JPH03177145A - Call origination-termination test method - Google Patents

Abstract

PURPOSE:To realize a call origination and termination test at only its own station by looping back and inputting the output of a transmission terminal part including the D channels of two modes to it by a loop-back means, and exchanging the time slots of the D channels of two modes with each other by a D channel exchange part. CONSTITUTION:Plural D channels among looped back signals are sent to a multiple D channel terminal part 36 by the transmission terminal part 38. At that time (at the time of call termination), the D channel exchange part 37 exchanges the time slots. Namely, the time slots of the D channel of a network side mode and the D channel of a terminal mode are exchanged with each other. Thus, a call origination and termination test can be executed at only its own station by the loop-back of plural D channels and the exchange of their time slots without using a transmission device, a digital trunk line, and a remote party station, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This invention relates to a call originating/receiving test method for a station device including a trunk trunk accommodating a plurality of control signal channels.

The purpose is to enable testing of incoming and outgoing calls using only the own station.

A transmission termination section that multiplexes or separates a plurality of B channels and a plurality of D channels and interfaces with a transmission device, a plurality of D channel termination section that sets a mode of the plurality of D channels, and a plurality of D channels. a D channel exchange section for exchanging time slots; and a return means for returning the output of the transmission termination section and inputting it to the transmission termination section.

The plurality of D channel termination units set one of the plurality of D channels to a network side mode and the other one to a terminal side mode, and the loopback means sets one of the plurality of D channels to a terminal side mode.
The output of the transmission termination section containing the channel is input back to this, and the D channel exchange section is configured to exchange the time slots of the D channel of the two modes with each other.

[Industrial Field of Application] The present invention relates to a call testing method, and more particularly to a call testing method for a station device including a trunk trunk accommodating a plurality of control signal channels.

When connecting your own device such as a PBX to a digital trunk line (digital multiplex transmission line) via a transmission device.

It is necessary to perform a call/receive test on the local station device.

[Conventional technology]

In the digital multiplex interface, as a wide variety of services are being provided with the development of rsDN (Service Comprehensive Digital System), a common line signaling method is adopted that uses 7 common lines to send and receive control signals. Typical common line signaling systems in l5DN include the Hiroshi 7 common line signaling system and the D channel (control signal channel) common line signaling system (hereinafter referred to as the N[17 The common line signaling system will be explained as being included in the D channel common line signaling system).

FIG. 9 shows the configuration of a digital signal network in which each PBX (private branch exchange) 1 accommodating each user terminal is connected to a public R114P from each digital multiplex interface 3 via each transmission device 2. Ru. The digital multiplex interface 3 is 5, for example, 30 B channels and 1 D channel.
Consists of channels (30B+D), transmission speed is 2.04
8 M bps digital multiplex interface (hereinafter referred to as 2M multiplex interface), or 23 B
Consists of a channel and one D channel (23B+D),
There is a digital multiplex interface with a transmission speed of 1.544 M bps (hereinafter referred to as a 1.5 M multiplex interface).

Figures 10(a) and 1) show the data formats of 2M and 1.5M multiplex interfaces.
In the 2M multiplex interface of a), a channel (frame control channel) C for performing frame control is assigned to channel number (time slot) 00 on the transmission path, and a channel D for transmitting control signals is assigned to channel number 16. 30 line channels (voice/data channels) B for transmitting user information are allocated to channel numbers 01 to 15 and 17 to 31. In the 1.5M multiplex interface shown in FIG. 10(b), bit F for frame synchronization is assigned to the first focus on the transmission path, and channel number 23 is assigned.
Channel D is assigned to channel numbers OO to 22, and channel B is assigned for 23 channels.

However, 8 For example, in certain corporate communications.

When attempting to send and receive control signals by configuring a digital multiplex interface using an existing network, Figure 1O (a)
Or, as shown in (b), there are inconveniences when using a D channel with a fixed channel position.For example, as an existing transmission line, a total of five digital multiplex transmission lines such as three 5B+D, 4B+D, and 7B+D are terminated. However, if you want to connect to PBX 1 with a 2M multiplex interface, you will need to terminate 26 B channels and 5 D channels. However, the conventional 2M multiplex interface is fixed at 30B+D as shown in FIG. 10(a), and cannot support this.

Therefore, the present applicant first terminates various existing transmission lines, and even if the number of control signal channels to be terminated changes accordingly, each control channel is terminated flexibly and efficiently to create a digital multiplex interface. We proposed a technology that makes it possible to assign

The outline is explained below.

In a termination method for terminating a digital multiplex transmission path, first, multiple control channel signals are generated from multiple types of control signals, and each of the generated control channel signals is sent to an arbitrary number of time slots on the digital multiplex transmission path. The time slots are allocated to the control signal transmission channel (D channel or D channel transmitter) in a multiplexed manner. On the other hand, among the time slots on the digital multiplex transmission path, an arbitrary plurality of time slots are allocated to a control channel (D channel or D channel receiving section) to separate control channel signals. Then, a plurality of types of corresponding control signals are extracted from each separated control channel signal.

By doing this, 1. For example, when terminating a plurality of existing digital multiplex transmission lines in a specific company communication, etc., the control signal used depending on the terminating state is
After being converted into a control channel signal by the control channel signal generating means, it is multiplexed into a plurality of pre-assigned time slots of a digital multiplex transmission path by the control channel signal multiplexing means. Further, the control channel signal separating means and the control channel signal extracting means perform operations completely opposite to the above. Therefore, even if various existing transmission lines are terminated and the number of control signal channels to be terminated changes accordingly, each control channel can be terminated flexibly and efficiently and assigned to a digital multiplex transmission line. Become.

(Problem to be solved by the invention) 1); The applicant mentioned in 1! Even when using the technology developed by 2Higashi, a single call/reception test is always required.

FIG. 11 shows a method for testing incoming and outgoing calls onboard a ship.

When the PBX 1 of the local station A as the local station device is connected to a digital multiplex transmission path (digital relay &'il) via the transmission device 2, a primary call originating/receiving test is normally performed. That is, the telephone 31, which is the terminal for the own station, calls the telephone 31, which is the terminal for game B (7), and performs a voice call/receive test.
Further, the data terminal 32 of the game station B is called from the data terminal 32 of the own station to perform a data transmission/reception test.

According to such a test method, there is a problem in that in order to conduct the test, game B or a device equivalent to game B is always required. Furthermore, even if there is a game B, the construction dates for the own station A and game B must match, and the digital multiplex transmission line for connection must be available for use (actually, There is a problem in that it is rare that a digital multiplex transmission line (actual line) can be used at the time of testing.

In the present invention, when a plurality of D channels exist, as in the technique proposed by the applicant mentioned above, by utilizing this, regardless of the state of the game and the digital relay line,
This is based on the inventor's new knowledge that it is possible to test outgoing and receiving calls only at the own station.

SUMMARY OF THE INVENTION An object of the present invention is to provide a call testing method that allows testing of calls only at the own station.

[Means to solve the problem]

FIG. 1 is a diagram illustrating the principle of the present invention and shows nine trunk trunks according to the present invention.

In FIG. 1, 34 is a trunk accommodating multiple D channels;
Reference numeral 36 designates a plurality of D channel termination units, 37 a D channel exchange unit, 38 a transmission termination unit, and 39 a return means.

The multiple D channel termination section 36 sends out multiple D channels and sets a mode for each of them. This mode includes a network side mode that follows the signal content and signal sequence on the network (public network) side, and a terminal side mode that follows the signal content and signal sequence on the terminal side.

The D channel exchange section 37 is? Conversion of the time slots is performed for the D channels of j[number.

The transmission termination section 38 interfaces with the transmission device, allocates and multiplexes a plurality of B channels and D channels to a time slot, and also performs multiplexing.

Separate multiplexed things.

The loopback means 39 inputs (receives) the output (outgoing) of the transmission termination section 38 as it is to the transmission termination section 38. That is, the loopback means 39 is a means for connecting the output terminal and the input terminal of the transmission termination section 38. This is an alternative to playing a game in a one-call/receive test.

[For production]

In the call originating/receiving test, first, the multiple D channel termination section 36 sets at least one D channel to the network side mode, sets at least one other D channel to the terminal side mode, and sends it out to the two transmission termination section 38. At this time (at the time of transmission), the D channel exchange section 37 does not perform time slot conversion.

The transmission termination unit 38 multiplexes a plurality of B channels and a plurality of D channels, creates an interface similar to that used for sending out to a transmission device, and sends out the same.

The folding means 39 receives the output of the transmission termination section 38.

The signal is returned as it is and inputted to the transmission termination section 38.

Therefore, the time slots of the D channel, especially the D channel of the two modes mentioned above, also remain the same.

A plurality of D channels of the folded back signal are sent by a transmission termination section 38 to a plurality of D channel termination section 36 . At this time (when receiving a call), the D channel exchange unit 37 exchanges time slots.

That is, the time slots of the D channel in the network side mode and the D channel in the terminal mode are exchanged with each other.

As a result, the D channel sent out in the network side mode is connected to the D channel receiving section in the terminal mode,
The D channel sent out in the terminal mode is connected to the D channel receiving section in the network side mode. Therefore,
It is possible to simultaneously test incoming calls from the network to the terminal and outgoing calls from the terminal to the network. That is, a transmission device.

By using digital trunk lines, opposing stations, etc., it is possible to perform call testing only at the own station by turning back multiple D channels and exchanging their time slots.

Note that when there is only one D channel, such as in the conventional 30B+D and 23B+D, it is not possible to perform such a call/receive test only at the own station. This is because even if the output of the own station is input as is by the loopback means 39, the time slots cannot be exchanged because there is only one D channel.Therefore, even if the signal can be physically received by loopback, The mode is the same as when the call was made; that is, the D channel has different signal content and signal sequence between the network (public Y4) side and the PBX terminal side. After transmitting the D channel in terminal side mode, it is necessary to receive the D channel in network side mode. However, since the modes are the same, even though reception is possible, it is not possible to perform a formal call/receive test.

The present invention is made possible by focusing on and utilizing the existence of a plurality of D channels.

〔Example〕

FIG. 2 is a diagram showing the structure of the rope according to the embodiment.

PBX12 (12-1 to 12-
3) is connected to each transmission device 13 (13-1 to 13-3) by a digital multiplex interface 14 (14-1 to 14-3).

[Transmission devices] 3-1 to 13-3 are interconnected with other transmission devices by a plurality of existing transmission paths each having a different transmission speed, without going through a public network.

For example, the transmission device 13-1 is connected to other transmission devices 13-2 and 13-3 through a plurality of existing transmission paths consisting of a first path 15-1 to a fifth path 15-5. Each route 15-1 to 15-5 is.

Each is 5B 10, 4B 10, 5B 10, 7B+D.

It has a channel configuration of 5B10. The digital multiplex interface 14-1 has a channel configuration of 26B+5D. In addition, the digital multiplex interface 14
-2 is 21B+30. Digital multiplex interface 14
-3 is 27B+4D, and time slots can be flexibly assigned to combinations of B and D channels according to the termination status of each transmission word w13-1 to w13-3.

FIG. 3 is a configuration diagram of an embodiment, and particularly shows the calling and receiving functions of PBX I2 separately. Needless to say, one PBX 12 has both the functions of a calling side and a receiving side.

On the transmitting side, the control channel signal generating means 4 generates a plurality of control channel signals 7 from a plurality of types of control signals 6. That is, a frame signal based on a high-level data link procedure is generated as a control channel signal 7 from a plurality of types of control signals 6 such as call control signals.

The control channel signal multiplexing means 5 assigns each control channel signal 7 to an arbitrary plurality of time slots among the time slots on the digital multiplex transmission channel to a control signal transmission channel or a D channel (D channel transmitter). become For this purpose, the control channel signal multiplexing means 5 includes a memory for temporarily holding a frame signal, which is the control channel signal 7 outputted from the control channel signal generating means 4, and a pre-allocated plurality of digital multiplex transmission paths. A timing generation circuit that generates a timing signal that becomes active in the time slot of It consists of a selector, etc. that multiplexes data into empty time slots.

On the receiving side, the 5 control channel signal separation means 9 allocates arbitrary and plural time slots among the time slots on the digital multiplex transmission path to the control signal receiving channel or the D channel (D channel receiving section). Separate.

That is, for example, it has a configuration opposite to that of the control channel signal multiplexing means 5, and separates the user information 11 and the control channel signal 7.

The control channel signal extraction means 10 extracts a plurality of types of corresponding control signals 6 from each 111m channel signal 7 separated by the control channel signal separation means 9. Therefore, it has a configuration opposite to that of the control channel signal generating means 4 described above.

FIG. 4 is a block diagram of an embodiment, and particularly shows the self-originating/receiving test function of the PBX 12.

PBX12g! , terminal t, r, it busy 31 (311
, 3l-2) and data terminal 32 (32-1゜32-2)
) to accommodate. Voice/data information from the telephone 31 and the data terminal 32 is sent to multiple D via the network 33.
The information is sent to the channel accommodation trunk 34 as user information 11.

The network 33 connects the busy 31 and data terminals 32 to others according to the control signal 6.

The B channel exchange section 35? The time slots are exchanged for 31 B channels.

The multiple D channel termination unit 36 includes a control channel signal generating means 4 and a control channel signal extracting means 1O, and further has a function of setting a mode when generating a control channel signal.

The transmission termination section 3B consists of a control channel signal multiplexing means 5 and a control channel signal separating means 9.

The B channel exchange unit 35 and the D channel exchange unit 37 do not operate during normal call origination/reception, but perform time slot exchange processing only for returned signals during a single call/reception test.

The return means 39 is for returning the signal sent from the PBX 12 to the transmission device 13.

Therefore, it has the same configuration as the digital multiplex interface 14.

FIG. 5 is an explanatory diagram of the transmission function.

Each user information 11 is multiplexed into the time slot of the B channel from the terminals 31 and 32 via the network 33 in the format shown in {circle around (2)} in FIG. 5, and is input as a B channel signal Bch. At this time, B channel exchange section 3
5 is 1. During both normal operation and testing, time slots are not exchanged during 1 transmission.

On the other hand, control signals 22 such as call control signals generated within the PBX 12 by the Dch processing unit 20 are input to the multiple Dch processing circuit 16, where they are assembled into a frame signal 23 in HDLC (high level data link procedure) format. It will be done.

This Dch processing section 20.

This is realized in software by a central processing bag W (not shown) in the PBX 12 and a processing program.

The frame signal 23 is output via the digital multiplexing circuit 17 as the D channel signal Dch shown in FIG. At this time, the D channel exchange unit 37 does not exchange time slots during one transmission in either normal operation or testing.

These B channel signals Bch in the formats shown in Figure 5 ■ and ■
and the D channel signal Dch is sent to the Dch insertion selector 1.
9, and the multiplexed signal in the mB+nD format shown in FIG.

The Dch insertion selector 19 selects the D channel signal Dch from the digital multiplexing circuit 17 at the timing when the timing signal 40 output from the Dch insertion timing generation circuit 1 becomes active.

At other timings, the B channel signal Bch is selected.

The operations of the digital multiplexing circuit 17 and the Dch insertion timing generation circuit 18 are controlled by the multiplexing control section 21. The multiplexing control unit 21 is realized as software using a central processing unit and a processing program.

FIG. 6 is an explanatory diagram of the receiving function.

mB of ■ from the transmission device 13 or return means 39 in FIG.
Among the multiplexed signals input in the +nD format, the B channel signal Bch is transferred to predetermined terminals 31 and 32 (not shown) via the network 33.

At this time, the B channel signal passes through the B channel exchange section 35. In normal operation, the B channel signal passes through the B channel exchange section 35.
In this case, time slots are not exchanged. On the other hand, in the two-call/receive test, the B channel exchange unit 35 exchanges time slots with multiple B channels corresponding to the D channel set to the network side mode. , with a plurality of B channels corresponding to the D channel placed in terminal mode.

Swap their time slots with each other.

On the other hand, the D channel signal Dch is separated from the B channel signal Bch in the digital multiplexing and demultiplexing circuit 24 operating under the control of the 1 separation control section 26, and the 0 separation control section 26 extracts it as a frame signal 23.

It is realized as software by a central processing unit and a processing program.

The frame signal 23 is sent via the D channel exchange section 37.
In normal operation, the D channel exchange unit 37 sends 0 to the multiple Dch processing circuit 25.

No exchange of time slots is performed.On the other hand, in the single call/reception test, the D channel exchange unit 37 exchanges 8 time slots, that is, the D channel set to network side mode and the D channel set to terminal mode. and exchange their time slots with each other. D channel exchange section 37
Let the output be a frame signal 23'.

The frame signal 23' is input to the multiple Dch processing circuit 25, and is decomposed into the control signal 22 by a process completely opposite to that of the aforementioned multiple Dch processing circuit 16 (FIG. 5).

This control signal 22 is processed by a Dch processing unit 27 on the receiving side to perform call control and the like. The Dch processing unit 27 is operated by a central processing unit and a processing program.

Realized as software.

The normal calling/receiving operation of the embodiment with the above configuration will be explained below.

First, as shown in Figure 5, a game (multiple games may be possible)
The content of each control signal 22 to be transmitted to is set by the Dch processing unit 20. Each control signal 22 includes content for setting the D channel to terminal mode.

The control signal 22 is set to H in the vl number Dch processing circuit 16.
The signal is formatted into a DLC format frame signal 23. The frame signal 23 is transmitted to the digital multiplex circuit 17
The data is stored in an internal memory (not shown) for a period of time.

On the other hand, from the Dch insertion timing generation circuit 18.

B input to the PBX 12 under the control of the multiplexing control unit 21
Timing signal 40 that becomes active at the timing of an empty channel to which channel signal Bch is not assigned
is output.

At the same time, at the above active timing.

Frame signal 2 temporarily held in digital multiplex circuit 17
3 is read out as the D channel signal Dch.

Furthermore, the Dch insertion selector 19 selects the D channel signal Dch read out from the digital multiplexing circuit 17 at the active timing.

Then, at a timing other than the above-mentioned active timing, the Dch insertion selector 19 outputs the B channel signal Bc.
Select h.

By the above operation, a multiplexed signal mB+nD ((■) in FIG. 5) in which the B channel signal Bch and the D channel signal Dch are allocated at an arbitrary preset ratio is output.

For example, the transmission bag ff13-1 in FIG.
-1 to 5th route 15-5, respectively.

5B+D, 4B+D, 5B+D, 7B+D, 5B(-D
When a plurality of existing transmission lines having a channel configuration are connected to one end of P, the digital multiplex interface l4-1 is assigned channel numbers 06, 11, 16, etc. as shown in FIG. 7(a).
A D channel signal Dch was multiplexed onto 25 and 31.

It can be a 2M multiplex interface. On the other hand, as the digital multiplex interface 14-2 in FIG.
As shown in Figure 7 (L)).

D channel signal Dc for channel numbers 05, 16 and 23
h was multiplexed. It can be 1.5 M multiplexed interfaces.

Each of the above settings applies to the multiplex control unit 2 of each PBX l 2.
1 can be freely set.

On the other hand, on the receiving side, the operation is completely opposite to that on the transmitting side.

That is, as shown in FIG. 6, in the digital multiplexing M circuit 24, the timing signal 4 of FIG.
A timing similar to 0 is occurring. As a result, the D-channel signal Dch inputted via the digital multiplexing interface 14 is transferred to a memory (not shown) in the digital multiplexing/demultiplexing circuit 24 in a completely opposite operation to that of the digital multiplexing circuit 17 in FIG. When it is taken in.

The D channel signal Dch is then input in the form of a frame signal 23 to a multiple Dch processing circuit 25, where the control signal 22 is taken out.

Thereby, the D channel signal Dch can be extracted from the arbitrary format multiplexed signal mB+nD inputted from the digital multiplexing interface 14.

Next, the operation during the 9 call/reception test will be explained.

In the following explanation, a case will be described in which 5 self-call/receive tests are performed on the PBX 12-1 shown in FIG. 2.

During testing, the folding means 39 is attached to the PBX 12-1. As a result, the output of the PBX 12-1 is looped back as is and is used as one input.

Also, for the test, the first 15 channels out of 30 (31) channels were designated as group A.

The mode of the corresponding D channel is set to network side mode, and the channel setting is set to 148+ID.

Furthermore, the latter 15 channels are designated as Group B.

Set the mode of the corresponding D channel as terminal mode.

Set the channel to 148+ID. This setting is
The channel processing section 20 and the multiplexing control section 21 can freely perform the processing.

The following will mainly refer to FIGS. 4 and 8.

The operation of the 0 call/receive test, which will be explained step by step, is basically performed using 1 normal operation.

A signal from the terminal 31 or 32 accommodated in the PBX 12-1 is transmitted as a B channel via the network 33.
The signal is input to the B channel exchange section 35. The time slot of the B channel for 35 people in the B channel exchange section is shown in Figure 8 (
a) (corresponding to ■ in Figure 5) As shown. The channel that should be the D channel is an empty channel.

Thereafter, the B channel is output from the B channel exchange section 35.

The signal is sent to the transmission termination section 38. The time slot of the B channel at this time is as shown in FIG.
Equivalent to figure (a).

On the other hand, the control signal 22 is
The content is such that the channels are set to network side mode and terminal side mode, respectively. Multiple D channel termination section 3
The time slot of the D channel sent out from the 8th
As shown in Figure (C).

In this time slot, the D channel No. 100 is in network side mode, and the D channel No. 01 is in terminal mode. Thereafter, the D channel is sent from the D channel exchange section 37 to the transmission termination section 38. The time slot of the D channel at this time is as shown in FIG. 8(8), and is equal to FIG. 8(C).

The transmission termination section 38 multiplexes the B channels and D channels shown in FIGS. 8(e) and (6).

It is sent out as the 2M multiplex interface shown in FIG. 8(f).

This sent signal is returned as it is by the return means 39 and inputted to the transmission termination section 38 .

The transmission termination unit 38 separates the B channel and the D channel, and connects each to the B channel exchange unit 35 and the D channel exchange unit 3.
Send to 7. The time slots at this time are equal to those in FIG. 8(e) or (a) and FIG. 8(c), respectively.

The B channel exchange unit 35 switches the B channel of the A group (B
oo to B13) and 8 channels of B group (B'0
0 to B'13'). That is, rB'00 to B'13J are set as the 8 channels of group A in this order.

rBOo to B13J are set as B channels of B group in this order to obtain the time slots shown in FIG. 8(b).

On the other hand, the D channel exchange unit 37 exchanges the time slots between the D channel (Doo) of group A and the D channel (DOI) of group B.

That is, "rDOl" in the terminal side mode is set as the D channel of group A, and "rDoo" in the network side mode is set as the D channel of group B, to obtain the time slot shown in FIG. 8(d).

As described above, the D channel in the network side mode is connected to the D channel receiving section in the terminal side mode, and the D channel in the terminal side mode is connected to the D channel receiving section in the network side mode.

For example, rB of group A, which is network side mode.
Calls using the O2J channel are made in terminal mode B.
For the group, it will be a station arrival on the rB'02J channel. Also, the call using the B group's rB'03J channel is called rBO3J for the A group.
This will be a local broadcast to the channel. This makes it possible to test calls from, for example, telephone 31-1 to telephone 31-2 and from data terminal 32-1 to data terminal 32-2, as shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, by using a plurality of D channels, it is possible to return its own signal as is and to exchange time slots of D channels with different modes. It is possible to perform incoming and outgoing tests on the own station without requiring a digital multiplex transmission line, a playing station, or equipment equivalent to the playing station, which greatly contributes to improving work efficiency when adding 5 new lines.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention. FIG. 2 is a network configuration diagram of the embodiment. FIG. 3 is a configuration diagram of an embodiment. FIG. 4 is a configuration diagram of an embodiment. FIG. 5 is an explanatory diagram of the transmission function. FIG. 6 is an explanatory diagram of the receiving function. FIG. 7 is a diagram showing an example of channel allocation in this embodiment. FIG. 8 is a diagram showing time slots. FIG. 9 is a configuration diagram of a general digital signal network. FIG. 10 is a diagram showing an example of general channel allocation. FIG. 11 is a diagram showing a general call testing method. 34 is a trunk for accommodating multiple D channels, 36 is a multiple D channel termination section, and 37 is a D channel exchange section. 38 is a transmission termination section, and 39 is a return means.

Claims (1)

[Claims] A call originating/receiving test method for a station device connected to a digital multiplex transmission path via a transmission device, comprising: multiplexing or separating a plurality of B channels and a plurality of D channels; a transmission termination section (38) that interfaces with the above; a multiple D channel termination section (36) that sets the mode of the plurality of D channels; and a D channel exchange section (37) that performs time slot conversion of the plurality of D channels. and a loopback means (39) for folding back the output of the transmission termination section (38) and inputting it to the transmission termination section (38), wherein the plurality of D channel termination section (36) is configured to output one of the plurality of D channels. One is set to network side mode, and the other one is set to network side mode.
one mode is on the terminal side, the loopback means (39) loops back and inputs the output of the transmission termination section (38) including the D channel of the two modes, and the D channel exchange section (37) D of two modes
A call/receive test method characterized by exchanging time slots of channels with each other.