Entrance Current Simulator Device and Pre-Commissioning Method

Abstract

The present invention discloses an input current simulator device and a pre-commissioning method, comprising: a test port, a first switch device, a second switch device, a first variable resistor, a second variable resistor, a matching box, an isolation box, and an ammeter; a first simulation circuit is formed after the first switch device, the first variable resistor, and the ammeter are electrically connected; a second simulation circuit is formed after the second switch device, the second variable resistor, the matching box, the first variable resistor, and the ammeter are electrically connected; a third simulation circuit is formed after the second switch device, the first variable resistor, the isolation box, and the ammeter are electrically connected; when the first switch device and the second switch device are in a first connection state, the first simulation circuit forms a path with the test port; when the first switch device and the second switch device are in a second connection state, the second simulation circuit forms a path with the test port; when the first switch device and the second switch device are in a third connection state, the third simulation circuit forms a path with the test port.

Description

Technical Field

[0001] The present invention relates to the technical field of railway signals, and particularly to an entrance current simulator device. Background Art

[0002] With the continuous increase of the running speed of railway trains in China, people have put forward higher requirements for the safety and comfort of train operation. For a train to run at high speed and smoothly, not only high-reliability trains and high-quality tracks are needed, but also highly reliable and safe signal equipment is required to guide the train operation.

[0003] With the popularization of ZPW-2000 type equipment, the renewal and transformation of codeless equipment are particularly important in the construction of existing lines. It is necessary to ensure the installation quality standard of codeless equipment, the running safety of trains during the equipment installation process, and the smooth commissioning and use of codeless equipment. Among them, the entrance current test is the most crucial step. During the construction test, it is necessary to remove the existing codeless equipment and install and connect the newly installed codeless equipment. The installation process takes a long time, and the entrance current test is not for one section, but for all sections on the entire train route to be replaced simultaneously and then tested. The construction skylight time of existing lines is short, and it is generally very difficult to complete the test. After the existing equipment is restored, it is also necessary to conduct tests. Especially in the busy main line, the effective working time within the skylight time is very short. The workload of the signal interlocking construction line change test on existing lines is very large. The adjustment of the entrance current cannot be carried out synchronously with other interlocking tests and needs to wait for the debugging of other signal equipment to be completed before the test can be carried out, which takes up a lot of line change time. Generally, a station has about 1 hour to complete it. If a failure occurs during the debugging of the entrance current, it will even affect the entire construction line change. Summary of the Invention

[0004] The present application provides an entrance current simulator device for simulating the pre-commissioning of indoor and outdoor entrance currents. The technical solution is as follows:

[0005] In a first aspect, an entrance current simulator device is characterized in that the device includes:

[0006] A test port, a first switch device, a second switch device, a first variable resistor, a second variable resistor, a matching box, an isolation box, a track transformer, and an ammeter;

[0007] After the first switch device, the first variable resistor, and the ammeter are electrically connected, a first simulation circuit is formed for simulating the entrance current circuit during outdoor testing;

[0008] After the second switch device, the second variable resistor, the matching box, the first variable resistor, and the ammeter are electrically connected, a second simulation circuit is formed for simulating the four-wire codeless entrance current circuit during indoor testing;

[0009] After the second switching device, the first variable resistor, the isolation box, and the ammeter are electrically connected, a third analog circuit is formed for simulating the two-wire coded entry current circuit during indoor testing;

[0010] When the first switching device and the second switching device are in the first connection state, the first analog circuit and the test port form a path;

[0011] When the first switching device and the second switching device are in the second connection state, the second analog circuit and the test port form a path;

[0012] When the first switching device and the second switching device are in the third connection state, the third analog circuit and the test port form a path.

[0013] Optionally, the first switching device includes a first selector switch and a second selector switch, and both the first selector switch and the second selector switch include a common contact, a first contact, and a second contact; the second switching device includes a third selector switch and a fourth selector switch, and both the third selector switch and the fourth selector switch include a common contact, a first contact, and a second contact; the first contact of the first selector switch is electrically connected to the common contact of the third selector switch, and the first contact of the second selector switch is electrically connected to the common contact of the fourth selector switch.

[0014] Optionally, the first analog circuit is formed by connecting in series the second contact of the first selector switch, the first variable resistor, and the ammeter, and then electrically connecting to the second contact of the second selector switch. When the common contacts of the first selector switch and the second selector switch are both connected to their respective second contacts, the first switching device and the second switching device are in the first connection state.

[0015] Optionally, the second analog circuit is formed by connecting in series the first contact of the third selector switch, the second variable resistor, the matching box, the first variable resistor, and the ammeter, and then electrically connecting to the first contact of the fourth selector switch. When the common contacts of the first selector switch and the second selector switch are both connected to their respective first contacts, and when the common contacts of the third selector switch and the fourth selector switch are both connected to their respective first contacts, the first switching device and the second switching device are in the second connection state.

[0016] Optionally, the third analog circuit is formed by connecting in series the second contact of the third selector switch, the first variable resistor, the isolation box, and the ammeter, and then electrically connecting to the second contact of the fourth selector switch. When the common contacts of the first selector switch and the second selector switch are both connected to their respective first contacts, and when the common contacts of the third selector switch and the fourth selector switch are both connected to their respective second contacts, the first switching device and the second switching device are in the third connection state.

[0017] Optionally, both the matching box and the isolation box have 4 interfaces, namely the first interface, the second interface, the third interface, and the fourth interface.

[0018] Optionally, the connection mode of the matching box in the second circuit is as follows: the third interface is connected in series with the second variable resistor and the first contact of the third selection switch; after the first interface is connected in series with the first variable resistor and the ammeter, it is then connected to the third interface; the fourth interface is connected to the first contact of the fourth selection switch. The connection mode of the isolation box in the third circuit is as follows: the third interface is connected to the second contact of the fourth selection switch; after the first interface is connected in series with the first variable resistor and the ammeter, it is then connected to the third interface; the fourth interface is connected to the second contact of the fourth selection switch.

[0019] Optionally, the track transformer is connected in series with a fixed resistor and then electrically connected to the non-interface side of the isolation box.

[0020] Optionally, the device further includes two circuit breakers. One end of each of the two circuit breakers is independently and electrically connected to the common contacts of the first selection switch and the second selection switch, and the other end is respectively connected to 2 test ports.

[0021] Optionally, when the track section measured by the device is the receiving end, the fixed resistor is short-circuited and no longer connected in series with the track transformer to the non-interface side of the isolation box; when the track section measured by the device is the sending end, the fixed resistor is normally connected in series with the track transformer to the non-interface side of the isolation box.

[0022] Optionally, the first variable resistor simulates the track resistance, and the second variable resistor simulates the cable line resistance.

[0023] In a second aspect, a method for pre-commissioning the incoming current includes:

[0024] When performing outdoor incoming current testing, connect the common contacts of the first selection switch and the second selection switch to their respective second contacts, turn on the first circuit, adjust the resistance value of the first variable resistor according to the length of the steel rail in the test section, and then perform outdoor incoming current testing.

[0025] When performing indoor four-wire coded current testing, connect the common contacts of the first selection switch and the second selection switch to their respective first contacts, and connect the common contacts of the third selection switch and the fourth selection switch to their respective first contacts. When the second circuit is turned on, adjust the resistance values of the first variable resistor and the second variable resistor according to the length of the steel rail and the length of the cable in the test section respectively, and then perform indoor four-wire coded incoming current testing.

[0026] When performing indoor two-wire coded current testing, connect the common contacts of the first selector switch and the second selector switch to their respective first contacts, and when the common contacts of the third selector switch and the fourth selector switch are both connected to their respective second contacts, the third circuit is turned on. After adjusting the resistance value of the first variable resistor according to the length of the rail in the test section, perform two-wire coded entry current testing indoors.

[0027] The beneficial effects brought by the solution provided in the embodiment of the present application are as follows:

[0028] In the embodiment of the present application, an entry current simulator device is provided. It can simulate the test circuits in indoor and outdoor working sections, perform pre-adjustment of the entry current, reduce the use of Class A skylights, shorten the adjustment time of the entry current during the construction line change process, reduce the workload of operating personnel, improve the efficiency of the blocking line change test, and ensure the safety and punctuality of the signal interlocking transformation construction line change. At the same time, the data reading of the series ammeter is more intuitive. It can simulate four-wire and two-wire systems according to test needs, meet different test requirements, has a wide range of applications, is not restricted by the test site, and can be used indoors and outdoors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The schematic diagrams in the specification forming a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. Among them:

[0030] Figure 1 is the system structure diagram of the entry current simulator device provided in the embodiment of the present application;

[0031] Figure 2 is the schematic structural diagram of 2 switch devices provided in the embodiment of the present application;

[0032] Figure 3 is the schematic diagram of the entry current test circuit during outdoor measurement provided in the embodiment of the present application;

[0033] Figure 4 is the schematic diagram of the four-wire coded entry current test circuit during indoor test provided in the embodiment of the present application;

[0034] Figure 5 is the schematic diagram of the two-wire coded entry current test circuit during indoor test provided in the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application rather than limiting the present application. In fact, those skilled in the art will appreciate that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. Accordingly, it is intended that the present application cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0036] An input current simulator device is provided in an embodiment of the present application. The present invention mainly solves the problems of short adjustment time and large workload during the debugging of the input current.

[0037] As Figure 1 shown,

[0038] An input current simulator device, characterized in that the device comprises:

[0039] A test port, a first switch device, a second switch device, a first variable resistor, a second variable resistor, a matching box, an isolation box, a track transformer, and an ammeter;

[0040] After the first switch device, the first variable resistor, and the ammeter are electrically connected, a first simulation circuit is formed for simulating the input current circuit during outdoor testing;

[0041] After the second switch device, the second variable resistor, the matching box, the first variable resistor, and the ammeter are electrically connected, a second simulation circuit is formed for simulating the four-wire coded input current circuit during indoor testing;

[0042] After the second switch device, the first variable resistor, the isolation box, and the ammeter are electrically connected, a third simulation circuit is formed for simulating the two-wire coded input current circuit during indoor testing;

[0043] When the first switch device and the second switch device are in the first connection state, the first simulation circuit and the test port form a path;

[0044] When the first switch device and the second switch device are in the second connection state, the second simulation circuit and the test port form a path;

[0045] When the first switch device and the second switch device are in the third connection state, the third simulation circuit and the test port form a path.

[0046] Figure 1It is a schematic diagram of the simulator structure. The second contact 12 of the first selection switch 1, the first variable resistor RX1, and the ammeter are connected in series with each other and then electrically connected to the second contact 22 of the second selection switch 2 to form a first simulation circuit; the first contact 31 of the third selection switch 3, the second variable resistor, the matching box HBP-T, the first variable resistor RX1, and the ammeter are connected in series and then electrically connected to the first contact 41 of the fourth selection switch 4 to form a second simulation circuit; the second contact 32 of the third selection switch 3, the first variable resistor RX1, the isolation box WGL-T, and the ammeter are connected in series and then electrically connected to the second contact 42 of the fourth selection switch 4 to form a third simulation circuit.

[0047] The first simulation circuit is used to simulate the incoming current circuit for outdoor testing, the second simulation circuit is used to simulate the incoming current circuit for four-wire code testing indoors, and the third simulation circuit is used to simulate the incoming current circuit for two-wire coding testing indoors. The three simulation circuits are independent of each other and do not affect each other. The corresponding simulation circuit can be selected according to the actual working needs to form a path for incoming current testing.

[0048] It can be understood that each simulation circuit is connected in series with an ammeter. When measuring the incoming current, the current data can be intuitively displayed, and the operation is simple and fast. The three simulation circuits simulate the incoming current testing circuits for different working needs, are integrated on one device, are easy to carry, have a wide application range, meet different needs, improve work efficiency, shorten the testing time, and at the same time reduce the work intensity.

[0049] As Figure 2 shown, Figure 2 It is a schematic diagram of the structures of the first switch device and the second switch device. The first switch device K1 includes the first selection switch 1 and the second selection switch 2. The first selection switch 1 includes a common contact 10, a first contact 11, and a second contact 12. The second selection switch 2 includes a common contact 20, a first contact 21, and a second contact 22; the second switch device K2 includes the third selection switch 3 and the fourth selection switch 4. The third selection switch 3 includes a common contact 30, a first contact 31, and a second contact 32. The fourth selection switch 4 includes a common contact 40, a first contact 41, and a second contact 42; the first contact 11 of the first selection switch 1 is electrically connected to the common contact 30 of the third selection switch 3, and the first contact 21 of the second selection switch 2 is electrically connected to the common contact 40 of the fourth selection switch 4. The common contact of the switch can be connected to different contacts according to the usage needs.

[0050] As Figure 3 shown, Figure 3 It is a schematic diagram of the simulator simulating the incoming current circuit for outdoor testing. Combining Figure 2 and Figure 3, the first analog circuit is formed by electrically connecting the second contact 12 of the first selector switch 1, the first variable resistor RX1, and the ammeter in series and then connecting them to the second contact 22 of the second selector switch 2. When the common contact 10 of the first selector switch 1 and the second contact 12 are connected, and the common contact 20 of the second selector switch 2 and the second contact 22 are connected, the first switching device K1 and the second switching device K2 are in the first connection state, and at this time the first analog circuit is connected to the test port. Among them, the first variable resistor RX1 in the first analog circuit simulates the track resistance value of the test section. When outdoor testing is required, this device is used to select and connect the first analog circuit, and the resistance value of the first variable resistor RX1 is adjusted according to the track length of the section to be tested, and the resistance value of the first variable resistor RX1 is adjusted to be the same as the track resistance value of the test section, and an outdoor test inlet current circuit can be formed. The inlet current can be measured at the outdoor track box using the test port.

[0051] As Figure 4 shown, Figure 4 is a schematic diagram of an analog indoor test four-wire coded entry current circuit. Combining Figure 2 and Figure 4 , when indoor testing of the four-wire coded entry current is required, the common contact 10 of the first selector switch 1 and the first contact 11 are connected, the common contact 20 of the second selector switch 2 and the first contact 21 are connected, and when the common contact 30 of the third selector switch 3 and the first contact 31 are connected, and the common contact 40 of the fourth selector switch 4 and the first contact 41 are connected, the first switching device K1 and the second switching device K2 are in the second connection state, and the second analog circuit is connected to the test port. Among them, the first variable resistor RX1 simulates the track resistance value of the test section, and the second variable resistor RX2 simulates the wire resistance of the cable in the test section. By adjusting the resistance values of the first variable resistor and the second variable resistor according to the length of the test section, an indoor test four-wire coded entry current circuit can be formed, and the indoor four-wire coded entry current can be tested at the indoor distribution board position using the test port.

[0052] As Figure 5 shown, Figure 5 is an analog indoor test two-wire coded entry current circuit. Combining Figure 2 and Figure 5When it is necessary to test the two-wire coded current at the entrance indoors, the common contact 10 and the first contact 11 of the first selector switch 1, and the common contact 20 and the first contact 21 of the second selector switch 2 are connected. And when the common contact 30 and the second contact 32 of the third selector switch 3, and the common contact 40 and the second contact 42 of the fourth selector switch 4 are connected, the first switching device K1 and the second switching device K2 are in the third connection state, and the third analog circuit is connected to the test port. According to the track length of the test section, adjusting the resistance value of the first variable resistor RX1 can form a circuit for testing the two-wire coded current at the entrance indoors. The two-wire coded current at the entrance indoors can be tested at the indoor distribution board position using the test port.

[0053] This application uses variable resistors to simulate the rail resistance value and the wire resistance of the cable, and simulates the test load, which solves the problem of heavy workload in the actual measurement process and resolves the contradiction between the coded test construction and railway transportation. Using electronic components and other equipment to simulate the terminal of the coded circuit equipment, different analog circuits can be used to pre-test the code pattern and the entrance current of the coded equipment in advance. The entrance current simulator can pre-adjust and test the coded pattern and the entrance current before the existing line is blocked and switched, check for wiring errors indoors and outdoors, thoroughly test the indoor and outdoor parts of the coded signal sending circuit in advance, and ensure the accuracy of the test.

[0054] As Figure 1 shown, the matching box HBP-T has 4 interfaces, namely the first interface A1, the second interface A2, the third interface A3, and the fourth interface A4. The isolation box WGL-T has 4 interfaces, namely the first interface I1, the second interface I2, the third interface I3, and the fourth interface I4. The connection of the matching box HBP-T in the second analog circuit is specifically as follows: The third interface A3 is connected in series with the second variable resistor RX2 and the first contact 31 of the third selector switch 3. After the first interface A1 is connected in series with the first variable resistor RX1 and the ammeter, it is then connected to the second interface A2. The fourth interface A4 is connected to the first contact 41 of the fourth selector switch 4. The connection of the isolation box WGL-T in the third circuit is specifically as follows: The third interface I3 is connected to the second contact 42 of the fourth selector switch 4. After the first interface I1 is connected in series with the first variable resistor RX1 and the ammeter, it is then connected to the third interface I3. The fourth interface I4 is connected to the second contact 42 of the fourth selector switch 4.

[0055] It can be understood that the matching box HBP-T is an indoor four-wire coded track circuit device, and its connection in the second analog circuit adopts the wiring method of the four-wire coded track box. The isolation box WGL-T is an indoor two-wire coded track circuit device, and its connection in the third analog circuit adopts the wiring method of the two-wire coded track box.

[0056] The track transformer is connected in series with a fixed resistor and then electrically connected to the non-interface side of the isolation box.

[0057] It can be understood that the non-interface side of the isolation box refers to other directions except for the 4 interface terminals.

[0058] The device also includes two circuit breakers. One end of the two circuit breakers is independently and electrically connected to the common contacts of the first selector switch and the second selector switch respectively, and the other end is connected to 2 test ports respectively.

[0059] As Figure 1 shown, the 2 circuit breakers 3A are connected inside the test ports. The circuit breakers provide overcurrent protection for this simulator to prevent large current from entering the simulator and causing damage to the simulator when the measurement position is incorrect.

[0060] When the track section measured by the device is the receiving end, the fixed resistor is short-circuited and no longer connected in series with the track transformer to the non-interface side of the isolation box; when the track section measured by the device is the sending end, the fixed resistor is normally connected in series with the track transformer to the non-interface side of the isolation box.

[0061] It can be understood that the tested track section is divided into the receiving end and the sending end. Whether the fixed resistor of the third simulation circuit is connected to the simulation circuit depends on whether the track section is the receiving end or the sending end.

[0062] In a second aspect, a method for pre-adjusting the incoming current includes:

[0063] When performing outdoor incoming current testing, connect the common contacts of the first selector switch and the second selector switch to their respective second contacts, and the first circuit is connected. After adjusting the resistance value of the first variable resistor according to the rail length of the test section, perform outdoor incoming current testing;

[0064] When performing indoor four-wire coded current testing, connect the common contacts of the first selector switch and the second selector switch to their respective first contacts, and connect the common contacts of the third selector switch and the fourth selector switch to their respective first contacts. When the second circuit is connected, after adjusting the resistance values of the first variable resistor and the second variable resistor according to the rail length and cable length of the test section respectively, perform indoor four-wire coded incoming current testing;

[0065] When performing indoor two-wire coded current testing, connect the common contacts of the first selector switch and the second selector switch to their respective first contacts, and when the common contacts of the third selector switch and the fourth selector switch are connected to their respective second contacts, the third circuit is connected. After adjusting the resistance value of the first variable resistor according to the rail length of the test section, perform indoor two-wire coded incoming current testing.

[0066] The specific implementation of the above steps of this method can refer to the relevant content of the above input current simulator device, which will not be elaborated here.

[0067] The above are only the preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. An input current simulator device, characterized in that, The device includes: a test port, a first switch device, a second switch device, a first variable resistor, a second variable resistor, a matching box, an isolation box, a track transformer, and an ammeter; After the first switch device, the first variable resistor, and the ammeter are electrically connected, a first analog circuit is formed for simulating the incoming current circuit at the outdoor test entrance; After the second switch device, the second variable resistor, the matching box, the first variable resistor, and the ammeter are electrically connected, a second analog circuit is formed for simulating the incoming current circuit of four-wire coded current at the indoor test entrance; After the second switch device, the first variable resistor, the isolation box, and the ammeter are electrically connected, a third analog circuit is formed for simulating the incoming current circuit of two-wire coded current at the indoor test entrance; When the first switch device and the second switch device are in the first connection state, the first analog circuit and the test port form a path; When the first switch device and the second switch device are in the second connection state, the second analog circuit and the test port form a path; When the first switch device and the second switch device are in the third connection state, the third analog circuit and the test port form a path; The first switch device includes a first selection switch and a second selection switch, and both the first selection switch and the second selection switch include a common contact, a first contact, and a second contact; the second switch device includes a third selection switch and a fourth selection switch, and both the third selection switch and the fourth selection switch include a common contact, a first contact, and a second contact; the first contact of the first selection switch is electrically connected to the common contact of the third selection switch, and the first contact of the second selection switch is electrically connected to the common contact of the fourth selection switch.

2. The inlet current simulator device according to claim 1, characterized in that, The first analog circuit is formed by connecting in series the second contact of the first selection switch, the first variable resistor, and the ammeter and then electrically connecting to the second contact of the second selection switch. When the common contacts of the first selection switch and the second selection switch are both connected to their respective second contacts, the first switch device and the second switch device are in the first connection state.

3. The inlet current simulator device according to claim 1, characterized in that, The second analog circuit is formed by connecting in series the first contact of the third selection switch, the second variable resistor, the matching box, the first variable resistor, and the ammeter and then electrically connecting to the first contact of the fourth selection switch. When the common contacts of the first selection switch and the second selection switch are both connected to their respective first contacts, and when the common contacts of the third selection switch and the fourth selection switch are both connected to their respective first contacts, the first switch device and the second switch device are in the second connection state.

4. The inlet current simulator device according to claim 1, characterized in that The third analog circuit is formed by connecting in series the second contact of the third selection switch, the first variable resistor, the isolation box, and the ammeter, and then electrically connecting to the second contact of the fourth selection switch. When the common contacts of the first selection switch and the second selection switch are both connected to their respective first contacts, and when the common contacts of the third selection switch and the fourth selection switch are both connected to their respective second contacts, the first switching device and the second switching device are in the third connection state.

5. The inlet current simulator device according to claim 1, wherein The matching box and the isolation box each have 4 interfaces, namely the first interface, the second interface, the third interface, and the fourth interface.

6. The inlet current simulator device according to claim 5, characterized in that, The connection mode of the matching box in the second analog circuit is as follows: the third interface is connected in series with the second variable resistor and the first contact of the third selection switch, the first interface is connected in series with the first variable resistor and the ammeter and then connected to the third interface, and the fourth interface is connected to the first contact of the fourth selection switch; the connection mode of the isolation box in the third analog circuit is as follows: the third interface is connected to the second contact of the fourth selection switch, the first interface is connected in series with the first variable resistor and the ammeter and then connected to the third interface, and the fourth interface is connected to the second contact of the fourth selection switch.

7. The inlet current simulator device according to claim 1, wherein The track transformer is connected in series with a fixed resistor and then electrically connected to the non-interface side of the isolation box.

8. The inlet current simulator device according to claim 1, characterized in that, The device further includes two circuit breakers. One ends of the two circuit breakers are independently electrically connected to the common contacts of the first selection switch and the second selection switch respectively, and the other ends are connected to the 2 test ports respectively.

9. The inlet current simulator device according to claim 7, characterized in that, When the track section measured by the device is the receiving end, the fixed resistor is short-circuited and no longer connected in series with the track transformer to the non-interface side of the isolation box; when the track section measured by the device is the sending end, the fixed resistor is normally connected in series with the track transformer to the non-interface side of the isolation box.

10. The entrance current simulator device according to claim 1, characterized in that, The first variable resistor simulates the track resistance, and the second variable resistor simulates the cable line resistance.

11. A method for pre - debugging the input current, characterized in that, The method is applied to the simulator device according to any one of claims 1 to 10, and the method includes: When performing the outdoor entrance current test, connect the common contacts of the first selection switch and the second selection switch to their respective second contacts, turn on the first analog circuit, adjust the resistance value of the first variable resistor according to the length of the rail in the test section, and then perform the outdoor entrance current test. When performing the indoor four-wire coded current test, connect the common contacts of the first selection switch and the second selection switch to their respective first contacts, and connect the common contacts of the third selection switch and the fourth selection switch to their respective first contacts. When the second analog circuit is turned on, adjust the resistance values of the first variable resistor and the second variable resistor according to the length of the rail and the length of the cable in the test section respectively, and then perform the indoor four-wire coded entrance current test. When performing the indoor two-wire coded current test, connect the common contacts of the first selector switch and the common contacts of the second selector switch to their respective first contacts. And when the common contacts of the third selector switch and the common contacts of the fourth selector switch are both connected to their respective second contacts, the third analog circuit is turned on. After adjusting the resistance value of the first variable resistor according to the length of the rail in the test section, perform the indoor two-wire coded entry current test.

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