07_Checking the Electrical Bus Cable

Automation and Drives

Checking the electrical bus cable

PROFIBUS DP

SITRAIN IK-PBS IK-PBSYS YS / BT20 BT200 0 + Diagn Diagnost osticic-Rep Repea eater ter

Page Page 1

Co n t en t s

07/2007 © Siemens AG 2007 2007 - All reightsreserved reightsreserved

Pag e

BT200 BT200 test unit for bus cables cables to RS485 .......... ................ ............ ........... ........... ........... .......... .......... .......... .......... ........... ........... .......... .......... ........... .......... ...... ..

2

Select Select special special mode for extended extended functions functions .......... ............... .......... ........... ............ ........... .......... .......... .......... ........... ............ ............ ............ ........... .......... .....

3

Log kit for BT200 BT200

............ ................. ........... ............ ............ ........... .......... .......... .......... .......... .......... .......... ........... ............ ........... .......... .......... ........... ............ ........... .......... ........... ........

4

Exerci Exercise se 1: Test your your bus cable with with the BT200 BT200 test unit unit ...... ......... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...

5

Exerci Exercise se 1b: Test Test your your bus cable cable with with the the simul simulato atorr and and BT20 BT200 0 test test unit unit ……………… ……………………… ……………. …….

6

Exercise Exercise 2: Branch Branch test test for entering entering all slaves slaves in in a "live list" ........... ................ .......... .......... .......... ........... ........... .......... ........... ............ ......... ...

7

Diagno Diagnosti stic c repeat repeater er

...... ......... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ..... ..

8

Functi Function on of Diagno Diagnosti sticc- Repeat Repeater er ...... ......... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ...... ..... .. Arrangement of the DP master in in the topology ...................................... ........................................................................ ............................................ ..........

9 10

Topology Topology determinati determination on with with STEP STEP7 7

........... ................. ........... ........... ........... .......... .......... .......... .......... ........... ............ ........... .......... .......... ........... ........... .......... .......

11

Location Location of of the the fault fault is is determi determined ned (1) (1)

........... ................ .......... .......... .......... ........... ........... .......... .......... ........... ........... .......... ........... ........... .......... ......... .......... ........

12

Location Location of of the the fault fault is is determi determined ned (2) (2)

........... ................ .......... .......... .......... ........... ........... .......... .......... ........... ........... .......... ........... ........... .......... ......... .......... ........

13

Evaluation Evaluation of the measuremen measurementt results, results, GENERA GENERAL L tab ........... ................ .......... .......... .......... ........... ............ ............ ........... .......... ........... .......... .... Evaluation Evaluation of measurem measurement ent results, results, DP SLAVE SLAVE DIAGNO DIAGNOSTIC STICS S ........... ................ .......... .......... .......... ........... ............ ............ ........... .....

14 15

Evaluation Evaluation of the the measurem measurement ent result results, s, DP1 tab and and DP2 DP2 tab .......... ............... ........... ........... .......... ........... ........... .......... ........... ........... .....

16

Evaluation Evaluation of the measuremen measurementt results, results, DP3 DP3 tab and PG PG tab ........... ................ .......... .......... ........... ........... .......... .......... .......... .......... ........ ...

17

Reading Reading out the diagnostic diagnostic buffer buffer

.......... ................ ............ ........... .......... .......... .......... ........... ........... ........... ............ ........... .......... .......... .......... ........... ............ .......... ....

18

Diagnosis Diagnosis using using the topolo topology gy display display in STEP STEP 7, bus topology topology .......... ............... .......... .......... ........... ........... .......... .......... .......... ........... ........

19

Topology Topology table and Statistics Statistics buffer buffer

........... ................ ........... ............ .......... .......... ........... .......... .......... .......... ........... ........... .......... .......... .......... .......... ........... ......... ...

20

Exercise Exercise 3: Integratin Integrating g the diagnos diagnostic tic repeater repeater into the the system system .......... ............... ........... ........... .......... ........... ........... .......... .......... .......... .....

21

Exercise Exercise 4 : Configuri Configuring ng a diagnostic diagnostic repeater repeater in in STEP7 STEP7 .......... ................ ............ ............ ........... .......... ........... ........... .......... .......... .......... ....... ..

22

Exercise Exercise 5: Diagnosis Diagnosis of bus cable

23

SITRAIN Trainin Training g for Automation and Industrial Solutions

........... ................ ........... ........... .......... .......... .......... ........... ........... .......... ........... ........... .......... .......... .......... .......... ........... .......... ....

Page 1

IK-PBSYS BT200 + Diagnostic-Repeater


BT200 test unit for bus cables to RS485 Testing the PROFIBUS cable: Cable break/shield break Short circuits between cables or cable and shield Fault localization in the event of data cable break/short-circuit Detection of reflections which cause faults Cable replacement Lengths of the installed cables Checking Checking the accessibility of the slaves: List of accessible slaves Specific addressing of individual slaves Checking t he RS 485 interf aces of the masters and slaves: RS 485 drive driver r Supply voltage for cable termination RTS signal Display of the PROFIBUS DP address

SITRAIN IK-PB IK-PBSY SYS S / BT200 BT200 + Diag Diagno nosti stic-R c-Rep epea eater ter

Page Page 2

07/2007 © Siemens AG 2007 2007 - All reightsreserved reightsreserved

Function of the BT 200 The BT 200 offers diagnosis options for PROFIBUS systems by means of the electrical bus cable to RS485. The PROFIBUS cable cable can be tested with the BT200 BT200 test unit during the installation phase. The wiring can even be tested while the stations are connected. Installation errors are detected quickly and easily. The person installing the system does not require specialist PROFIBUS knowledge. The RS 485 interfaces of the PROFIBUS DP stations can be tested even before the system is commissioned. The slaves which can be reached on the installed bus can be listed without a master on the PROFIBUS DP. In this way, the operating capability capability of individual bus segments can be tested beforehand which reduces commissioning times. With the help of the optional log kit the individual tests can be stored in the BT200 and transmitted to a PC. The test results can then be printed out in the form of a report. In this way, the acceptance log can be drawn up simply and quickly.

SITRAIN Trainin Training g for Automation and Industrial Solutions

Page 2



Select special mode for extended functions Menue for standard and special mode

Press the OK AND ESC keys simultaneously ===> SPECIAL MODE activ ated

+

SITRAIN IK-PBSYS / BT200 + Diagnostic-Repeater

Special mode

Page 3

07/2007 © Siemens AG 2007 - All reightsreserved

Press the ESC and OK keys simultaneously to switch from normal mode to special mode. The following functions are available in special mode: • Wiring test (see normal mode). • Station test • Swapped cores • Short-circuit • Broken wire or shield • None or more than two terminating resistors • Station test (RS485 test) • Branch test • Distance measurement • Reflection test • Service menu

Menu i tems

Menu items are selected with the cursor and activated with theOK key. The ESC key can be used to cancel the current function or to return to the higher-level menu item.

Operation

The BT 200 is menu-driven using the input keys of the membrane keypad.

Cursor

The current position of the cursor on the display is indicated by a flashing arrow which also indicates the function being executed.

SITRAIN Training for Automation and Industrial Solutions

Page 3



Log kit for BT200


General

Page 4


In recording mode, implemented tests are logged in the BT200 and can then be transferred via a serial (COM) interface to a PC with logging software. The required logging kit comprises the software and connecting cable for the PC and can be ordered using the order number 6ES7 193-8MA00-0AA0.


Page 4



Exercise 1: Test your bus cable with the BT200 test unit g o.k . Cabelin ling OK (2R)


Page 5


Task description:

Test the bus cable which you will be using for the next few exercises.

Procedure:

The wiring test for a bus segment is performed between the BT 200 and test plug. •

No stations may be connected to the bus cable.

•

The test plug must be connected to one end of the bus cable which is to be tested

•

The terminating resistor at the end of the test plug must be activated

•

The terminating resistor on the connection point of the BT200 must be activated

1. Construct the test setup as described above. 2. Press the button to switch on the BT200. 2. Press the "TEST" button for a short time. The message “Please wait..." is displayed. 3. As a result of the test, a message is displayed which could be as follows : " Wiring OK (1R) OK.


Page 5



Exercise 1b: Test your bus cable with the simulator and BT200 test unit B -> Sh A -> B A -> Sh A -> A B -> B Signal „0“ 3-5 Signal „0“ 8-6


Page 6


Task description:

Test the bus cable with the simulator and the BT200.

Procedure:

1. Connect the „simulator “ between the BT200 and the test plug. 2. Test the different switches on the simulator and check the result with the BT200.


Page 6



Exercise 2: Branch test for entering all slaves in a "live list" ON Off

Master not connected to bus

ON

• "Live list" also over repeaters and opt. paths • Subsystems can be tested first for proper functioning of the bus; no master is required


Branch test

Page 7


In this way, the availability of all slaves connected to PROFIBUS can be tested or an individual slave can be addressed. The branch test can also be performed over repeaters or fiber-optic cables.

Procedure

• • • • • • • • •

Test results

Remove all masters from the bus, e.g. PGs, OPs, CPs (see Figure above). All slaves must be switched on and supplied with power. Connect BT 200 to the bus as shown in the figure above, for example Select special mode by simultaneously pressing theESC and OK keys. Now use the cursor key "“ to point to the menu item "Branch test“, with the flashing menu arrow next to this text. Now select it with the " OK key". The text "Branch test" is displayed. Then press the "TEST key" To check which slaves are connected to the branch, use the cursor keys of the BT200 to enter "000" as the slave address and confirm with the OK key. "Please wait" is displayed After the search is complete, the slave numbers found are output on the display separated by commas. For the total branch test, each accessible slave is listed in a list of accessible stations (LIVE LIST).


Page 7



Diagnostic repeater S7-CPU

STEP7 COM PROFIBUS Segment 1 Start determining of topology

Diagnostic distance to slave

distance to disturbance

Segment 2


Introduction

Segment 3

Page 8


Under normal operating conditions, the bus cables are also subjected to external forces that can cause damage. In particular, in the case of exceptional stress, e.g. trailing cables or strong vibrations, frequent inspection of the cables is recommended to reduce failures to a minimum.

Diagnostic repeater The diagnostic repeater is available for line diagnostics during normal system operation. It is integrated as an RS 485 repeater in the PROFIBUS DP network and also features powerful functions for line diagnostics. The diagnostic repeater detects the following cable faults: • Wire break A or B • Short-circuit between signal lines and the shield • Missing bus terminating resistor The diagnostic repeater is configured as a standard slave in STEP 7, with COM PROFIBUS or using the GSD file. Design

• • • • • • •

Connection of 3 segments, of which diagnosis is possible for 2 Connection of up to 62 nodes (31 per diagnosable segment) Connection of up to 9 diagnostic repeaters in series Mounting on S7-300 rail or standard rail LEDs for indication of 24 V DC, bus activity and line faults for each segment Terminal block for external 24 V DC supply voltage 9-pin Sub D socket for PG connection, electrically isolated


Page 8



Function of the Diagnostic- Repeater

PG interface CPU 2

Start Topology determination

STEP 7 > V5.1 SP2

3 Segment 1 Slave distance

4

5

12

17

Segment 2

Segment 3


Area of ap plicati on

9

Page 9


The diagnostics repeater is a repeater that can monitor up to two segments of an RS 485 PROFIBUS network (copper line) during operation and signal line faults in a diagnostics message to the DP master. The fault location and cause can then be displayed in plain text by means of an HMI device. The line diagnostics during operation by the diagnostics repeater permits early detection and locating of line faults.

Prerequisites

Line diagnostics

•

Line diagnostics are possible for nodes that are connected to PROFIBUS segments DP2 and DP3.

•

To implement a diagnostic repeater, you will need a PG/PC and STEP 7 V5.1 Service Pack 2 or higher or COM PROFIBUS V5.1 Service Pack 2.

•

To activate topology determination from the user program, an S7 CPU/CP will be required that supports the integrated system function SFC 103 "DP_TOPOL" (e.g. integrated DP interfaces of S7-400 CPUs FW 3.1 and higher).

Line diagnostics are performed in two steps: Step 1: Toplogy determination The diagnostic repeater determines the PROFIBUS addresses and distances to the nodes and creates a topology table. Step 2:


Fault localization The diagnostic repeater checks the cables during normal operation of the bus. It determines the distance to the fault location, determines the cause of the fault and issues a diagnostic alarm with a relative specification of the fault location.

Page 9



Arrangement of the DP master in the topology Ar ran gement wi th one segment ( DP2)

DP1: non diagonostics-capable segment

DP2: diagonostics-capable segment

Ar ran gem ent wi th two segments ( DP2 and DP3)


Page 10


Prerequisities for determining the topology A DP master is required for determining the topology that initiates the necessary measurements and that is able to provide its diagnostic information over the diagnostic repeater. Arrangement o f t he DP mas ter It is usually recommended that the DP master is connected to the A1/B1 connection of segment DP1 of a diagnostic repeater. Ar rang ement wit h one seg ment (DP2) When only one segment with diagnostics capability is required, segment DP2 of the diagnostic repeater must be used. If a bus cable is not connected to segment DP3, the SEGMENT DP3 rotary selector switch must be set to OFF. Arrangement w it h two segments (DP2 and DP3) If a bus cable is connected to segment DP3, the SEGMENT DP3 rotary switch must be set to ON. If an outgoing bus cable is not connected to the A1‘/B1‘ connections of segment DP1, the TERMINATOR DP1 rotary switch must be set to ON. The terminating resistor for segment DP1 is therefore connected and the A1‘/B1‘ connections are deactivated. Determining th e topology w ith STEP 7 •

In SIMATIC Manager, select the PROFIBUS network where the diagnostics repeater with the connected PG/PC is located and select the menu command Target system - PROFIBUS – Prepare line diagnostics.

•

In the dialog box that is then displayed, select the button “Start measurement“.


Page 10



Topology determination with STEP7

Example user programs

CALL "DP_TOPOL" SFC103 Calling topology determination REQ :=M2.0 Starting topology determination (bool) R :=M2.1 =1: Interrupt topology determination (bool) DP_ID :=1 ID of the DP master system whose topology has to be determined (int) RET_VAL :=MW110 Return value for task status (int) BUSY :=M112.0 =1 Topology determination is not yet completed. DPR :=MB124 PROFIBUS address of the diagnostic repeater reporting the fault (byte) DPRI :=MB125 Measuring segment of the diagnostic repeater reporting the fault (byte)


Page 11


Determin ing t he topo logy wit h SFC 103 "DP_TOPOL" The topology can also be determined using an S7 CPU that supports the integral system function SFC 103 "DP_TOPOL". You can use SFC 103 "DP_TOPOL" to start determining the topology for a selected DP master system. The SFC 103 call addresses all the diagnostic repeaters on a DP master system. Duration of topology determination The duration of the topology determination procedure is dependent on the structure of your system and the transmission rate. Topology determination will be interrupted if the duration exceeds the limits specified in the table. Transmission rate

Limit values

12 MB

5 min.

6 MB

5 min.

3 MB

5 min.

1.5 MB

8 min.

500 KB

12 min.


Page 11



Location of the fault is determined (1)

Segment OK Segment disturbed Segment OFF No information for the Segment


Page 12


Determining the fault l ocation during operation The diagnostic repeater signals the event "Fault location determined" during normal operation as a diagnostic alarm to the CPU of the DP master. You can display detailed information about the diagnostic event that has occurred in the module information dialog box for the diagnostic repeater. The fault location is shown pictorially in the dialog box with additional information, e.g. about the cause of the fault (if it can be determined by the diagnostic repeater).


Page 12



Location of the fault is determined (2)


Page 13


Example of a pictorial display in the " Module information" d ialog box If all the segments to which the diagnostic repeater is connected function correctly, the corresponding tabs in the "Module information" dialog box are as follows:

The "DP2" tab could show the d isturbance in the following view: The Diagnostic Repeater is assigned to PROFIBUS address 4, the error is located between the partners assigned to the PROFIBUS addresses 16 and 21. In addition, the view shows the distance to the neighboring DP Slaves.

In the figure below you can find an example of a simplified detailed presentation of the arrangement illustrated above.


Page 13



Evaluation of the measurement results, GENERAL tab


Page 14


General

This tab sheet contains general data concerning the module: Description, system identification, rack, slot and module width

Address :

The address displayed is the start address of the useful data area: For modules without a useful data area, it corresponds to the diagnostic address.

System behavior :

When the module is a CPU with multi-computing capability, this information is shown here.

Version

The order number and version of the selected module is indicated here. This display comprises several components that vary in accordance with the module type, for example, separate entries for the hardware and firmware of the module.

Status

The existing status information is indicated here Status of the module from the viewpoint of the CPU, e.g.: • Module found and OK. • Module faulty. • Module configured but not found. • Error LEDs • Differences detected between configured and inserted modules. The Order numbers for the required type and actual type are displayed if they can be determined. • For DP slaves, the status of lower-level modules can be displayed here. The scope of information displayed varies in accordance with the selected module and as to whether the function was called from the window "Accessible nodes" or from a project window.

Identification

Name of the PLC, name of the CPU, system identification


Page 14



Evaluation of measurement results, DP SLAVE DIAGNOSTICS

Diagnosis in Hexadezimal Format


Page 15


" DP slave diagnostics" This tab sheet contains slave diagnostic data that is presented in accordance with EN 50170, Part 3, PROFIBUS. Standard diagnosis o f s lave General diagnostic information of the slave: The information refers to correct startup or failure of the slave. Errors that are displayed here are of the type "Slave cannot be addressed", configuration errors or parameter assignment errors. Device-specific diagnostic text of the slave: The diagnostic texts displayed are obtained device-specifically using the GSD file (device master file). If the diagnostic message is not stored in the GSD file, the diagnosis cannot be displayed as plain text. The channel information is only visible when you open the station online in the STEP 7 project. When you open the station online without reference to a project (via accessible nodes), there is no assignment to a GSD file and the channel information is not visible. Channel-specific diagnosis Display of channel-specific diagnostic texts for configured modules of the DP slave: For each diagnostic message, the activating channel is specified. A channel is uniquely identified by the slot location of the module and the channel number. Device-specific diagnostic texts are obtained using the GSD file. If the diagnostic message is not stored in the GSD file, the diagnosis cannot be displayed as plain text. "Hex. format" button When you click this button, the complete diagnostic message frame is output in hexadecimal format.


Page 15



Evaluation of the measurement results, DP1 tab and DP2 tab

Segment DP1 is OK

Graphical display of fault location: Display of possible cause of fault:

Further details about the displayed fault


DP1 tab

Page 16


A tab sheet is assigned for each connection of a diagnostic repeater to a segment a fault in a segment is indicated by a fault symbol. If a fault is detected or if the interface for this segment is switched off (segment is deactivated), an appropriate message is displayed in the tab. If a fault is detected, the following fields will be displayed:

Error location Error Remedy

In the "Error location" field, the location of the fault is displayed graphically provided that the diagnostic repeater can determine the location. The fault is explained in plain text in the "Error" field. In the "Remedy" field you will find measures for rectifying the fault. If the "Details" button is activated, you can use it to display further details of the fault.


Page 16



Evaluation of the measurement results, DP3 tab and PG tab



Page 17

Page 17




Reading out the diagnostic buffer


Diagnostic buffer

Page 18


The diagnostic repeater contains one diagnostic buffer for each of segments DP1, DP2, DP3 and the PG interface in which the last 10 events are saved. The buffer contains the time, date and a brief description of the events. Incoming error events are indicated with "I" and outgoing error events are indicated with "O". The diagnostic buffers can be printed out. They can be exported as CSV files and then read into Microsoft Excel and evaluated. The diagnostic buffers can also be read out from the user program, whereby the function block SFC59“RD_REC“ must be used (see online help).

Procedure

1. Mark the DP master system whose data you want to read. 2. Start the function using the menu item Options > Diagnostic buffer .


Page 18



Diagnosis using the topology display in STEP 7, bus topology

Diagnostic - Repeater


Page 19


Prerequisite

To ensure that the distances specified in diagnostic messages are correct, the topology must be determined again following every change in structure of the bus!

Requirements

The diagnostics repeaters must support the function “Display PROFIBUS network topology”. The PROFIBUS network must be set up according to the rules in the diagnostics repeater manual so that the distance data can be determined correctly. If diagnostics repeaters are cascaded, for example, they must only be connected to a higher-level diagnostics repeater via the DP1 interface. For the function “Prepare line diagnostics”, the programming device (PG) and the diagnostics repeaters must be connected to the same PROFIBUS. “Prepare line diagnostics” is also possible if no project is open. For the function “Display PROFIBUS network topology”, the PROFIBUS network with the diagnostics repeaters can also be connected to the programming device via a “Data record router” (e.g. CP 443-5 Ext V3.2). The programming device must be assigned in the STEP 7 project (menu command Target system – Assign PG/PC, in NETPRO use for the object “PG/PC”). In order to be able to display the network topology via a routed diagnostics repeater, the corresponding project must be opened and the corresponding PROFIBUS subnetwork must be selected.

Procedure

1. In STEP 7, mark the DP master system whose data you want to read. 2. Start the function using the menu commandView > Display > Al l nodes/Onl y DR wit h nodes/Onl y DRs.


Page 19



Topology table and Statistics buffer

There are too many line faults. Operation of the segment is no longer possible Line faults have been detected. Operation of the segment is still possible. Nodes may, however, fail as a result.

A few line faults have been detected. Operation of the segment is optimal. The severity of faults can also be assessed on the basis of the color coding.


Page 20


Topology table

The topology table contains the following information: • PROFIBUS address of the node. • Designation of the node, if it can be determined. • Address of the associated diagnostic repeater to whose measuring segment the node is connected. • Distance with reference to the associated diagnostic repeater • Segment of the diagnostic repeater to which the node is connected. • Time when topology was last determined. The topology table can be printed out. It can be exported as a CSV file and then read into Microsoft Excel and evaluated. It can also be read out from the user program, whereby the function block SFC59“RD_REC“ must be used.

Procedure

1. Mark the DP master system whose data you want to read. 2. Start the function using the menu item View > Topology table.

Statistic s buffer

The diagnostic repeater contains one statistics buffer each for segments DP2 and DP3 in which information about the reflection error rate and message frame error rate can be saved. Reflection errors occur, for example when the signal is reflected through a faulty or defective line. Message fr ame errors are detected when message frames with, fo r example, parity errors occur. Parity errors can be caused, for example, by a defective node. The values are displayed for a period of 60 seconds starting from the time when the dialog box was opened. Internally, further values are saved over the displayed period. The statistics buffers can be printed out. They can be exported as CSV files and then read into Microsoft Excel and evaluated. The statistics buffers can also be read out from the user program.

Procedure

1. In the topology display, mark the diagnostic repeater whose data you want to read out. 2. Start the function using the menu item Options > Statisti cs.


Page 20



Exercise 3: Integrating the diagnostic repeater into the system


Page 21


Task:

The diagnostic repeater must be integrated into your existing system line faults must be provoked and diagnosed using the diagnostic repeater.

Procedure:

1. Modify your system as shown in the diagram above. 2. Code the diagnostics repeater as follows: • DP3 switch in the ON position • DP2 switch in the ON position • Set the DP address switch (DIP switch) to address “9“ • DP address switch, set the identifier with DR to OFF for no repeater function


Page 21



Exercise 4 : Configuring a diagnostic repeater in STEP7 Diagnostic - Repeater

Properties


Task

Page 22


The diagnostics repeater is to be configured for the master system with the PROFIBUS address 9 as further DP slave.

Implementation 1. Open the hardware configuration on your training station 2. Drag the object Diagnosti cs Repeater from the hardware catalog under PROFIBUS DP - Network Components to the master system 3. Assign the bus address 9 to this DP slave 4. Generate new system data blocks 5. Download the changed configuration onto the master CPU The master system should “ramp up“ without errors just like before 6. Connect the PG to the PG socket on the front of the diagnostics repeater using the connecting cable of the diagnostics repeater 7. In SIMATIC Manager, select the subnetwork PROFIBUS(1) and select the menu command Target system - PROFIBUS – Prepare line diagnostics... 8. In the next window, start topology determination by clicking on the button “Restart”


Page 22



Exercise 5: Diagnosis of bus cable


Page 23


Implementation 1. Generate a bus fault, e.g. by removing a supply line in a bus connector. 2. Is the information about cable lengths consistent with the cable lengths in the actual network?


Page 23


07_Checking the Electrical Bus Cable

Recommend Documents