via the trunk line trunk 6 [see (8) in FIG. 5].

When the reorder tone is heard in this manner, the receiver is placed on the external telephone 8 side [see (9) in FIG. 5]. When making a call again, the same operation as above is performed.

As described above, in the conventional exchange system with the DISA function, the caller must recover when the other party is disconnected, and once the link between the DISA line with the caller is released, the DISA is accessed again. Caller and DI
The link between the SA lines was recaptured.

[0022]

However, in the conventional switching system with the DISA function as described above, if the dialed party is busy or erroneously dialed after the DISA is accessed, the DISA is accessed again,
The link between the caller and the DISA line has to be reacquired, which makes it difficult to acquire the access line during busy times, and when the public network is used, it is useless to dial again. There is a problem that it costs money.

Also, once the DI of the partner station is sent via the international leased line.
Even after the SA has been accessed and the conversation with the dialed party has ended, there is no function to continuously dial another party while keeping the leased line.
After opening the currently connected international line, it is necessary to capture the international line again and redial from DISA access.

In addition, for example, due to the time difference between Japan and the United States, calls using the international leased line are concentrated in a specific time zone, and it is often difficult to reacquire the international leased line. There is also a problem that it takes a long time.

The present invention was devised in view of such problems, and even after the DISA is accessed, even if the called party is busy or erroneously dialed, or even if the conversation with the called party ends, DIS with a simple operation
It is an object of the present invention to provide a switching system with a DISA function that makes A accessible.

[0026]

Therefore, the DI of the present invention
The exchange system with the SA function enables the external terminal of the telephone exchange to perform a plurality of procedures including the operation of inputting the extension telephone number of the telephone exchange to treat the external terminal as the same as the extension of the telephone exchange. In the function-equipped exchange system, when the external terminal receives the call to the extension terminal of the telephone exchange by using the DISA function, the extension terminal is busy or an incorrect number is dialed to the extension terminal. In this case, the information indicating busy or incorrect number dialing is returned to the external terminal, and thereafter, only the input operation of the extension telephone number is performed from the external terminal to execute the incoming call to the desired extension terminal. It is characterized in that (claim 1).

Further, in the exchange system with the DISA function of the present invention, when the extension terminal is busy when the external terminal receives the extension terminal of the telephone exchange using the DISA function, It is characterized in that information indicating that the user is busy is returned to the external terminal, and after the required time has elapsed, the incoming call to the extension terminal is automatically executed again (claim 2).

Further, in the exchange system with the DISA function of the present invention, after the external terminal uses the DISA function to cause the extension terminal of the telephone exchange to receive the call and to talk with the extension terminal, When the call is disconnected from the extension terminal side, information to that effect is returned to the external terminal, and then
The incoming call to the desired extension terminal is executed by only inputting the extension telephone number from the external terminal (claim 3).

[0029]

In the switching system with DISA function of the present invention described in claim 1, when the external terminal uses the DISA function to reach the extension terminal of the telephone exchange, the extension terminal is busy. Or an incorrect number dialing to the extension terminal, information indicating busy or incorrect number dialing is returned to the external terminal, and then only the extension telephone number is input from the external terminal. By
The incoming call to the desired extension terminal is executed.

Further, in the exchange system with a DISA function of the present invention according to claim 2, when the external terminal uses the DISA function to reach an extension terminal of the telephone exchange,
If the extension terminal is busy, information indicating that the extension terminal is busy is returned to the external terminal, and then, after a lapse of the required time,
The incoming call to the extension terminal is automatically executed again.

Furthermore, the DISA of the present invention according to claim 3
In the function-equipped exchange system, the external terminal uses the DISA function to cause an extension terminal of the telephone exchange to receive a call, to make a call with the extension terminal, and then to disconnect the call from the extension terminal side. In this case, the information to that effect is returned to the external terminal, and thereafter, only the input operation of the extension telephone number is performed from the external terminal to execute the incoming call to the desired extension terminal.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. Now, also in the embodiment of the present invention, the system configuration is as shown in FIG. 6 described above. That is,
The exchange system with the DISA function includes a tone generating circuit 1, extension telephones (extension terminals) 2, 10, line circuit 3,
11, switch circuit (communication path) 4, control circuit 5, line track 6, PB receiving circuit 7, external telephone (external terminal)
8 and a storage device 9.

First, the operation for making a DISA incoming call via a station line will be described with reference to FIG. First, the external telephone 8 dials the DISA access number corresponding to the office line trunk 6 [see (1) in FIG. 1].

By registering the circuit corresponding to the access number in the exchange as a DISA circuit in the storage device 9 in advance in the form of a table as shown in FIG. It collates information and automatically responds to incoming calls to the circuit. On the transmitter side, which is mainly an exchange, the trunk line trunk 6 and the tone generation circuit 1
And the dial tone generated by the tone generation circuit 1 are transmitted to the external telephone 8. On the other hand, on the receiver side, the received signal from the external telephone 8 is connected to the PB (DTMF) receiving circuit 7 via the office line trunk 6 and monitored [see (2) in FIG. 1]. After listening to the dial tone, the external telephone 8 receives the personal identification number “XXXX” (for example, “123
4 ") with a DTMF tone [(3) in FIG. 1]
reference〕.

The control device 5 receives this dial signal via the PB (DTMF) receiving circuit 7 and compares it with the DISA information [password and secret line trunk position (or access number)] in the storage device 9. Then, it is judged whether the received signal is valid as the personal identification number. If it is, the dial tone of the tone generating circuit 1 is connected to the transmitter side of the external telephone 8 via the trunk line 6 and the external telephone 8 is connected. Then, the receiving circuit 7 is connected to the receiver side via the office line trunk 6 and the dial information from the external telephone 8 is monitored. In this state, the external telephone 8 can directly access the office line, trunk line, and various service trunks as if it were an extension of this exchange [see (4) in FIG. 1].

If it is not correct, the busy or reorder tone of the tone generating circuit 1 (a voice announcement may be used) is connected to the transmitter side of the external telephone 8 via the office line trunk 6 and is sent to the external telephone 8. hand,
Instruct to disconnect the external telephone 8.

After listening to the dial tone, the external telephone 8 dials the extension number 5111 of the extension telephone 2 of the partner (see (5) in FIG. 1). The above procedure is the same as the conventional one [see (1) to (5) of FIG. 4].

Then, the control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7, retrieves all the extension state information in the exchange in the storage device 9, and if the extension 5111.
Is busy or is dialing an incorrect number,
Connect the busy tone or reorder tone of the tone generating circuit 1 (may be an announcement by voice) to the transmitter side of the external telephone 8 via the office line trunk 6, and then connect the receiving circuit 7 to the receiver side via the office line trunk 6. , The dial information from the external telephone 8 is monitored [see (6) in FIG. 1].

Thereafter, the external telephone 8 retains the access line to the office line trunk 6 and dials the next destination (for example, the extension telephone 10) while dialing the special number for redialing (pre-registered in the exchange). Dial example #) [see (7) in FIG. 1].

The control device 5 receives the dial information of the external telephone 8 through the receiving circuit 7 and recognizes that # is a special number for redialing DISA by collating it with the number information in the storage device 9. After the above recognition, the external telephone 8
Dial tone generated by the tone generation circuit 1 (may be an announcement by voice) is connected to the transmitter side of the external telephone 8 via the station line trunk 6 so that the receiver side can continue to receive the signal. 7 is connected via the office line trunk 6 and the dial information from the external telephone 8 is monitored [see (8) in FIG. 1].

The control device 5 is designed to monitor only the reception of the special number # while the external telephone 8 is connected to the busy tone and the reorder tone, and ignore the signals other than the signal.

After listening to the dial tone, the external telephone set 8 dials the extension number "5112" of the next extension telephone set 10 (see (9) in FIG. 1). The control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7, and after judging that the extension “5112” is available,
Connect the ringback tone in the tone generation circuit 1 to the transmitter side of the external telephone 8 via the office line trunk 6,
Line circuit 11 for the incoming telephone 10 (extension 5112)
Then, a calling signal is transmitted and the receiving circuit 7 is opened [see (10) in FIG. 1].

The control device 5 receives the response signal from the receiving telephone set 10 via the line circuit 11, opens the tone generating circuit 1, and then cuts off between the office line trunk 6 and the receiving telephone set 10. As a result, the incoming telephone 10 and the external telephone 8 are brought into a call state (see (11) in FIG. 1). The line circuit 11 stops the transmission of the calling signal in response to the incoming telephone 10 response. After that, by disconnecting the external telephone 8,
The connection between the called telephone 10 and the external telephone 8 is restored [see (12) in FIG. 1].

In this way, after the external telephone terminal 8 of the exchange having the DISA function accesses the DISA line,
Special number (special number) while listening to busy or reorder tones
Dialing allows the switch to recognize the special number and return a dial tone to the caller while still capturing the link between the caller and the DISA line. This allows the caller to access (dial) the device in the switching system.

In the above embodiment, the exchange is a special code #.
When a caller returns a dial tone after receiving the call, but the caller does not recover for the required time (fixed time), it automatically returns the tone and allows the caller to access the device in the switching system. , A similar effect is obtained.

Also, as in the above embodiment, the external telephone 8
When the extension telephone of the telephone exchange is called by using the DISA function and the extension telephone is busy or dials an incorrect number to the extension telephone, the external telephone 8 is busy or has an incorrect number. By returning the information indicating that it is a dial, and then performing the operation of inputting the extension telephone number from the external telephone 8 to execute the incoming call to the desired extension telephone, the external telephone uses the DISA function. If the extension telephone is busy, the information indicating that the extension telephone is busy is returned to the external telephone, and then, after the required time has elapsed, the extension telephone is automatically restarted. It is also possible to make an incoming call to.

That is, the operation in this case becomes a sequence chart as shown in FIG. First, (1) to FIG.
The procedure up to (6) is the same as the procedure up to (1) to (6) in FIG.

After the processing of (6) in FIG. 2, the external telephone 8 is a special number for redialing registered in advance in the exchange so that the external telephone 8 dials again while capturing the access line to the office line trunk 6. Dial (example # 1) [see (7) in FIG. 1]. As a result, the control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7,
Is collated with the number information in the storage device 9 to recognize that it is a special number for redial of DISA, and automatically receives the partner number "5111" again. The subsequent procedure [(8) to (10) in FIG. 3] is the same as the procedure from (10) to (12) in FIG.

If the special number is # 0, the service shown in the sequence chart of FIG. 1 (the service of inputting a telephone number from an external terminal) can be provided. That is, two kinds of services can be received by selecting a special number.

In the above embodiment, the exchange is a special code #.
Waiting for the reception of 1 and automatically dialing the other party's number again, but if the caller does not recover for the required time (fixed time),
The same effect can be obtained by automatically executing the dial. Even in this case, the same effects and advantages as those of the above-described embodiment can be obtained.

Next, using the above DISA function,
I was able to make a call to the desired extension terminal,
The operation when the call is disconnected from the extension terminal side of the other party will be described with reference to FIG.

First, an incoming call [see (1) in FIG. 3], a dial tone [see (2) in FIG. 3], a secret code transmission [see (3) in FIG. 3], a dial tone [(4) in FIG. 3] reference〕,
The procedure up to the sending of the partner number [see (5) in FIG. 3] will be described with reference to FIG. 1 described above ((1) to (5) in FIG. 1).
Description of].

After sending the partner number (see (5) in FIG. 3), the control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7 and stores it in the exchange in the storage device 9. After searching all the extension state information and determining that the extension "5111" is empty, the call signal is sent from the line circuit 3 to the extension telephone set 2. On the other hand, the ringback tone of the tone generating circuit 1 is sent to the external telephone 8 through the office line trunk 6 (see (6) in FIG. 3).

Further, the control unit 5 receives the response signal from the extension telephone set 2 via the line circuit 3, opens the tone generation circuit 1, and then cuts through between the office line trunk 6 and the line circuit 3. As a result, the extension telephone 2 and the external telephone 8 are brought into a call state (see (7) in FIG. 3). The line circuit 3
Stops the transmission of the calling signal in response to the extension telephone 2 response.

After that, when the control device 5 receives the disconnection signal of the extension telephone 2, the connection between the extension telephone 2 and the office line trunk 6 is released, and the dial tone of the tone generating circuit 1 is given to the transmitter side of the external telephone 8. Connect via the trunk line trunk 6 and connect the receiving circuit 7 to the receiver side
A connection is made via the network and the dial information from the external telephone 8 is monitored [see (8) in FIG. 3].

After the external telephone 8 listens to the dial tone, the extension telephone number "5" of the next extension telephone 10 of the other party is received.
When "112" is dialed (see (9) in FIG. 3), the control device 5 receives the dial information of the external telephone 8 via the receiving circuit 7 and retrieves all extension state information in the exchange in the storage device 9. After determining that the extension 5112 is empty,
A call signal is sent from the line circuit 11 to the extension telephone 10. On the other hand, the ringback tone of the tone generating circuit 1 is sent to the external telephone 8 through the office line trunk 6 (see (10) in FIG. 3).

Further, the control device 5 receives the response signal of the extension telephone set 10 via the line circuit 11, opens the tone generation circuit 1, and then cuts off between the office line trunk 6 and the line circuit 11. As a result, the extension telephone 10 and the external telephone 8 are brought into a call state (see (11) in FIG. 3). In addition,
The line circuit 11 stops the transmission of the calling signal in response to the response from the extension telephone 10.

After that, the control unit 5 receives the disconnection signal of the extension telephone 10 and releases the connection between the extension telephone 10 and the office line trunk 6, and the dial tone of the tone generating circuit 1 is sent to the telephone transmitter of the external telephone 8 to the office line. Connect via the trunk 6 and connect the receiving circuit 7 to the receiver side on the trunk line trunk 6
A connection is made via the Internet and the dial information from the external telephone 8 is monitored [see (11) in FIG. 3].

By receiving the restoration signal of the external telephone 8, the connection between the line circuit 11 and the external telephone 8 is restored [see (12) in FIG. 3]. If you hang up the call from the other party's extension phone and enter only the telephone number of the next party's extension phone, you can redial the service as many times as you like, instead of just once. You can also

In this way, the exchange having the DISA function detects the disconnection on the called side, and the caller and the DISA are automatically connected.
A dial tone can be returned to the caller while still capturing the link between the lines, which allows the caller to easily access (dial) a device within the switching system.

In each of the above-described embodiments, the DISA line incoming from the office line (public network) is described, but it is clear that the same effect can be obtained by the incoming from the trunk line (domestic / international leased line). Is. Similarly, although the called side is described as an extension belonging to the same switching system as the DISA line, it is clear that the same effect can be obtained even when a telephone in another switching system is dialed via a trunk line or an office line. ..

[0062]

As described above in detail, the DISA of the present invention
According to the function-equipped exchange system (Claim 1), when the external terminal receives a call to the extension terminal of the telephone exchange by using the DISA function, the extension terminal is busy or an incorrect number is dialed to the extension terminal. If it is, the information indicating busy or incorrect number dialing is returned to the external terminal, and then only the input operation of the extension telephone number is performed from the external terminal to execute the incoming call to the desired extension terminal. Therefore, there is an advantage that DISA can be accessed again by a simple operation.

In the exchange system with the DISA function of the present invention (claim 2), when the extension terminal is busy when an external terminal uses the DISA function to reach the extension terminal of the telephone exchange. , The information indicating that the terminal is busy is returned to the external terminal, and after the required time has elapsed, the incoming call to the extension terminal is automatically executed again.
Similar to the above case, there is an advantage that DISA can be accessed again by a simple operation.

Further, according to the exchange system with the DISA function of the present invention (claim 3), the external terminal uses the DISA function to cause the extension terminal of the telephone exchange to receive the call and make a call with the extension terminal. After that, when the call is disconnected from the extension terminal side, information to that effect is returned to the external terminal, and then only the input operation of the extension telephone number is performed from the external terminal to receive the call to the desired extension terminal. As described above, there is an advantage that DISA can be accessed again by a simple operation.

[Brief description of drawings]

FIG. 1 is a sequence chart illustrating an embodiment of the present invention.

FIG. 2 is a sequence chart illustrating an example of the present invention.

FIG. 3 is a sequence chart illustrating an example of the present invention.

FIG. 4 is a sequence chart illustrating a conventional example.

FIG. 5 is a sequence chart illustrating a conventional example.

FIG. 6 is a block diagram showing a switching system with a DISA function.

FIG. 7 is a diagram showing an example of DISA information.

[Explanation of symbols]

 1 tone generation circuit 2 extension telephone (extension terminal) 3 line circuit 4 switch circuit (communication path) 5 control circuit 6 station line track 7 PB receiving circuit 8 external telephone (external terminal) 9 storage device 10 extension telephone (extension terminal) 11 Line circuit

Claims (3)

[Claims] 1. A telephone exchange external terminal (8) treats the external terminal (8) as an extension of the telephone exchange by performing a plurality of procedures including an input operation of an extension telephone number of the telephone exchange. In a switching system with a DISA function capable of performing a call, when the external terminal (8) uses the DISA function to reach the extension terminal (2) of the telephone exchange, the extension terminal (2) is busy. In the case of an incorrect number dialing to the extension terminal (2), information indicating busy or incorrect number dialing is returned to the external terminal (8), and then from the external terminal (8). The desired extension terminal (2, 10) can be obtained by only inputting the extension telephone number.
A switching system with a DISA function, which is characterized by executing an incoming call to. 2. The telephone exchange external terminal (8) treats the external terminal (8) as an extension of the telephone exchange by performing a plurality of procedures including an input operation of an extension telephone number of the telephone exchange. In a switching system with a DISA function capable of performing a call, when the external terminal (8) uses the DISA function to reach the extension terminal (2) of the telephone exchange, the extension terminal (2) is busy. In the case where the call is received, information indicating that the user is busy is returned to the external terminal (8), and after that, after a required time has elapsed, the incoming call to the extension terminal (2) is automatically executed again. , DISA
Exchange system with functions. 3. The telephone exchange external terminal (8) treats the external terminal (8) as an extension of the telephone exchange by performing a plurality of procedures including an input operation of an extension telephone number of the telephone exchange. In the exchange system with a DISA function capable of performing the extension, the external terminal (8) uses the DISA function to cause the extension terminal (2) of the telephone exchange to receive the call, and the extension terminal (2)
When a call is disconnected from the extension terminal (2) after a call is made between the extension terminal (2) and the extension terminal (8), information indicating that is returned to the extension terminal (8), and then the extension from the extension terminal (8) An exchange system with a DISA function, characterized in that an incoming call to a desired extension terminal (10) is executed by only inputting a telephone number.