Multi-branch cable 24-hour theft prevention circuit and method without additional communication mode

Abstract

The application discloses a kind of multi-branch cable 24-hour theft prevention circuit and method without additional communication mode, and the theft prevention circuit includes: isolated power supply P1, one or more induction circuits, and one or more detection circuits, the isolated power supply P1 is connected with multiple induction circuits and multiple detection circuits, each induction circuit matches a detection circuit to form a loop cable detection circuit;Each induction circuit includes first transformer T1, second transformer T2, rectifier bridge D2, relay and switch K1;Each detection circuit includes operational amplifier and optocoupler U4.The application does not need to rely on any additional communication mode, in the same scheme, the current threshold detection of street lamp line when street lamp cable is live and the cable on-off detection under no live state are realized, so that multi-branch cable 24-hour theft prevention without additional communication mode is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cable theft prevention, and particularly relates to a 24-hour theft prevention circuit and method for multi-branch cables without external communication mode. BACKGROUND

[0002] In recent years, the realization of timely and accurate alarm for street lamp cable theft has been a technical difficulty in the industry. Currently, the technologies for cable theft prevention mainly include the following three types.

[0003] 1. Power line carrier communication monitoring theft prevention method; the power line carrier communication method uses signal transmission means to load a detection carrier signal on the cable in the detection range. The alarm of the monitoring center is connected with the carrier signal on the monitored cable. Once the cable is broken, causing the signal transmission to be interrupted, the alarm cannot receive the signal and will automatically alarm, playing a warning role. The power line carrier communication method is the most widely used theft prevention method at present. Because it transmits the carrier signal on the monitored cable, it does not require additional lines, and therefore has the advantages of simple installation, concealed investigation, and wide monitoring range (more than several kilometers). However, the power line carrier communication method still has the following problems to be solved: (1) the power distribution system transformer has a blocking effect on the power line carrier communication information; (2) the three-phase power system in the circuit has a signal loss of 10-20 dB, and when the communication distance is relatively short, the carrier signal can only be transmitted on a single-phase line; (3) the power line has its own pulse interference. The frequency of alternating current is 50 Hz, and there are two wave peaks in a single cycle of the sine curve, which will generate a secondary pulse interference, i.e. 100 Hz pulse interference, which is an inherent property of the power line; (4) different signal coupling methods correspond to different power line carrier communication signal losses; (5) the power line can cause data signal distortion.

[0004] 2. Installing communication equipment at the end of the lamp pole to implement alarm; communication equipment is installed at the end of the lamp pole, which is powered by the street lamp line and communicates with the main station through wireless (radio) or wired telephone line. The alarm mode also has active and passive types. The active type needs to install a battery, and once the end of the line is powered off, it is considered that the cable is stolen, and the main station is alarmed. The passive type is continuously patrolled by the main station, and when multiple tests are not connected (because the powered-off equipment cannot work), it is considered that the cable is stolen. This method is relatively reliable, i.e. the false alarm rate is relatively low, and it can accurately locate according to the coded address, but it also has certain limitations: (1) it can only alarm when the line is powered (it cannot be 24 hours all day); (2) the initial investment and installation difficulty are relatively large, which includes: the end of the lamp pole must have a radio or telephone line access, antenna installation, lightning protection measures, etc.

[0005] 3. Current detection type monitoring anti-theft method; this method detects whether there is a transmission current in the cable loop to determine the integrity of the cable system. That is, when the cable is working normally, the detection system has no response; when there is no current transmission in the cable, the detection system will start the alarm system. This current detection system cannot be used for cable anti-theft systems with voltage and no current, such as subway tunnels or highway tunnel blower power cables. In addition, this system can only alarm when all branch cables of the circuit system are cut off (because the total current of the cable loop is zero when all cable branches are cut off), so the current detection type monitoring system has the risk of "no alarm".

[0006] Therefore, how to realize a 24-hour monitoring of cable theft without additional communication methods is one of the technical problems to be solved by those skilled in the art. SUMMARY

[0007] The main purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and the present application provides a multi-branch cable 24-hour anti-theft circuit and method without additional communication methods, which can realize 24-hour cable anti-theft monitoring without relying on additional communication methods.

[0008] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0009] In a first aspect, the present application provides a multi-branch cable 24-hour anti-theft circuit without additional communication methods, comprising an isolation power supply P1, one or more sensing circuits, and one or more detection circuits, the isolation power supply P1 is connected with the plurality of sensing circuits and the plurality of detection circuits, each sensing circuit matches a detection circuit to form a loop cable detection circuit;

[0010] Each sensing circuit comprises a first transformer T1, a second transformer T2, a rectifier bridge D2, a relay and a switch K1, the primary winding of the second transformer T2 is connected between detection points L and N, the secondary winding of the second transformer T2 is connected with the relay after being rectified by the rectifier bridge D2, the switch K1 is opened when the relay is powered on, and the switch K1 is closed when the relay is powered off, one end of the switch K1 is connected with the primary winding of the first transformer T1, and the other end of the switch K1 is connected with a port I, the port I is connected with the detection circuit when the line is not powered; a port Rd1 is arranged between the rectifier bridge D2 and the relay, and the port Rd1 is connected with the detection circuit when the line is powered;

[0011] Each detection circuit comprises an operational amplifier and a photocoupler U4, the non-inverting input of the operational amplifier is connected to the port Rd1 through a diode D6, a resistor R5 is arranged between the non-inverting input of the operational amplifier and the diode D6, the resistor R5 is connected to the port I, the inverting input of the operational amplifier is connected to the isolation power supply P1, the output of the operational amplifier is connected to the cathode of the photocoupler U4, the anode of the photocoupler U4 is connected to a light emitting diode D5, the emitter of the photocoupler U4 is grounded, and the collector of the photocoupler U4 is connected to a cable through a resistor R6.

[0012] As a preferred technical solution, the detection points L and N of the second transformer T2 are connected to the live wire and the zero line respectively, and the end R2 of the street lamp line is connected between the detection points L and N as an inductor.

[0013] As a preferred technical solution, the input and output of the rectifier bridge D2 are provided with a capacitor C2; the relay is connected in parallel with a diode D1, and the diode D1 and the relay are connected at one end of a capacitor C1 and a resistor R1 connected in parallel, and the other end is grounded.

[0014] As a preferred technical solution, the resistor R5 and the port I are provided with a resistor R4 and a capacitor C3 connected in parallel and grounded.

[0015] As a preferred technical solution, the fourth interface of the isolation power supply P1 and the inverting input of the operational amplifier are provided with a resistor R9, the third interface of the isolation power supply P1 and the inverting input of the operational amplifier are provided with a resistor R11, and the capacitor C4, the capacitor C5 and the capacitor C6 connected in parallel are arranged between the resistor R9 and the resistor R11; the fourth interface of the isolation power supply P1 and the resistor R9 are provided with a resistor R7, and the resistor R7 is connected to the anode of a light emitting diode D4.

[0016] As a preferred technical solution, the fourth interface of the isolation power supply P1 and the resistor R7 are provided with a diode D3, and the other end of the diode D3 is connected to the detection point N of the second transformer T2.

[0017] As a preferred technical solution, the induction circuit and the detection circuit are both 4-way.

[0018] As a preferred technical solution, the operational amplifier is selected from LM258; and the photocoupler U4 is selected from PC817.

[0019] In a second aspect, the application provides a detection method of a 24-hour anti-theft circuit of a multi-branch cable without an additional communication mode, in a line light-on state, i.e. the street lamp line is normally working with electricity, whether the line is stolen or not is determined by detecting a current threshold value, when the detected current is lower than the set threshold value, the terminal host actively uploads an undercurrent alarm information, which is a current threshold value determination mode, and specifically:

[0020] When the line is electrified, there is 220V voltage between the detection point L and N, the second transformer T2 works to supply the relay through the rectifier bridge D2, the contact is attracted to the normally open end, the switch K1 is disconnected with the port I, the first transformer T1 is disconnected with the same phase input end of the operational amplifier, at the same time, the second transformer T2 is rectified through the rectifier bridge D2, filtered through the port Rd1, the resistance R3 and the diode D6 to supply the same phase input end of the operational amplifier, the output end of the operational amplifier outputs high level, through the resistance R8 to the light emitting diode inside the optocoupler U4, the diode D5 is cut off, the optocoupler U4 does not emit light, the amplification end is low level and is transmitted to the host computer, at this time, the current detection threshold value of the path is used to judge whether the current is insufficient to judge whether the cable is disconnected, if the current is lower than the threshold value, the host computer displays the undercurrent / disconnection alarm.

[0021] In the third aspect, the application provides a detection method of the 24-hour anti-theft circuit of the multi-branch cable without additional communication mode, in the state without lighting of the line, whether the closed loop circuit of the line is disconnected is detected, specifically:

[0022] When the line is not electrified, there is a inductor R2 with a DC resistance of 250V and less than 200Ω as the end terminal connected to the zero line and the live line of the street lamp line, which forms a closed loop circuit with the induction circuit, because the line is not electrified, there is no 220V voltage between the detection point L and N, the relay is released, the normally closed switch K1 is connected to the first transformer T1 through the port I, the resistance R5 and the same phase input end of the operational amplifier, the fourth interface of the isolation power supply P1 supplies 9V DC to the zero line N, then to the detection end R2 through the zero line, to the same phase input end of the operational amplifier through the live line L, the first transformer T1, the switch K1 and the resistance R5, the output end of the operational amplifier outputs high level 12V, through the resistance R8 to the light emitting diode inside the optocoupler U4, the diode D5 is cut off, the optocoupler U4 does not emit light, the amplification end is low level and is transmitted to the host computer; in the state without lighting, when the line is stolen and cut, the live line or the zero line of the line is disconnected, the fourth interface of the isolation power supply P1 cannot supply 9V to the third interface of the operational amplifier, the first interface of the operational amplifier outputs low level, the optocoupler U4 emits light and the diode D5 is turned on to emit light, the amplification end of the optocoupler has high level, that is, the cable disconnection signal is continuously transmitted to the host computer to display the disconnection alarm.

[0023] Compared with the prior art, the application has the following advantages and beneficial effects:

[0024] (1) The invention relates to a kind of multi-branch cable 24-hour theft prevention circuit without relying on additional communication mode, which can well solve the above-mentioned method, especially solve the above-mentioned current detection type monitoring theft prevention method has the deficiency of branch cable and voltage without current cannot timely alarm, at the same time, it is necessary to solve the deficiency of relying on additional communication mode, and additional communication exists many environmental interference factors, need to maintain additional communication equipment in time, without relying on any additional communication mode, realize the on-line detection theft prevention of street lamp cable with electricity and without electricity in the same scheme.

[0025] (2) The invention does not need multiple technologies overlap, in the same scheme, each theft prevention module unit can simultaneously realize the cable theft prevention of 4 branches, and can be configured in 4 branches as a unit, realize the 24-hour theft prevention of any branch number cable. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 is the structure diagram of the invention embodiment of multi-branch cable 24-hour theft prevention circuit without additional communication mode under the state of electricity.

[0028] Figure 2 is the structure diagram of the invention embodiment of multi-branch cable 24-hour theft prevention circuit without additional communication mode under the state of electricity. DETAILED DESCRIPTION

[0029] In order to make the person in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] In the present application, the "additional communication mode" refers to a wired or wireless communication measure, such as power line carrier communication, wireless signal transceiver, etc., which is not required to be additionally loaded at the two ends of the cable to be detected for realizing the anti-theft detection of the cable. The present application is to judge the integrity of the cable system by detecting whether the loop in the online detection cable loop is closed or whether the current is lower than the threshold value, that is, when the cable is normally working, the cable anti-theft circuit has no response; when the closed loop of the cable to be detected is disconnected or the current is lower than the threshold value, the anti-theft circuit of the present application will start the alarm to remind.

[0031] Please refer to Figure 1 and Figure 2 The 24-hour anti-theft circuit of the multi-branch cable without additional communication mode of the embodiment comprises an isolation power supply P1, a plurality of sensing circuits and a plurality of detection circuits, the isolation power supply P1 is connected with the plurality of sensing circuits and the plurality of detection circuits, each sensing circuit matches a detection circuit to form a loop cable detection circuit, and the cable detection circuit is used to detect whether the cable is disconnected in the live and unlive states.

[0032] Further, each sensing circuit comprises a first transformer T1, a second transformer T2, a rectifier bridge D2, a relay and a switch K1, the primary coil of the second transformer T2 is connected with the detection points L and N, the secondary coil of the second transformer T2 is connected with the relay after being rectified by the rectifier bridge D2, the switch K1 is opened when the relay is powered on, the switch K1 is closed when the relay is powered off, one end of the switch K1 is connected with the primary coil of the first transformer T1, the other end of the switch K1 is connected with a port I, the port I is connected with the detection circuit when the line is unlive; a port Rd1 is arranged between the rectifier bridge D2 and the relay, and the port Rd1 is connected with the detection circuit when the line is live.

[0033] It can be understood that the detection points L and N of the second transformer T2 are respectively connected with the live wire and the zero line, and the end R2 of the street lamp line is connected between the detection points L and N as an inductor when it is live and as a resistor when it is unlive.

[0034] Further, a capacitor C2 is arranged between the input end and the output end of the rectifier bridge D2; the relay is connected in parallel with a diode D1, a capacitor C1 and a resistor R1 are connected in parallel, one end of which is connected with the diode D1 and the relay, and the other end is grounded; a resistor R4 and a capacitor C3 are arranged between the resistor R5 and the port I, and the resistor R4 and the capacitor C3 are connected in parallel and grounded.

[0035] Further, each detection circuit comprises an operational amplifier and a photo-coupler U4, the non-inverting input of the operational amplifier is connected to the port Rd1 through a diode D6, a resistor R5 is arranged between the non-inverting input of the operational amplifier and the diode D6, the resistor R5 is connected to the port I, the inverting input of the operational amplifier is connected to the isolation power supply P1, the output of the operational amplifier is connected to the cathode of the photo-coupler U4, the anode of the photo-coupler U4 is connected to a light emitting diode D5, the emitter of the photo-coupler U4 is grounded, and the collector of the photo-coupler U4 is connected to the cable through a resistor R6.

[0036] Further, a resistor R9 is arranged between the fourth interface of the isolation power supply P1 and the inverting input of the operational amplifier, a resistor R11 is arranged between the third interface of the isolation power supply P1 and the inverting input of the operational amplifier, and a capacitor C4, a capacitor C5 and a capacitor C6 are connected in parallel between the resistor R9 and the resistor R11; a resistor R7 is arranged between the fourth interface of the isolation power supply P1 and the resistor R9, and the resistor R7 is connected to the anode of a light emitting diode D4.

[0037] Further, a diode D3 is arranged between the fourth interface of the isolation power supply P1 and the resistor R7, and the other end of the diode D3 is connected to the detection point N of the second transformer T2.

[0038] In the embodiment, the induction circuit and the detection circuit can be configured as 4 paths, and can be configured in units of 4 branches to realize 24-hour anti-theft of cables of any branch number.

[0039] The following will be described in combination with Figure 1 and Figure 2 , the operational amplifier is selected as LM258, the photo-coupler U4 is selected as PC817, and the corresponding circuit structure and detection method in the charged state and the uncharged state are specifically described. It can be understood that LM258 and PC817 are one type of the present application, and other operational amplifiers and photo-couplers capable of realizing the technical scheme of the present application are within the protection scope of the present patent.

[0040] Please refer to Figure 1In one embodiment, when the line is electrified when the street light is on, the structure of the line circuit is: the primary of the second transformer T2 (220V / 12v) is supplied with alternating city power from the fire zero line L, N, the end R2 of the street light line acts as an inductor at this time, T2 works, the secondary supplies 12V alternating current to the 1st and 2nd pins of D2 (rectifier bridge), the 4th pin of D2 is negative, connected to the negative of C2 and the line board ground, connected to the negative of the relay coil through R1 and C1, and D1 is an anti-jumping circuit; the positive of the 3rd pin of D2 is connected to the positive of C2, the positive of D1, and the positive of the relay coil, at this time the relay is attracted, the I end (port I) of the relay is disconnected from K1, and the other path is connected to port Rd1, connected to the 3rd pin of LM258 through R3 and D6 to input high level, P1 (isolation power supply 0909) is supplied with 9V DC from the 1st and 2nd pins by the terminal host, and outputs the positive from the 4th pin through R9 and the 2nd pin of LM258, at the same time the 4th pin is connected to VCC, D3, the positive of C4 and C5, R7, and C6, since the 3rd pin of LM258 is connected to input high level, the 1st pin of LM258 also outputs high level at this time, connected to the 2nd pin of U4 through R8, and VCC (9V) is connected to the 1st pin of U4 through D5, at this time the 2nd pin of U4 has a higher level than the 1st pin, D5 and the light emitting diode in the optocoupler are cut off, the 3rd pin (GND) and the 4th pin of U4 are not conductive, i.e. there is no cable breakage signal transmitted to the terminal host, at this time whether the cable is broken is determined by comparing the actual current value of the loop with the preset current threshold. If the current is lower than the threshold, it is determined that the cable is broken.

[0041] Further, the 24-hour anti-theft circuit of the multi-branch cable without external communication mode detects whether the cable is powered off in the electrified state as follows:

[0042] In the line-on state, i.e. the street light line is normally electrified and working, whether the line is stolen and cut is determined by detecting the current threshold, when the detected current is lower than the set threshold, the terminal host actively uploads the undercurrent alarm information, which is the current threshold determination method, specifically:

[0043] When the line is electrified, there is a 220V voltage between the detection points L and N, the second transformer T2 works, supplies power to the relay through the rectifier bridge D2, and the contact is attracted to the normally open end, i.e. the switch K1 is disconnected from port I, the first transformer T1 is disconnected from the non-inverting input terminal of the operational amplifier, at the same time, the second transformer T2 is rectified by the rectifier bridge D2, filtered, and supplied to the non-inverting input terminal of the operational amplifier through port Rd1, resistor R3, and diode D6, the output terminal of the operational amplifier outputs high level, through resistor R8 to the light emitting diode in the optocoupler U4, D5 is cut off, the optocoupler U4 does not emit light, and the low level of the amplification end is transmitted to the host, at this time whether the cable is broken is determined by the current detection threshold of the loop, if the current is lower than the threshold, the host displays the undercurrent / cable breakage alarm.

[0044] Please refer to Figure 2In one embodiment, when the street lamp is off, the line is not electrified, at this time the structure of the line circuit is: the fire zero line L, N does not supply alternating city power to the power transformer T2 (220V / 12v) primary, the street lamp line end R2 at this time acts as a resistor, T2 does not work, at this time the relay is not attracted, the relay I end (port I) is connected with K1, P1 (isolation power 0909) is connected with the 3-pin of LM258 through the positive electrode of the 4-pin output, D3, R2, T1, R5, and a closed circuit is formed, which is connected with C3 positive and R4. At this time, the 3-pin of LM258 inputs high level, the 1-pin of LM258 also outputs high level, which is connected with the 2-pin of U4 through R8, VCC (9V) is connected with the 1-pin of U4 through D5, at this time the 2-pin of U4 is higher than the 1-pin, D5 and the light emitting diode in the optocoupler (U4) are cut off, the 3-pin (GND) and the 4-pin of U4 are not conductive, that is, there is no cable breakage signal to the terminal host, at this time it is judged that the cable line is normal.

[0045] When the cable line is stolen and cut, it is equivalent to the zero line N being disconnected with D3 or the fire line L being disconnected with T1, at this time the 3-pin of LM258 inputs low level, the 1-pin of LM258 also outputs low level, which is connected with the 2-pin of U4 through R8, VCC (9V) is connected with the 1-pin of U4 through D5, at this time the 2-pin of U4 is lower than the 1-pin, D5 and the light emitting diode in the optocoupler (U4) are conductive, the 3-pin (GND) and the 4-pin of U4 are conductive and connected with the terminal host through R6, that is, there is a cable breakage signal to the terminal host.

[0046] The 24-hour anti-theft circuit of the multi-branch cable without external communication mode detects whether the cable is disconnected in a non-electrified state by:

[0047] Further, in the line off state, whether the line closed loop is disconnected is detected, specifically:

[0048] When the line is not powered, the end of the street lamp line zero, the line has a voltage of 250V DC resistance less than 200Ω inductor R2 as the end, with the inductive circuit to form a closed loop, because the street lamp line is not powered, the detection point L and N between no 220V voltage, relay release, normally closed switch K1 connected to the L1 through port I, resistance R5 and the same phase input of the operational amplifier, the fourth interface of the isolation power supply P1 through the diode D3 to the zero line N 9V DC, and then through the zero line to the detection end R2, through the fire line L, the first transformer T1, switch K1, resistance R5 to the same phase input of the operational amplifier provides power 9V, the output of the operational amplifier outputs high level 12V, through the resistance R8 to the light emitting diode inside the optocoupler U4, diode D5 is cut off, the light emitting diode U4 does not emit light and the low level of the amplifier end to the host computer; In the non-light state, when the line is stolen, the fire line or zero line of the street lamp line is disconnected, the fourth interface of the isolation power supply P1 cannot supply power 9V to the third interface of the operational amplifier, the first interface of the operational amplifier outputs low level, the light emitting diode U4 emits light and the diode D5 is turned on to emit light, and the high level of the amplifier end is transmitted to the host computer.

[0049] In this application, unless otherwise clearly specified or limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be interpreted in a broad sense. For example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements, or only surface contact. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0050] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not necessarily for the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0051] In addition, the terms "first", "second", etc. are used only for the purpose of description, and should not be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that the technical solutions described in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A 24-hour theft-proof circuit for multi-branch cable without additional communication mode, characterized in that, The cable detection circuit comprises an isolation power supply P1, one or more induction circuits and one or more detection circuits, the isolation power supply P1 is connected with the plurality of induction circuits and the plurality of detection circuits, each induction circuit matches a detection circuit to form a loop; Each induction circuit comprises a first transformer T1, a second transformer T2, a rectifier bridge D2, a relay and a switch K1, the primary coil of the second transformer T2 is connected with a detection point L and a detection point N, the secondary coil of the second transformer T2 is connected with the relay after being rectified by the rectifier bridge D2, the switch K1 is opened when the relay is powered on, the switch K1 is closed when the relay is powered off, one end of the switch K1 is connected with the primary coil of the first transformer T1, the other end of the switch K1 is connected with a port I, the port I is connected with the detection circuit when the line is not powered, a port Rd1 is arranged between the rectifier bridge D2 and the relay, and the port Rd1 is connected with the detection circuit when the line is powered; Each detection circuit comprises an operational amplifier and an optical coupler U4, the non-inverting input terminal of the operational amplifier is connected with the port Rd1 through a diode D6, a resistor R5 is arranged between the non-inverting input terminal of the operational amplifier and the diode D6, the resistor R5 is connected with the port I, the inverting input terminal of the operational amplifier is connected with the isolation power supply P1, the output terminal of the operational amplifier is connected with the cathode of the optical coupler U4, the anode of the optical coupler U4 is connected with a light emitting diode D5, the emitter of the optical coupler U4 is grounded, and the collector of the optical coupler U4 is connected with the cable through a resistor R6.

2. The 24-hour theft-proof circuit for multi-branch cable without external communication mode according to claim 1, characterized in that, The detection point L and the detection point N of the second transformer T2 are respectively connected with a live wire and a zero line, and the end R2 of a street lamp line is connected between the detection point L and the detection point N as an inductor.

3. The 24-hour theft-proof circuit for multi-branch cable without external communication mode according to claim 1, characterized in that, A capacitor C2 is arranged between the input terminal and the output terminal of the rectifier bridge D2; the relay is connected in parallel with a diode D1, and a capacitor C1 and a resistor R1 are connected in parallel, one end of the capacitor C1 and the resistor R1 is connected with the diode D1 and the relay, and the other end is grounded.

4. The 24-hour theft-proof circuit for multi-branch cable without external communication mode according to claim 1, characterized in that, A resistor R4 and a capacitor C3 are arranged between the resistor R5 and the port I, and the resistor R4 and the capacitor C3 are connected in parallel and grounded.

5. The 24-hour theft-proof circuit for multi-branch cable without external communication mode according to claim 1, characterized in that, A resistor R9 and a resistor R11 are arranged between the fourth interface of the isolation power supply P1 and the inverting input terminal of the operational amplifier, and a capacitor C4, a capacitor C5 and a capacitor C6 connected in parallel are arranged between the resistor R9 and the resistor R11; a resistor R7 is arranged between the fourth interface of the isolation power supply P1 and the resistor R9, and the resistor R7 is connected with the anode of a light emitting diode D4.

6. The 24-hour theft-proof circuit for multi-branch cable without external communication mode according to claim 5, characterized in that, A diode D3 is arranged between the fourth interface of the isolation power supply P1 and the resistor R7, and the other end of the diode D3 is connected with the detection point N of the second transformer T2.

7. The 24-hour theft-proof circuit for multi-drop cable without external communication mode according to claim 1, characterized in that, The induction circuit and the detection circuit are both four-way.

8. The 24-hour theft-proof circuit for multi-drop cable without external communication mode according to claim 1, characterized in that, The operational amplifier is selected from an LM258, and the optical coupler U4 is selected from a PC817.

9. The method of claim 1-8, wherein the method is characterized by, When the line is turned on, that is, the street lamp line is normally powered, whether the line is stolen or not is determined by detecting a current threshold of the street lamp line, when the detected current is lower than a set threshold, the terminal host actively uploads an undercurrent alarm information, which is a current threshold determination mode, and specifically, When the line is electrified, there is 220V voltage between the detection point L and N, the second transformer T2 works, and after rectification by the rectifier bridge D2, the power supply relay attracts the contact to the normally open end, that is, the switch K1 is disconnected with the port I, the first transformer T1 is disconnected with the same phase input terminal of the operational amplifier, at the same time, the second transformer T2 is rectified by the rectifier bridge D2, filtered by the port Rd1, the resistor R3, and the diode D6 to supply power to the same phase input terminal of the operational amplifier, the output terminal of the operational amplifier outputs high level, through the resistor R8 to the light emitting diode inside the optocoupler U4, the diode D5 is cut off, the optocoupler U4 does not emit light, and the low level of the amplification end is transmitted to the host computer. At this time, the current detection threshold value of the road is used to judge whether the current is insufficient to judge whether the cable is disconnected. If it is lower than the current threshold value, the host computer displays the undercurrent / cable disconnection alarm.

10. The method of claim 1-8, wherein the method is a method of detecting a 24-hour theft prevention circuit of a multi-drop cable without an external communication means, characterized in that, In the state of no light on the line, whether the line closed loop circuit is disconnected is detected, specifically: When the line is not electrified, there is a 250V DC resistor less than 200Ω inductor R2 as the end on the zero line and the live line of the street lamp line, which constitutes a closed loop circuit with the induction circuit. Because there is no power on the street lamp line, there is no 220V voltage between the detection point L and N, the relay is released, the normally closed switch K1 is connected with the first transformer T1 through the port I, the resistor R5 and the same phase input terminal of the operational amplifier, the fourth interface of the isolation power supply P1 supplies 9V DC to the zero line N, and then to the detection end R2 through the zero line, the live line L, the first transformer T1, the switch K1, the resistor R5, and the same phase input terminal of the operational amplifier, providing a power supply of 9V. The output terminal of the operational amplifier outputs high level 12V, through the resistor R8 to the light emitting diode inside the optocoupler U4, the diode D5 is cut off, the optocoupler U4 does not emit light, and the low level of the amplification end is transmitted to the host computer. In the state of no light, when the line is stolen and cut, the live line or the zero line of the street lamp line is disconnected, the fourth interface of the isolation power supply P1 cannot supply 9V to the third interface of the operational amplifier, the first interface of the operational amplifier outputs low level, the optocoupler U4 emits light and the diode D5 is turned on, and the high level of the amplification end continuously transmits the cable disconnection signal to the host computer to display the cable disconnection alarm.

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