JP3046752B2 - ISDN bus wiring checker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a confirmer for confirming whether or not bus wiring is normal after an ISDN is opened or expanded.

[0002]

2. Description of the Related Art Conventionally, a bus wiring test has been performed after the construction work of opening or adding an ISDN bus wiring.
The checker (ISDN bus wiring checker) that performs this test is
It has already been manufactured and sold, and the test method for the checker is roughly classified into the following two types.

FIG. 7 shows a conventional ISDN bus wiring checker 3
A service digital line connection unit DSU for ISDN,
FIG. 3 is a diagram showing an ISDN bus wiring BL1, a communication connector C1, and the like.

In FIG. 7, an ISDN bus wiring BL1,
After constructing BL2, BL3,..., As shown by the crosses in FIG.
L1 is removed, and the removed bus wiring BL1 is replaced with a checker T1 as shown by a broken line in FIG.
The checker T2 is connected to the first connector connection portion C1a, and it is confirmed that the bus wiring BL1 is normally connected.

In the same manner as described above, the communication connector C
The connector T2 is connected to the connector C2a of No. 2 to confirm that the bus wiring BL2 is normally connected, and to confirm that each of the bus wirings BL3,... Is normally connected. . After that, the bus wiring BL1 is reconnected to the connection device DSU.

FIG. 8 shows a conventional ISDN bus wiring checker 4.
A service digital line connection unit DSU for ISDN,
FIG. 3 is a diagram showing an ISDN bus wiring BL1, a communication connector C1, and the like.

In FIG. 8, bus lines BL1, BL2,
After installing BL3,..., The home device TS is connected to the connector connection portion C1a of the communication connector C1, and the confirmer T3 is connected to the connector connection portion C2a of the communication connector C2.
A line connection communication test is executed via the digital line connection device DSU. In this case, the conventional ISDN bus wiring checker 4 uses the monitor method to provide the bus wirings BL1, BL
Confirm that 2 has been connected normally.

[0008] In this case, even if a part of the bus line BL1 is incorrect, communication using the in-home device TS is possible. That is, since the transmission code used in the I interface is a bipolar signal called AMI (Alternate Mark Inversion), the digital line connection device DS
When the signal lines (signal lines in the terminal direction) to be connected to the terminals RA and RB of the U and the terminals RA and RB of the communication connector C1 are crossed (DSU
Is connected to the terminal RA of the communication connector C1 and the terminal RB of the digital line connection device DSU is connected to the terminal RA of the communication connector C1), and the positive pulse (or the negative pulse) is inverted. However, since there is no problem as a transmission code, no abnormality occurs in the operation.

[0009] However, the digital line connection device DSU and each terminal are connected to the information channel bit B via the bus wiring.
A frame (48 bits per frame) in which bits necessary for synchronization, control, and the like are added in addition to 1, B2, and the signal system channel bit D are synchronously transmitted and received. This synchronization
The terminal detects and performs a frame synchronization bit (F bit) transmitted by the digital line connection device DSU, so that two terminals can simultaneously communicate with the information channels B1 and B2.

Since the transmission code used in the I interface is a bipolar signal called AMI, 0 of data is represented by a positive or negative pulse. Therefore, even when the bus wiring is cross-connected to the terminals TA and TB and the bus wiring is cross-connected to the terminals RA and RB, when the terminals simultaneously communicate, the terminals can normally detect the synchronization. However, the synchronizing signal that is looped back from the terminal TB to the digital line connection device DSU disappears due to the overlap of the positive pulse and the negative pulse, and an abnormality occurs in which the synchronization bit (F bit) does not reach the digital line connection device DSU. . However, if the terminals TA and TB are normally connected, and the terminals RA and RB are cross-wired, the F bit normally reaches the digital line connection device DSU, so that there is no abnormality in the operation. No abnormalities can be found in the connection test in. That is, the terminal TA,
The wires are crossed between TBs, and the terminals RA, R
If a plurality of terminals communicate simultaneously when a line is crossed between B, even if the ISDN bus wiring checker 4 is used, the cross wiring cannot be found. Therefore, even in the ISDN bus wiring confirmation device 4, it is not possible to find an erroneous wiring of the bus wiring BL1.

[0011]

As described above, in the conventional ISDN bus wiring checker 3, the connection is disconnected after the bus wiring is performed, and there is a possibility that an error may occur when the wiring is re-installed. There is.

Further, in the conventional ISDN bus wiring confirmation device 4, it is necessary to perform line connection communication after the construction of the bus wiring and before the confirmation, so that the confirmation of the bus wiring BL1 cannot be made, and the bus wiring is completely removed. There is a problem that cannot be confirmed. Further, in the conventional ISDN bus wiring checker 4, the terminals TA and TB are normally connected,
Even if wires are crossed between terminals RA and RB,
There is a problem that it cannot be found that the wiring is crossed.

The present invention provides a bus wiring checker which can completely confirm the bus wiring to be performed after the ISDN opening work or the extension work is completed, and which can be reduced in size and weight and is portable. The purpose is to do so.

[0014]

According to the present invention, an ISDN bus wiring comprises a first line, a second line, a third line, and a fourth line, and a first line corresponding to the first line. A first DC power supply B1 for applying a voltage between the first terminal and the second terminal corresponding to the second line, and a third terminal corresponding to the third line and the fourth terminal corresponding to the fourth line. And a second DC power supply B1 for applying a voltage between the terminals and a terminal of the ISDN service digital line connection device.
A voltage is applied between the first terminal and the second terminal, and a third DC power supply B3 connected in series to the first light emitting unit, and a third terminal connected between the third terminal and the fourth terminal. A fourth DC power supply B4 connected in series to the second light-emitting unit;
And a third light-emitting unit that emits light by a voltage applied between the third terminal and the third terminal, and a detection unit connected to the connector connection unit of the communication connector.

[0015]

FIG. 1 shows an ISDN bus wiring checker 1 according to one embodiment of the present invention, together with an ISDN service digital line connection device DSU, an ISDN bus wiring BL1, a communication connector C1, and the like. FIG.

First, in FIG. 1, a digital line connection device DSU for ISDN service and a plurality of communication connectors C
, 1, C2, C3,... Are connected by ISDN bus wiring. That is, the digital line connection device DSU and the communication connector C1 are connected by the ISDN bus wiring BL1, the communication connectors C1 and C2 are connected by the ISDN bus wiring BL2, and the ISDN bus wiring BL
3, the communication connectors C2 and C3 are connected.

The bus line BL1 is connected to the first line L1,
The second line L2, the third line L3, and the fourth line L4 are formed. Similarly, the bus line BL2 is also formed of the first line L1 to the fourth line L4, and the bus line BL3 is also formed of the first line L4. Line L1 to 4th
This is constituted by the line L4.

If the bus wiring BL1 is correctly wired, as shown in FIG.
U and a first terminal T of the communication connector C1.
A is connected by the first line L1, the second terminal TB of the digital line connection device DSU and the second terminal TB of the communication connector C1 are connected by the second line L2, and the digital line connection device DSU The third terminal RA and the third terminal of the communication connector C1
Are connected by a third line L3, and the fourth terminal RB of the digital line connection device DSU and the fourth terminal RB of the communication connector C1 are connected by a fourth line L4. Further, if the other bus lines are wired normally, as shown in FIG. 1, the first terminal TA of one communication connector and the first terminal TA of the next communication connector are connected to the first line L1. , The second terminal TB of one communication connector and the second terminal TB of the next communication connector are connected by a second line L2, and the third terminal RA of one communication connector and the next communication are connected. A third terminal RA of the connector is connected by a third line L3,
The fourth terminal RB of one communication connector and the fourth terminal RB of the adjacent communication connector are connected by a fourth line L4.

The ISDN bus wiring checker 1 performs the above-mentioned ISDN bus wiring after the opening or the extension of the ISDN bus wiring.
This is a checker for checking that the DN bus wiring is normal, and includes a voltage applying unit 10 and a detecting unit 20.

The voltage application unit 10 includes a first DC power supply B1
And a second DC power supply B2 and a connector 10a.

The first DC power supply B1 is a power supply for applying a voltage between the first terminal TA corresponding to the first line L1 and the second terminal TB corresponding to the second line L2. The second DC power supply B2 is connected to a third terminal RA corresponding to the third line L3.
And a fourth terminal RB corresponding to the fourth line L4. The connector 10a is a connector DS in the digital line connection device DSU for ISDN service.
This is a connector connected to Ua.

The detecting section 20 includes a third DC power supply B3, a fourth DC power supply B4, and a first light emitting diode LED1.
, A second light emitting diode LED2, a third light emitting diode LED3, a voltage adjusting circuit AD, and a connector 20.
a.

The third DC power supply B3 applies a voltage between the first terminal TA and the second terminal TB, and is a power supply connected in series to the first light emitting diode LED1, and a fourth DC power supply B3.
DC power supply B4 is a power supply that applies a voltage between the third terminal RA and the fourth terminal RB and is connected in series to the second light emitting diode LED2. The third light emitting diode LED3 is a light emitting diode that emits light by a voltage applied between the second terminal TB and the third terminal RA. The connector 20a has communication connectors C1, C2, C
3 is a connector connected to the connector connection portions C1a, C2a, and C3a.

Note that, from the digital line connection device DSU,
A plurality of home appliances are connected via the communication connectors C1, C2, C3,..., And two pairs of metallic cables are used between the digital line connection device DSU and the communication connectors C1, C2, C3,. It is constructed with the bus wiring that was used.

FIG. 2 shows an ISD according to another embodiment of the present invention.
FIG. 2 is a diagram illustrating an N bus wiring checker 2 together with an ISDN service digital line connection device DSU, an ISDN bus wiring BL1, a communication connector C1, and the like.

In FIG. 2, a digital line connection device DS
The relationship between U, the bus wiring BL1, and the communication connector C1 is the same as that in FIG. 1, but the communication connector C2 and the subsequent parts are omitted, and a communication connector CR with a terminating resistor is described instead. Also, the ISDN bus wiring checker 2 is basically the same as the ISDN bus wiring checker 1,
More specifically, the ISDN bus wiring checker 2 is described than the DN bus wiring checker 1.

The digital line connection device DSU includes a signal receiving circuit RE, a signal transmitting circuit TR, and a power supply circuit PU.
And The signal receiving circuit RE has a coil and a terminating resistor, the signal transmitting circuit TR has a coil and a terminating resistor, and the signal receiving circuit RE and the signal transmitting circuit TR in FIG.
Shows only the primary coil, the secondary coil is omitted, and signals are transmitted through the secondary coil to the communication lines PL1 and PL1.
It is transmitted to PL2. The power supply circuit PU includes a communication line P
It converts the voltage supplied to L1 and PL2 to, for example, 40V.

After the ISDN bus wiring is opened or expanded, the ISDN bus wiring checker 2 is used.
This is a checker for checking that the DN bus wiring is normal, and includes a voltage application unit 11 and a detection unit 21.

The voltage applying section 11 includes a first DC power supply B1
, A second DC power supply B2, resistors R1 and R2, diodes D1 and D2, and a connector 11a.

The first DC power supply B1 is, for example, 1.5 V
And + is applied to the first terminal TA corresponding to the first line L1.
The second terminal T is connected to the second terminal T corresponding to the second line L2.
This is a power supply having a negative terminal connected to the B side. Second DC power supply B2 is, for example, 1.5 V, has a + terminal connected to third terminal RA corresponding to third line L3, and a fourth terminal RB corresponding to fourth line L4. Is a power supply to which the-terminal is connected.

The diode D1 is connected in series and forward with the first DC power supply B1, and the resistance R1 is, for example, 2Ω.
And are connected in series with the diode D1. The diode D2 is connected in series and forward with the second DC power supply B2, and the resistor R2 is, for example, 2Ω and is connected in series with the diode D2.

The connector 11a is a connector connected to the connector DSUa in the ISDN service digital line connection device DSU.

The detection unit 21 includes a third DC power supply B3, a fourth DC power supply B4, and a first light emitting diode LED1.
A second light emitting diode LED2, a third light emitting diode LED3, a fourth light emitting diode LED4,
It has diodes D3 and D4, resistors R3 and R4, a voltage adjustment circuit AD, and a connector 20a.

The third DC power supply B3 is, for example, 1.5 V
And-on the first terminal TA side corresponding to the first line L1.
The second terminal T is connected to the second terminal T corresponding to the second line L2.
This is a power supply with the + terminal connected to the B side. The fourth DC power supply B4 has, for example, 1.5 V, a negative terminal connected to the third terminal RA corresponding to the third line L3, and a fourth terminal RB corresponding to the fourth line L4. Is a power supply to which the + terminal is connected.

The light emitting diode LED1 is connected in series and forward with the third DC power supply B3, and the resistor R3 is, for example, 500Ω and is connected in series with the light emitting diode LED1. The light emitting diode LED2 is connected in series and forward with the fourth DC power supply B4, and the resistance R4 is
For example, it is 500Ω, and is connected in series with the light emitting diode LED2.

The diode D3 has its cathode connected to the first terminal TA, its anode connected to the second terminal TB, and the diode D4 has its cathode connected to the third terminal RA and its anode connected. It is connected to the fourth terminal RB.

The voltage adjustment circuit AD includes a varistor VR
(For example, for 30 V) and a resistor R6 connected in series to the varistor VR.
Is connected between the second terminal TB and the third terminal RA. Note that the connection position of the voltage adjustment circuit AD is not limited to the above position, and the terminals TA,
The voltage adjustment circuit AD may be connected between one of the terminals TB and one of the terminals RA and RB.

The connector 21a includes communication connectors C1, C
2, C3,... Connector connection portions C1a, C2a, C3
a,... are connectors to be connected.

That is, the first DC power supply B1 and the third DC power supply B3 are connected in series with each other via the normally connected first line L1 and second line L2. The third DC power supply B3 and the fourth DC power supply B4 are connected in series to each other via a third line L3 and a fourth line L4 that are normally connected.

Next, the operation of the ISDN bus wiring checker 2 will be described.

FIG. 3 is a flowchart showing the operation of the ISDN bus wiring checker 2.

First, the connector 11a of the voltage application unit 11 and the connector 21a of the detection unit 21 are connected to each other (S
1) Check the degree of consumption of the power supplies B1 and B2. In this case, the terminals TA, TB, RA, and RB are connected. When connected in this manner, the light emitting diode L
If at least one of the ED1 and the LED2 does not light (S2), the power supply corresponding to the light emitting diode that does not light is replaced with a non-defective one.

On the other hand, the light emitting diodes LED1, LED2
Are both lit (S2), the state of bus wiring construction can be reliably determined, and the digital line connection device DSU
The connector 11a of the voltage applying unit 11 is connected to the connector DSUa installed inside the device (S11), and between the first terminal TA and the second terminal TB, and between the third terminal RA and the fourth terminal TB. A voltage is applied between the terminal and the terminal RB. Then, the number n of the communication connectors is initialized to “1” (S12), and the bus wiring B
The connector 21a of the detection section 21 is connected to the connector connection section C1a of the communication connector C1 to which L1 is connected (S13).

At this time, the light emitting diodes LED1, L
The lighting status of ED2 and LED3 is checked (S14). At least one of light emitting diodes LED1, LED2, LED3
If one of them is turned off, the erroneous wiring of the bus line corresponding to the turned off light emitting diode is repaired (S1).
5). The relationship between the light-emitting diode that is turned off and the erroneous bus wiring will be described later.

When the restoration is completed or when all of the light emitting diodes LED1, LED2, and LED3 are turned on, the number n of the communication connectors is incremented by 1 (S17), and the above series of operations (S13 to S15, S1
7) is repeated (S16), and the process ends when the number n of communication connectors reaches the set number N of communication connectors.

Next, the light emitting diodes LED1, LED
2, a light emitting diode that is turned off among the LEDs 3,
The relationship with the incorrect wiring in that case will be described.

FIGS. 4 to 6 show an ISDN bus wiring checker 2
, Light emitting diodes LED1, LED2, LED
FIG. 4 is a diagram showing a relationship between a light-emitting diode that is turned off in 3 and an incorrect wiring in that case.

4 to 6, the light emitting diode LE
A mark on the right of D1 to LED3 indicates that the light is on, and a mark x indicates that the light is off. In addition, the voltage application unit 11 is described in the digital line connection device DSU for convenience, and the digital line connection device DSU
FIG. 6 is a diagram in a case where attention is paid to a bus line BL1 that connects the communication connector C1 to a bus.

FIG. 4A shows a case where the bus line L1 is normally connected.
All of the LEDs 3 are turned on. FIG. 4B illustrates a case where the terminals TA and TB are connected, the terminals RA and RB are connected, and there are two sets of cross wirings.
ED1 and LED2 are turned off. FIG. 4 (3) shows the terminal T
FIG. 13 is a diagram illustrating a case where B and RA are connected and a set of cross wirings is present, in which all of the light emitting diodes LED1 to LED3 are turned off.

FIGS. 5 and 6 also show the relationship between the connection state of the bus wiring and the light-off state of the light emitting diode. Judging from FIGS. 4 to 6, the light emitting diode LED
The case where only 1 is off is the case of FIG. 5 (1), and the case where only the light emitting diode LED2 is off is the case of FIG. 5 (3).
When only the lights are turned off, FIG. 5 (2), FIG. 6 (1),
This is the case of (2). FIG. 4B shows the case where only the light emitting diodes LED1 and LED2 are turned off, and FIG. 4C or FIG. 6 if all the light emitting diodes LED1 to LED3 are turned off. This is the case of (3). Therefore, it is possible to easily and reliably grasp the connection state of the bus wiring based on the light-off state of the light emitting diode.

First DC power source B1, second DC power source B
2, the series resistance connected to each of the third DC power supply B3 and the fourth DC power supply is a light emitting diode LED1,
This limits the voltage applied to the LED 2. First
It is sufficient that a series resistor is connected to at least one of the DC power source B1, the second DC power source B2, the third DC power source B3, and the fourth DC power source.

The diodes D1 and D2 are connected in series with the first DC power supply B1 and the second DC power supply B2, respectively. The diodes D1 and D2 reduce the voltage applied to the light emitting diodes LED1 and LED2. Restrict. The first DC power supply B1, the second DC power supply B2, the third
DC power supply B3, at least one of the fourth DC power supply,
It suffices if a diode is connected.

The voltage adjusting circuit in series with the third light emitting diode LED3 is an example of a voltage drop element.

In FIG. 2, the fourth light emitting diode L3 is arranged in parallel and in the opposite direction to the third light emitting diode LED3.
Although the ED 4 is connected, the fourth light emitting diode LED4 is turned on when the power supply circuit PU generates a voltage in a direction opposite to the normal direction.

In the above embodiment, if an overcurrent flows through the circuit components of the digital line connection device DSU for the ISDN service, it has an adverse effect.
The circuits 0 and 11 are set to currents and voltages that do not adversely affect the above.

In the above embodiment, the normality of the bus wiring can be confirmed without disconnecting the connection after the bus wiring is constructed, and the normality of the bus wiring can be confirmed without communication. Moreover, the checking operation is simple, and the normality of the bus wiring can be reliably checked. Further, in the above embodiment, since the circuit is simple, the entire bus wiring confirmation device is small and lightweight, and it is convenient to carry.

In FIG. 2, the ISDN bus is set by setting the output voltage of the PU to a value other than 40 V or changing the value of current that can be passed through the coil in the signal receiving circuit RE and the coil in the signal transmitting circuit TR. Resistances R1, R2, R3, R4, diodes D1, D2 in wiring checker 2
Can be omitted. Also, DC power supplies B1, B2,
All the polarities of B3 and B4 may be set opposite to the polarities shown in FIG. A comprehensive embodiment in such a case is shown in FIG. 1 as an ISDN bus wiring checker 1. When all the polarities of the DC power supplies B1, B2, B3, and B4 are set to be opposite to the polarities shown in FIG. 2, the polarities of the light emitting diodes LED1, LED2, LED3, and LED4 are also opposite to the polarities shown in FIG. Must be set. Further, the resistances R1 and R1 in the ISDN bus
Any one or some of R2, R3, R4 and diodes D1, D2 may be omitted.

Further, DC power supplies B1, B2, B3, B4
Voltage value, resistance values of resistors R1, R2, R3, R4, PU
May be set to a value different from the above. Further, in each of the above embodiments, another light emitting unit may be used instead of the light emitting diode.

[0059]

According to the present invention, it is possible to completely confirm the bus wiring to be performed after the construction work of the ISDN is opened or expanded, and it is possible to reduce the size and weight of the bus, and it is convenient to carry. To play.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an ISDN bus wiring checker 1 according to an embodiment of the present invention.
FIG. 3 is a diagram showing a U, an ISDN bus line BL1, a communication connector C1, and the like.

FIG. 2 shows an ISDN bus wiring checker 2 according to another embodiment of the present invention, using an ISDN service digital line connection device D;
FIG. 3 is a diagram showing an SU, an ISDN bus wiring BL1, a communication connector C1, and the like.

FIG. 3 is a flowchart showing the operation of the ISDN bus wiring checker 2;

FIG. 4 is a diagram showing a relationship between a light emitting diode that is turned off among the light emitting diodes LED1, LED2, and LED3 in the ISDN bus wiring checker 2, and an erroneous wiring in that case.

FIG. 5 is a diagram showing a relationship between a light emitting diode that is turned off among the light emitting diodes LED1, LED2, and LED3 in the ISDN bus wiring checker 2, and an erroneous wiring in that case.

FIG. 6 is a diagram showing a relationship between a light emitting diode that is turned off among the light emitting diodes LED1, LED2, and LED3 in the ISDN bus wiring checker 2, and an incorrect wiring in that case.

FIG. 7 is a diagram showing a conventional ISDN bus wiring checker 3 together with a digital line connection device DSU, an ISDN bus wiring BL1, a communication connector C1, and the like.

FIG. 8 is a diagram showing a conventional ISDN bus wiring checker 4 together with a digital line connection device DSU, an ISDN bus wiring BL1, a communication connector C1, and the like.

[Explanation of symbols]

 1, 2, ISDN bus wiring checker, DSU, digital line connection device for ISDN service, DSUa, DSU connector, C1, C2, C3, communication connector, C1a, C2a, C3a, connector connection portion, BL1, BL2, BL3 .. Bus wiring, L1 first line, L2 second line, L3 third line, L4 fourth line, TA first terminal, TB second terminal, RA third , RB: fourth terminal, 10, 11: voltage applying unit, 10a, 11a: connector, 20, 21: detecting unit, 20a, 21a: connector, B1: first DC power supply, B2: second DC power supply B3 Third DC power supply B4 Fourth DC power supply LED1 First light emitting diode LED2 Second light emitting diode LED3 Third light emitting diode LED4 Fourth light emission Diode, AD: Voltage adjustment circuit.

────────────────────────────────────────────────── ─── Continuation of the front page Examiner Kenji Iwai (56) References JP-A-4-14941 (JP, A) JP-A-7-297898 (JP, A) JP-A 4-20058 (JP, A) Sho-62-239745 (JP, A) Sho-kai 64-5169 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04M 1/24 H04M 3/22-3/36

Claims (6)

(57) [Claims] 1. An ISDN service digital line connection device and a plurality of communication connectors are connected by ISDN bus wiring, and the ISDN bus wiring comprises a first line, a second line, a third line, and a fourth line. After the construction of the above-mentioned ISDN bus wiring or the extension work,
A confirmer for confirming that an N bus wiring is normal, comprising: a first terminal for applying a voltage between a first terminal corresponding to the first line and a second terminal corresponding to the second line. And a second DC power supply for applying a voltage between a third terminal corresponding to the third line and a fourth terminal corresponding to the fourth line, wherein the ISDN A voltage application unit connected to a connector in the service digital line connection device;
A voltage is applied between the first terminal and the second terminal, and a third DC power supply connected in series to the first light emitting unit; and a third DC power supply connected to the third terminal and the fourth terminal. And a fourth DC power supply connected in series to the second light-emitting unit, and a fourth DC power supply that emits light by a voltage applied between the second terminal and the third terminal. And a detector connected to the connector connector of the communication connector. 2. The first DC power supply and the third DC power supply according to claim 1, wherein the first DC power supply and the third DC power supply are connected in series with each other via the first line and the second line which are normally connected. And the second DC power supply and the fourth DC power supply are
An ISDN bus wiring checker, which is connected in series with each other via the third line and the fourth line which are normally connected. 3. The method according to claim 1, wherein at least one of the first, second, third, and fourth DC power supplies includes:
An ISDN bus wiring checker to which a series resistor is connected. 4. The method according to claim 1, wherein at least one of the first, second, third, and fourth DC power supplies includes:
I is characterized in that a diode is connected in series.
SDN bus wiring checker. 5. The ISDN bus wiring checker according to claim 1, wherein a voltage drop element is connected in series with the third light emitting unit. 6. The ISDN bus wiring according to claim 1, further comprising: a fourth light emitting unit connected in parallel and in a reverse direction to the third light emitting unit. Confirmer.