JPH0451641A - High load test system - Google Patents

Abstract

PURPOSE:To easily conduct the high load test of an exchange for service synthesis digital communication network(ISDN) by originating a test call to a first primary group interface subscriber line from a basic interface subscriber line in a state where a return call means is connected to first and second primary group interface subscriber lines. CONSTITUTION:The return call means 100 is connected to the ISDN exchange 1 by the first primary group interface subscriber line 3-1 and the second primary group interface subscriber line 3-2 and the call is transmitted from the ISDN exchange 1 to the first primary group interface subscriber line 3-1. When a call setting message to which the telephone number DN31 of the incoming subscriber line 3-1 is added is received, the call setting message where the telephone number DN31 added to the call setting message is set to be an incoming telephone number is edited and it is transmitted from the second primary group interface subscriber line 3-2 to the ISDN exchange 1. Thus, the high load test of the ISDN exchange can be conducted without preparing a large scale device.

Description

[Detailed Description of the Invention] [Summary] Concerning a high-load test method for switching equipment for integrated services digital networks (ISDN), it is possible to test it without preparing large-scale equipment or expending much effort. The purpose is to apply a high load to the ISDN exchange, and it accommodates the basic interface subscriber line and the primary group interface subscriber line. In an ISDN exchange equipped with a function to add numbers, IS
Edit a call setup message that uses the telephone number added to the call setup message sent from the DN exchange to the first primary group interface subscriber line as the incoming telephone number, and send the call setup message to the first primary group interface subscriber line. When the call return means, such as a communication line or private branch exchange, returns the call from the second primary group interface subscriber line corresponding to the second primary group interface subscriber line to the ISDN exchange, and the first primary group interface subscriber line is fully busy. Enter the telephone number of the subscriber line to which you want to forward incoming calls.
a plurality of consecutive subscriber selection means held corresponding to the telephone number of the next group interface subscriber line, and a call is made from the basic interface subscriber line for testing to the first primary group interface subscriber line. By doing so, until the first primary interface subscriber line is all busy, the call is transferred from the second primary interface subscriber line to the first primary interface subscriber line via the call return means. After making a call to the subscriber line, the plural subscriber consecutive selection means attempts to receive the call on the subscriber line specified by the telephone number held corresponding to the telephone number of the first primary group interface subscriber line. Configure.

[Industrial Application Field] The present invention is applicable to integrated service digital communication networks (hereinafter referred to as ISD).
This invention relates to a high-load test method for switching equipment (referred to as N).

Two sets of information channels (hereinafter referred to as B channels) serve as interfaces for accommodating subscriber lines to ISDN exchanges.
and - sets of signal channels (hereinafter referred to as D channels), and, for example, thirty sets of B signal channels.
A primary group interface formed from a set of D-channels and a set of D-channels is recommended by the CCITT.

When testing this type of ISDN switch, it becomes necessary to apply a high load.

[Prior Art] FIG. 7 is a diagram showing an example of a conventional high load test method, and FIG. 8 is a diagram showing an example of another conventional high load test method.

In FIGS. 7 and 8, in the ISDN exchange 1, a basic interface subscriber line 2 as described above is accommodated in a network (NW) 11, and a primary group interface subscriber line 3 as described above is accommodated. It is accommodated in the network (NW) 11 via a digital terminal (DT) 12.

In FIG. 7, when applying a high load to the ISDN exchange 1, a private branch exchange (PBX) 4 is connected via the primary group interface subscriber line 3, and a large number of testers ) A call is made all at once to the ISDN exchange 1 from a large number of extensions 5 accommodated in the ISDN exchange 1 via the primary group interface subscriber line 3, and the basic interface subscriber line 2 accommodated in the ISDN exchange 1 or the ISDN The call is received by an automatic answering device (AT) 15 connected to the network (NW) 11 of the exchange 1.

In addition, in FIG. 8, when applying a high load to the ISDN exchange 1, a pseudo call generator (PCG) 6 is connected via the primary group interface subscriber line 3, and the pseudo call generator (PCG) ) 6 via the primary group interface subscriber line 3 to the basic interface subscriber line 2 or automatic answering device (AT) 15.

[Problem to be solved by the invention]

As is clear from the above explanation, in the conventional high load test method illustrated in FIG.
In order to apply a high load to the N exchange 1, a private branch exchange (PBX) 4 accommodating a large number of extensions 5 is connected via the primary group interface subscriber line 3, and a large number of testers It is necessary to make calls all at once from a large number of extensions 5 accommodated in
4), and required a large number of testers to spend a great deal of effort.

Furthermore, in the conventional high-load test method illustrated in FIG. It is necessary to prepare a call generator (PCG) 6), and the pseudo calls generated by the pseudo call generator (PCG) 6 are less random than artificial test calls, making it difficult to test according to actual conditions. There was a problem that it could not be executed.

An object of the present invention is to make it possible to apply a high load to an ISDN exchange to be tested without preparing a large-scale device and without expending much effort.

(Means for solving problems) FIG. 1 is a diagram showing the principle of the present invention.

In FIG. 1, 1 is an ISDN switch which is the object of the present invention, 2-1.2-2 and 3-1.3-2 are respective I
The basic interface subscriber line and the primary group interface subscriber line, DN, and DN2□ accommodated in the SDN exchange l are each the primary group interface subscriber line 3.
-1 and the telephone number assigned to the basic interface subscriber line 2-2.

Reference numeral 100 denotes call return means provided in the ISDN exchange 1 according to the present invention.

Reference numeral 200 denotes a plurality of subscriber consecutive selection means provided in the ISDN exchange 1 according to the present invention.

[Effect]

The ISDN exchange 1 has a function of adding the telephone number DN, □ of the terminating subscriber line 3-1 to the call setting message transmitted to the terminating subscriber line 3-1 when a call is received.

The call return means 100 is configured to send a call back from the ISDN exchange 1 to the first one.
Edit the call setting message that uses the telephone number DN31 added to the call setting message sent to the next group interface subscriber line 3-1 as the incoming telephone number, and send the call setting message to the first primary group interface subscriber line 3-1. is transmitted to the ISDN exchange 1 from the second primary group interface subscriber line 3-2 corresponding to .

When the first primary group interface subscriber line 3-1 is all busy, the multiple subscriber consecutive selection means 200 selects the telephone number DN2□ of the subscriber line to which the incoming call is transferred as the first primary group interface subscriber line 3-1. It is held in correspondence with the telephone number DN of the group interface subscriber line 3-1.

After that, the ISDN exchange 1 makes a call from the test basic interface subscriber line 2-1 to the first primary group interface subscriber line 3-1.
Until the next group interface subscriber line 3-1 is all busy,
After a call is made from the second primary group interface subscriber line 32 to the first primary group interface subscriber line 3-1 via the return calling means 100, the plural subscriber consecutive selection means 200 First primary group interface subscriber line 3-1
Telephone number D held corresponding to telephone number DNff,
An attempt is made to terminate the call on the subscriber line specified by N2°.

The TSDN exchange 1 has a first primary group interface subscriber line 3-1 and a second primary group interface subscriber line 3 corresponding to the first primary group interface subscriber line 3-1. It is considered that a plurality of sets of -2 and callback means 100 are provided.

Further, it is considered that the callback means 100 is a communication line that connects the first primary group interface subscriber line 3-1 and the second primary group interface subscriber line 3-2, Further, the call return originating means 100 is connected to the ISDN exchange 1 by a first primary group interface subscriber line 3-1 and a second primary group interface subscriber line 32,
When receiving a call setup message with the telephone number DN 31 of the terminating subscriber line 3-1 transmitted from the rSDN exchange 1 to the first primary group interface subscriber line 3-1, the received call Edit the call setup message with the telephone number DN31 added to the setup message as the incoming telephone number, and call a predetermined second call other than the first primary group interface subscriber line 3-1 accommodated in the ISDN exchange l. Primary group interface subscriber line 3-2 to ISDN switch 1
It is considered that the private branch exchange transmits to

Therefore, by simply making a test call from the basic interface subscriber line to the first primary interface subscriber line with the return call originating means connected to the first and second primary interface subscriber lines, Test calls corresponding to the number of B channels forming the first primary group interface subscriber line are rs
Since the signal is applied to the DN exchange, there is no need to prepare large-scale equipment such as a private branch exchange or a pseudo call generator.
Furthermore, there is no need for a large number of testers to spend a great deal of effort, and it becomes possible to easily perform high-load tests on the ISDN exchange.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a high load test method according to an embodiment of the present invention (claims 1 and 3), and FIG. 3 is a diagram showing an example of the high load setting process in FIG. FIG. 4 is a diagram showing a high load test method according to an embodiment of the present invention (claims 2 and 3), and FIG. 5 is a diagram showing a high load test method according to an embodiment of the present invention (claims 1 and 4). 6 is a diagram showing a high load test method, and FIG. 6 is a diagram showing an example of the high load setting process in FIG. 5. Note that the same reference numerals indicate the same objects throughout the figures.

In FIG. 2, the return calling means 100 in FIG.
As a result, a loopback path 7 is provided to loop back and connect the set of primary group interface subscriber lines 3-1 and 3-2, and the multiple subscriber consecutive selection means 20 in FIG.
0, a set of multi-line selection tables (MHG) 141 is provided in the main memory (MM) 14, and a fourth
In the figure, the loopback path 7 and multiline selection table (MHG) 141 in FIG. Furthermore, in FIG. 5, a private branch exchange 8 is provided as the return call means 100 in FIG. 1, and a plurality of consecutive subscriber selection means in FIG. Multi-line selection table (MHG) as 200
) 141 is provided.

In FIG. 2, the primary group interface subscriber line 3-
Thirty sets of B channels and one set of D channels formed on the primary group interface subscriber line 3
It is looped back and connected via a loopback path 7 to the corresponding thirty sets of B channels and one set of D channels formed on -2.

In FIGS. 2 and 3, the telephone number DN! assigned to the primary group interface subscriber line 31 is used by the tester to make a test call. A call setup message 5ETUP (DN, I) with , as the incoming telephone number is organized, and ISDN is sent via the D channel on the basic interface subscriber line 2-1.
When transmitted to the exchange 1, the ISDN exchange 1 returns a call establishment acceptance message CALLPROC to the D channel on the basic interface subscriber line 2-1, and the central controller (CC) 13 sends a call establishment message S E as is known. When T U P (D N 31 ) is received and analyzed and an empty B channel formed on the primary group interface subscriber line 1-1 is identified, the B channel and the called telephone number D N ! A call setup message S ET U P (D N 31 ) specifying + is compiled and sent to the D channel on the primary group interface subscriber 13-1.

Call setup message sent 5ETUP (DN3,)
is sent back to ISDN switch l via loopback path 7 and the D channel on primary group interface subscriber line 3-2.

ISDN switch 1 is a primary group interface subscriber line 3
-2, receives and analyzes the call setup message SETUP (D Nff+), and transfers the message from the primary group interface subscriber line 3-2 to the primary group interface subscriber line 3-2. When it is identified that a new call setup request has been made to the primary group interface subscriber line 3-2, the call setup acceptance message CALLPROC is returned to the D channel on the primary group interface subscriber line 3-2, and the After identifying the free B channel on line 3-1,
The same call setup message as above
D N31) and transmits it to the D channel on the primary group interface subscriber line 3-1.

The call setup acceptance message CALLPROC sent to the D channel on the primary group interface subscriber line 3-2 is:
ISDN switch l via the loopback path 7 and the D channel on the primary group interface subscriber line 3-1.
and also to the primary group interface subscriber line 3-1.
Call setup message 5ETU sent to D channel above
P (DN31) is sent back to the ISDN exchange 1 via the loopback path 7 and the D channel on the primary group interface subscriber line 3-2, as described above, and
Furthermore, it is added to the ISDN exchange 1 as a new call setup request.

Thereafter, in the same manner, after the ISDN exchange 1 transmits the thirtieth call setup message 5ETUP (DN31) to the D channel on the primary group interface subscriber line 3-1,
Call setup message sent back via D channel on next group interface subscriber f132
(D N31), there is no longer an empty B channel on the primary group interface subscriber line 3-1, and no call setup is possible for the primary group interface subscriber line 3-1. It becomes possible.

In such a case, the central controller f (CC) 13 refers to the multi-line selection table (MHG) 141 provided in the main memory (MM) 14 and sends the call setting message SET.
Telephone number DN specified in U P (DN3□),
, when identifying that the telephone number DN, □ is held as the forwarding destination telephone number, the telephone number DN,
Call setup message 5ETUP with □ as the incoming phone number
(DN22) and executes call setting processing for the basic interface subscriber line 2-2 to which the telephone number DN and □ have been assigned.

As a result of execution, if the call setup for the basic interface subscriber line 2-2 is successful, the ISDN exchange 1 sends a call setup message 5ETUP (DN22) to the D channel on the basic interface subscriber line 2-2.

A paging message ALERT indicating that a call is in progress is sent from the basic interface subscriber line 2-2 that received the call setup message 5ETUP CDN2□) to the ISDN exchange 1 via the D channel on the basic interface subscriber line 2-2.
ISDN exchange 1 returns the alert message ALERT to the D channel on primary group interface subscriber line 3-2 according to known procedures.

The paging message ALERT is returned to the ISDN exchange 1 via the loopback path 7 and the D channel on the primary group interface subscriber line 3-1, and in the same manner, the ISDN exchange 1 connects the primary group interface subscriber line 3-1. Alert message ALERT to D channel on subscriber line 3-2
D on the primary group interface subscriber line 3-1.
The process of receiving the paging message ALERT from the channel is repeated, and finally the D on the primary group interface subscriber line 31 is received.
The paging message ALERT received from the channel is returned via the D channel on the basic interface subscriber line 2-1.

As is clear from the above description, according to this embodiment, after connecting the primary group interface subscriber lines 3-1 and 3-2 through the loopback path 7, Group interface subscriber 1i1A
By simply making a test call with telephone number DN:++ of 3-1 as the incoming telephone number, the ISDN exchange 1 will have 30 more primary group interface subscribers! A test call arriving from 3-2 to the primary group interface subscriber line 3-1 is added.

Next, in FIG. 4, a set of primary group interface subscriber lines 311 to 3-1 accommodated in the ISDN exchange 1 is shown.
k connects to the corresponding primary group interface subscriber line 3-21 via loopback paths 7-1 to 7-k, respectively.
The main memory (MM) 14 includes a multi-line selection table (MHG) provided corresponding to each of the primary group interface subscriber lines 311 to 3-1k. 141-1 to 141-k, primary group interface subscriber lines 3-11 to 3-1k, respectively.
Telephone number DN, assigned to.

A plurality of basic interface subscriber lines 221 to 2-2 accommodated in the ISDN exchange 1 correspond to DN31□ to DN31□.
The telephone numbers DN2□ to DN, □ assigned to 2j are retained, and the same (phone numbers DN:III to DN from i basic interface subscriber lines 2-11 to 2-11 accommodated in the rsDN exchange l) , □, as the incoming telephone number, it is possible to double the number of test calls similar to those in FIG. 2.

Next, in FIG. 5, the primary group interface subscriber lines 3-1 and 3-2 accommodated in the ISDN exchange l are as follows:
Both are connected to a private branch exchange 8.

The private branch exchange 8 has a primary group interface subscriber line 3-1.
The thirty sets of B channels and one set of D channels formed above are connected to the primary group interface subscriber line 3-.
A loopback section (LB) corresponding to thirty corresponding sets of B channels and one set of D channels formed on 2.
831 is provided within the central control unit (CC) 83.

In FIGS. 5 and 6, in order for the tester to make a test call, a call setting message S E T U P is sent with the telephone number DN31 assigned to the primary group interface subscriber line 3-1 as the incoming telephone number. (D N 31 ) and sends it to the ISDN exchange 1 via the D channel on the basic interface subscriber line 2-1.
Call setup acceptance message CALLPR to D channel on 1
At the same time as returning the OC, the central control unit (CC) 13 sends a call setup message SETUP (DN a
1) is received and analyzed, and the primary group interface subscriber M
After identifying an empty B channel formed on S-1, a call setup message S E T U P (D N3
+) and transmits it to the D channel on the primary group interface subscriber line 3-1.

In the private branch exchange 8, the central controller (CC) 83 receives the call setup message SE T U P (D
N 31 ), a call setup message S E
The paging message ALERT for T U P (D N 3□) is returned to the ISDN exchange 1 via the D channel on the primary group interface subscriber line 3-1, and the loopback unit (LB) 831 is activated. do.

The activated loopback unit (LB) 831 receives the received call setup message S E T U P (D N 31
) Call setup message 5ET specifying the B channel on the primary group ink face subscriber line 3-2 corresponding to the B channel specified in ) and the terminating telephone number D N 3 +'
Edit the UP (DNz) and send it back to the SDN exchange 1 via the D channel on the primary group interface subscriber line 3-2.

The ISDN exchange 1 has a primary group interface subscriber line 3.
-1, the paging message ALERT sent back via the D channel on basic interface subscriber wA2-1
The call setup message 5ETUP (DN31) is sent back to the upper D channel, and subsequently received and analyzed from the D channel on the primary group interface subscriber line 3-2. 2, and identifies that a new request has been made for call setup from the primary group interface subscriber line 3-2 to the primary group interface subscriber line 3-1. After identifying a vacant B channel on the primary group interface subscriber line 3-1, a call setup message SET U P (D N3+) similar to that described above is created, and a Send to D channel.

The private branch exchange 8 receives the call setup message 5ETUP (DN31) sent to the D channel on the subscriber line 3-1.
When receiving the alert message, the alert message ALERT is sent in the same way as above.
is returned to the ISDN exchange 1 via the D channel on the primary group interface subscriber line 3-1.

The ISDN exchange 1 has a primary group interface subscriber line 3.
-2 to the primary group interface subscriber line 3-2.
The data is sent back to the private branch exchange 8 via the upper D channel.

On the other hand, the central control unit 1 (CC) 83 in the private branch exchange 8,
Call setup message 5ETU P (D N
s+), the loopback unit (LB) 831 is activated, and the activated loopback unit (LB) 831 is
As before, the received call setup message 5ETUP
Specify the B channel on the primary group interface subscriber line 3-2 corresponding to the B channel specified in (DN31), and edit the call setup message 5ETUP (DN, l) with telephone number DN31 as the incoming telephone number. IS via the D channel on the primary group interface subscriber line 3-2.
By sending the call back to the DN exchange @1, a new call setup request is added to the ISDN exchange 1.

Thereafter, in the same manner, the ISDN exchange 1 sends the 30th call setup message SETUP (DN3+) to the D channel on the primary group interface subscriber line 3-1.
The call setup message S is sent back via the D channel on the primary group interface subscriber line 32 after sending the call setup message S.
When E T U P (D NffI ) is received, there is no longer an empty B channel on the primary group interface subscriber line 3-1, and there is no free B channel on the primary group interface subscriber line 3-1. However, the central controller (CC) 13 uses the main memory (MM) as described above.
Multi-line selection table (MHC;
) 141, call setup message S E T U
Telephone number DN specified in P (DN 31),
, when it is identified that the telephone number DN0 is held as the forwarding destination telephone number, the telephone number DN0 is
Call setup message with z□ as the incoming phone number S E T
Edit U P (D N22) and enter the phone number D N
Basic interface subscriber line 2-2 assigned z z
Execute call setup processing for.

As is clear from the above description, according to this embodiment, after connecting the primary group interface subscriber lines 3-1 and 3-2 to the private branch exchange 8 equipped with a loopback section (LB) 831, the basic interface Telephone number DN from subscriber line 2-1 to primary group interface subscriber line 3-1:l
IS by simply making a test call with l as the incoming phone number.
Thirty more test calls are added to the DN exchange 1, including test calls arriving from the primary group interface subscriber [3-2 to the primary group interface subscriber line 3-1.

It should be noted that FIGS. 2 to 6 are only one embodiment of the present invention, and for example, the call return means 100 is not limited to the loopback path 7 and private branch exchange 8 shown in the figures, and may be used in other ways. Many modifications may be considered, but the effects of the present invention remain the same in any case. In addition, the ISD that is the subject of the present invention
It goes without saying that the N exchange 1 is not limited to what is illustrated.

[Effects of the Invention] As described above, according to the present invention, in the ISDN exchange,
With the return call originating means connected to the first and second primary group interface subscriber lines, the first Test calls corresponding to the number of B channels forming the primary group interface subscriber line of There is no need for the tester to spend a great deal of effort, and it becomes possible to easily perform high-load tests on the ISDN exchange.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a diagram showing a high load test method according to an embodiment of the present invention (claims 1 and 3), and Fig. 3 is a diagram showing the high load test method in Fig. 2. 4 is a diagram showing an example of a setting process, FIG. 4 is a diagram showing a high load test method according to an embodiment of the present invention (claims 2 and 3), and FIG. FIG. 6 is a diagram showing an example of the high load setting process in FIG. 5, and FIG. 7 is an example of a conventional high load test method. FIG. 8 is a diagram showing an example of another conventional high-load test method. In the figure, 1 is an ISDN exchange, 2 is a basic interface subscriber line, 3 is a primary group interface subscriber line, and 4 is an ISDN switch.
and 8 is a private branch exchange (PBX), 5 is an extension, 6 is a pseudo call generator CPCG), 1 is a loopback path, 11 and 81 are networks (NW), 12 is a digital terminal (DT), 13 and 83 are central Control device (C
C), 14 and 84 are main memory devices (MM), 15 is an automatic response device (AT), 82 is a central office line trunk (CT), 1
00 is a callback means, 141 is a multi-line selection table (M
HG), 200 is a plurality of subscriber continuous selection means, and 831 is a loopback unit (LB). Mokhi Susumu/) Principle diagram Figure 1 This invention (Job PR and rust point 3) L, Gl, G?荊Trial, Vinegar formula Ω Ω A Yuanmei (neck request section 2 and 〆ASTa kan section 3) commercial tribute fortune detail J good figure 4/7 1st edition of the history of Menge Aya Basashi!] The present invention (Fei Zhuang) and Fei Gusu 4)
To the opening ceremony, 1 eyebrow is drawn to the 5th figure. Xun Kun style island blooming style

Claims (4)

[Claims] (1) Basic interface subscriber line (2-1, 2-2)
and primary group interface subscriber lines (3-1, 3-2
), and in the call setup message transmitted to the terminating subscriber line (3-1) when a call is received, the terminating telephone number (DN_3
ISDN switch (1) equipped with the function of adding _1)
A call setup message in which the telephone number (DN_3_1) added to the call setup message sent from the ISDN exchange (1) to the first primary group interface subscriber line (3-1) is the called telephone number. from the second primary group interface subscriber line (3-2) corresponding to the first primary group interface subscriber line (3-1) to the IS
return calling means (100) for returning a call to the DN exchange (1); and the first primary group interface subscriber line (3-1).
holds the telephone number (DN_2_2) of the subscriber line to which the incoming call is transferred when the terminal is fully busy, corresponding to the telephone number (DN_3_1) of the first primary group interface subscriber line (3-1); and a plurality of subscriber consecutive selection means (200) for making a call from the test basic interface subscriber line (2-1) to the first primary group interface subscriber line (3-1). By doing so, until the first primary interface subscriber line (3-1) is fully busy, the second primary interface subscriber line (3-1) is connected to the second primary interface subscriber line (3-1) via the return calling means (100). 3-2) to the first primary group interface subscriber line (3-1), the plural subscriber consecutive selection means (200) selects the first primary group interface subscriber line (3-1). Line (3-1) phone number (DN_3_
A high load test method characterized by attempting to receive a call to the subscriber line specified by the telephone number (DN_2_2) held corresponding to 1). (2) The ISDN exchange (1) has the first primary group interface subscriber line (3-1) and the second primary group interface subscriber line (3-1) corresponding to the first primary group interface subscriber line (3-1). 1
2. The high-load test system according to claim 1, wherein a plurality of sets of the next group interface subscriber line (3-2) and the callback means (100) are provided. (3) The return calling means (100) connects the first primary group interface subscriber line (3-1) and the second primary interface subscriber line (3-1).
2. The high load test method according to claim 1, wherein the communication line is a communication line that connects back to the next group interface subscriber line (3-2). (4) The return call originating means (100) is configured to call back the IS using the first primary interface subscriber line (3-1) and the second primary interface subscriber line (3-2).
connected to the DN exchange (1), and connected to the ISDN exchange (1).
) to the first primary group interface subscriber line (3-1)
When receiving a call setup message to which the telephone number (DN_3_1) of the called subscriber line (3-1) is added, the call is sent to the telephone number (DN_3_1) added to the received call setup message. Edit a call setup message with a telephone number and send it to the first primary group interface subscriber line (3-3) accommodated in the ISDN switch (1).
2. The high-load test method according to claim 1, wherein the high-load test method is a private branch exchange that transmits data from a predetermined second primary group interface subscriber line (3-2) other than 1) to the ISDN exchange (1).