An interface circuit that multiplexes the ALARM and Ethernet ports based on RJ-45.

Abstract

This invention discloses an interface circuit based on RJ-45 that multiplexes an ALARM port and an Ethernet port. The interface circuit includes a transmission line circuit and a board-compatible circuit. In the transmission line circuit, some pins of the first RJ-45 terminal are connected to the ALARM terminal, and the other pins of the first RJ-45 terminal are connected to the Ethernet port. The second RJ-45 terminal is used to receive a mixed AC / DC signal formed by coupling ALARM, Ethernet, and PoE signals. The board-compatible circuit includes an isolation transformer group and an ALARM signal detection circuit. The isolation transformer group receives the mixed AC / DC signal transmitted from the second RJ-45 terminal and performs AC / DC separation on the mixed signal, transmitting the separated DC signal to the ALARM signal detection circuit. The ALARM signal detection circuit is used to detect the ALARM signal status. This invention couples the ALARM signal with the Ethernet signal, making the ports on the communication device's end panel more streamlined; it can monitor the abnormal status of external user equipment without interfering with PoE power supply and Ethernet communication.

Description

Technical Field

[0001] This invention relates to the field of communication interface technology, and in particular to an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port. Background Technology

[0002] Communication equipment typically has multiple communication signal ports, among which the communication signal ports related to user management include Ethernet ports and ALARM ports (which detect peripheral malfunctions by measuring the voltage between the ALARM+ and ALARM- terminals). Currently, in the designs of most communication equipment manufacturers, these two types of ports are designed independently on the OLT device panel, but this generally presents the following problems:

[0003] First, these two types of ports use different ports and different cables, resulting in inconsistent voltage levels. Setting them as independent ports would require different connecting cables to connect the corresponding devices, which not only increases cable costs but also takes up too much panel port space, crowding out the space of other communication ports.

[0004] Secondly, these two types of ports have different requirements in communication hardware design. For example, network ports require surge protection and electrical isolation, while ALARM ports require a DC power supply. If the ALARM port is directly powered by the internal power supply of the communication equipment, the surge protection requirement cannot be met. In cases where the ALARM cable is long, external lightning strikes induced on the ALARM cable can damage the communication equipment.

[0005] In addition, some manufacturers use the ALARM port to transmit high and low levels to distinguish between abnormal and normal states. The disadvantage of doing so is that the communication equipment needs to be level compatible, which increases the design cost. Summary of the Invention

[0006] The technical problem to be solved by the embodiments of the present invention is to provide an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port, and couples the ALARM signal and Ethernet signal through the transmission line circuit, so that the ports on the communication device end panel are more streamlined; through the board-level compatible circuit, the abnormal status of external user equipment can be monitored without interfering with PoE power supply and Ethernet communication.

[0007] To achieve the above objectives, embodiments of the present invention provide an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port, comprising:

[0008] A transmission line circuit includes a first RJ-45 terminal, a second RJ-45 terminal, and an ALARM terminal. A portion of the pins of the first RJ-45 terminal are connected to the ALARM terminal via a network cable for receiving the ALARM signal from the ALARM port. The other pins of the first RJ-45 terminal are connected to an Ethernet port for receiving Ethernet and PoE signals. The first RJ-45 terminal and the second RJ-45 terminal are connected via a network cable, and the second RJ-45 terminal is used to receive a mixed AC / DC signal formed by the coupling of the ALARM signal, the Ethernet signal, and the PoE signal.

[0009] A board-compatible circuit is provided, which is connected to the second RJ-45 terminal. The board-compatible circuit includes an isolation transformer group and an ALARM signal detection circuit. The isolation transformer group is connected to the second RJ-45 terminal and the ALARM signal detection circuit. The isolation transformer group receives the AC / DC mixed signal transmitted from the second RJ-45 terminal, performs AC / DC separation on the mixed signal, and transmits the separated DC signal to the ALARM signal detection circuit. The ALARM signal detection circuit is used to detect the ALARM signal status.

[0010] As an improvement to the above solution, the first RJ-45 terminal includes four differential pairs, each differential pair including two pins, wherein two differential pairs are connected to PoE+ and PoE- respectively, and the other two differential pairs are connected to ALARM+ and ALARM- respectively.

[0011] As an improvement to the above scheme, the isolation transformer group includes a first isolation transformer, a second isolation transformer, a third isolation transformer, and a fourth isolation transformer;

[0012] The center tap of the first isolation transformer is connected to PoE+, and the center tap of the second isolation transformer is connected to PoE-, for supplying power to external user equipment. The external user equipment is connected in parallel across PoE+ and PoE-.

[0013] The middle tap of the third isolation transformer is connected to ALARM+, and the middle tap of the fourth isolation transformer is connected to ALARM-, for monitoring the ALARM signal status of external user equipment. The external user equipment is connected in parallel to ALARM+ and ALARM-.

[0014] As an improvement to the above solution, the ALARM signal detection circuit includes a first filter sub-circuit, a lightning protection sub-circuit, a second filter sub-circuit, an optocoupler, and a control sub-circuit.

[0015] One end of the first filter sub-circuit is connected to the center tap of the third isolation transformer, and the other end of the first filter sub-circuit is connected to the lightning protection sub-circuit via PoE-.

[0016] One end of the lightning protection sub-circuit is connected to the center tap of the fourth isolation transformer, and the other end of the lightning protection sub-circuit is connected to the second filter sub-circuit.

[0017] The second filter sub-circuit is connected to the input terminal of the optocoupler, and the output terminal of the optocoupler is connected to the control sub-circuit.

[0018] As an improvement to the above scheme, the first filter sub-circuit includes a first resistor, a first capacitor, a second resistor, a second capacitor, and a third resistor; wherein, one end of the third resistor is connected to the center tap of the third isolation transformer, and the other end of the third resistor is connected to the two-stage RC circuit formed by the first resistor, the first capacitor, the second resistor, and the second capacitor, and one end of the first capacitor is connected to PoE+, and the other end of the first capacitor is connected to PoE-.

[0019] As an improvement to the above scheme, the second filter sub-circuit includes a fourth resistor, a third capacitor, a fifth resistor, a sixth resistor, and a fourth capacitor; wherein, the two-stage RC circuit formed by the fourth resistor, the third capacitor, the sixth resistor, and the fourth capacitor is connected in parallel with the lightning protection sub-circuit; one end of the fifth resistor is connected to the third capacitor, and the other end of the fifth resistor is connected to the sixth resistor; the fifth resistor is used for current limiting and voltage division; the lightning protection sub-circuit includes a transient diode; one end of the transient diode is connected to the center tap of the fourth isolation transformer, and the other end of the transient diode is connected to PoE-; the transient diode is used to absorb surges and prevent lightning interference.

[0020] As an improvement to the above scheme, the optocoupler includes a light-emitting diode and a phototransistor. The light-emitting diode is connected in parallel with the fourth capacitor. The collector of the phototransistor is connected to one end of a seventh resistor, the other end of the seventh resistor is connected to a power supply, and the emitter of the phototransistor is grounded.

[0021] As an improvement to the above scheme, the emitter of the phototransistor is also connected to one end of the fifth capacitor, and the other end of the fifth capacitor is connected to the collector of the phototransistor and the control sub-circuit, respectively.

[0022] As an improvement to the above solution, the ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment malfunctions, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are connected. After the current passes through the surge protection sub-circuit for surge protection and lightning protection, it passes through the second filter sub-circuit to filter out noise. The optocoupler is connected to the control sub-circuit. The control sub-circuit detects a low level on the collector of the phototransistor and determines that the ALARM signal is abnormal based on the low level detected by the control sub-circuit.

[0023] As an improvement to the above solution, the ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment is not malfunctioning, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are not connected. No current flows through the light-emitting diode, the optocoupler is not connected to the control sub-circuit, and the control sub-circuit always detects a high level on the collector of the phototransistor. Therefore, the ALARM signal is determined to be normal based on the high level detected by the control sub-circuit.

[0024] Compared to existing technologies, the beneficial effects of the RJ-45-based ALARM port and Ethernet port multiplexing interface circuit provided by this invention are as follows: The ALARM signal and Ethernet signal are coupled through a transmission line circuit, making the ports on the communication equipment's end panel more streamlined and reducing costs; the board-level compatible circuit enables monitoring of abnormal states of external user equipment without interfering with PoE power supply and Ethernet communication, and the ALARM detection circuit quickly detects and responds to anomalies; simultaneously, the ALARM detection circuit includes a surge protection circuit, thus protecting the equipment and reducing the impact of lightning strikes even when the ALARM port is connected to a long cable. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a preferred embodiment of an interface circuit based on RJ-45 that multiplexes ALARM and Ethernet ports, provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the ALARM signal in a preferred embodiment of an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port, provided by the present invention.

[0027] Figure 3 This is a schematic diagram of the connection of the first RJ-45 terminal in a preferred embodiment of an interface circuit based on RJ-45 that multiplexes ALARM and Ethernet ports, provided by the present invention.

[0028] Figure 4 This is a schematic diagram of a board-compatible circuit in a preferred embodiment of an interface circuit based on RJ-45 that multiplexes ALARM and Ethernet ports, provided by the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figure 1 , Figure 1 This is a schematic diagram of a preferred embodiment of an interface circuit based on RJ-45 that multiplexes an ALARM port and an Ethernet port, provided by the present invention. The interface circuit based on RJ-45 that multiplexes an ALARM port and an Ethernet port includes:

[0031] A transmission line circuit includes a first RJ-45 terminal, a second RJ-45 terminal, and an ALARM terminal. A portion of the pins of the first RJ-45 terminal are connected to the ALARM terminal via a network cable for receiving the ALARM signal from the ALARM port. The other pins of the first RJ-45 terminal are connected to an Ethernet port for receiving Ethernet and PoE signals. The first RJ-45 terminal and the second RJ-45 terminal are connected via a network cable, and the second RJ-45 terminal is used to receive a mixed AC / DC signal formed by the coupling of the ALARM signal, the Ethernet signal, and the PoE signal.

[0032] A board-compatible circuit is provided, which is connected to the second RJ-45 terminal. The board-compatible circuit includes an isolation transformer group and an ALARM signal detection circuit. The isolation transformer group is connected to the second RJ-45 terminal and the ALARM signal detection circuit. The isolation transformer group receives the AC / DC mixed signal transmitted from the second RJ-45 terminal, performs AC / DC separation on the mixed signal, and transmits the separated DC signal to the ALARM signal detection circuit. The ALARM signal detection circuit is used to detect the ALARM signal status.

[0033] Specifically, this invention is based on RJ-45 interface and PoE technology. On one hand, a specially designed RJ-45 transmission line is used as a carrier to couple the ALARM signal and Ethernet signal together to the RJ-45 terminal at the other end of the cable. On the other hand, the communication equipment is designed with an RJ-45-based interface circuit. The interface is connected to an isolation and protection device for protection. At the same time, it is combined with the DC level supplied by the PoE circuit to the ALARM signal, so that it can monitor the abnormality of the external user side through the ALARM signal detection circuit and report the ALARM signal. The detection process does not interfere with the PoE power supply function to the external user equipment. The Ethernet signal is connected to its corresponding transceiver circuit in the device, completing the separation and decoupling of the two signals, and realizing the multiplexing of ALARM and Ethernet signals on the same RJ-45. The present invention provides an interface circuit for multiplexing an ALARM port and an Ethernet port based on RJ-45, including a transmission line circuit and a board-compatible circuit. The transmission line circuit includes a first RJ-45 terminal, a second RJ-45 terminal, and an ALARM terminal. Some pins of the first RJ-45 terminal are connected to the ALARM terminal via a network cable for receiving the ALARM signal from the ALARM port. The ALARM terminal is connected to the ALARM port. Other pins of the first RJ-45 terminal are connected to the Ethernet port for receiving Ethernet signals and PoE signals. The first RJ-45 terminal and the second RJ-45 terminal are connected via a network cable. The second RJ-45 terminal is used to receive the AC / DC mixed signal formed by the coupling of the ALARM signal, the Ethernet signal, and the PoE signal. The board-compatible circuit is connected to the second RJ-45 terminal via an Ethernet port. The board-compatible circuit includes an isolation transformer group and an ALARM signal detection circuit. The isolation transformer group is connected to the second RJ-45 terminal and the ALARM signal detection circuit. The isolation transformer group receives the AC / DC mixed signal transmitted from the second RJ-45 terminal and performs AC / DC separation on the AC / DC mixed signal. The separated DC signal is then transmitted to the ALARM signal detection circuit, which is used to detect the ALARM signal status.

[0034] It should be noted that you should refer to [link / reference]. Figure 2 , Figure 2This is a schematic diagram of the ALARM signal in a preferred embodiment of an interface circuit based on RJ-45 multiplexing of the ALARM port and Ethernet port provided by the present invention. Anomaly detection is achieved by detecting the state of the user-side ALARM switch K1. The ALARM line terminals are connected to the monitoring equipment, where ALARM+ and ALARM- are connected to the two ends of the switch or relay K1. When an anomaly occurs on the user side, the switch or relay K1 is closed under the control of the sensor circuit, resulting in current flowing through ALARM+ and ALARM-, causing the ALARM terminal voltage to drop, and the ALARM signal becomes active. When the anomaly is resolved, the switch K1 opens, no current flows through ALARM+ and ALARM-, and the ALARM signal becomes invalid.

[0035] In this embodiment, both the Ethernet port and the ALARM port are user-side ports, while the communication device only has one Ethernet port. The transmission line circuit includes a first RJ-45 terminal (connected to the user-side Ethernet port), an ALARM terminal (connected to the user-side ALARM port), and a second RJ-45 terminal (connected to the communication device's Ethernet port, which is then connected to a board-level compatible circuit). This reduces the number of panel ports on the communication device side. Through the board-level compatible circuit, abnormal states of external user equipment can be monitored without interfering with PoE power supply and Ethernet communication.

[0036] In another preferred embodiment, the first RJ-45 terminal includes four differential pairs, each differential pair including two pins, wherein two differential pairs are connected to PoE+ and PoE- respectively, and the other two differential pairs are connected to ALARM+ and ALARM- respectively.

[0037] For details, please refer to Figure 3 , Figure 3 This is a schematic diagram of the connection of the first RJ-45 terminal in a preferred embodiment of an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port. Since the Ethernet signal is a high-frequency differential signal, the ALARM signal is a DC signal (with two states: on or off), and PoE is a DC power supply, and the RJ-45 transmission line is in the form of a network cable with four differential pairs and a total of eight signal pins, sufficient for the coexistence of these signals, these signals can coexist on the network cable based on a reasonable pair allocation. In this embodiment, two differential pairs of the first RJ-45 terminal are connected to PoE+ and PoE- respectively, and the other two differential pairs are connected to ALARM+ and ALARM- respectively. For example, pair 12 (pins 1 and 2) is connected to PoE-, pair 36 (pins 3 and 6) is connected to PoE+, pair 45 (pins 4 and 5) is connected to ALARM+, and pair 78 (pins 7 and 8) is connected to ALARM-. These four pairs serve as the transmission medium for the Ethernet signal.

[0038] It should be noted that the above connection involves connecting ALARM and PoE to the corresponding pins inside the network cable. The RJ-45 terminal itself does not require special treatment and only needs to be compatible with a standard RJ-45 port.

[0039] In yet another preferred embodiment, the isolation transformer group includes a first isolation transformer, a second isolation transformer, a third isolation transformer, and a fourth isolation transformer;

[0040] The center tap of the first isolation transformer is connected to PoE+, and the center tap of the second isolation transformer is connected to PoE-, for supplying power to external user equipment. The external user equipment is connected in parallel across PoE+ and PoE-.

[0041] The middle tap of the third isolation transformer is connected to ALARM+, and the middle tap of the fourth isolation transformer is connected to ALARM-, for monitoring the ALARM signal status of external user equipment. The external user equipment is connected in parallel to ALARM+ and ALARM-.

[0042] For details, please refer to Figure 4 , Figure 4 This is a schematic diagram of a board-level compatible circuit in a preferred embodiment of an interface circuit based on RJ-45 multiplexing of ALARM and Ethernet ports provided by the present invention. The second RJ-45 terminal connects to the board-level compatible circuit, and couples the mixed signal to the circuitry on the PCB board. The mixed signal then reaches the isolation transformer bank, where AC / DC separation is achieved. Since the Ethernet signal is a high-frequency AC signal, it is directly coupled to the internal circuitry of the device through the isolation transformer. The PoE signal is a DC signal, equivalent to a power source for the communication equipment. It is coupled to the external user equipment through the center tap of the 12- and 36-pair isolation transformer (user-end appliances are connected in parallel across PoE+ and PoE-). The ALARM signal is also a DC signal and requires PoE voltage as its excitation source. Therefore, PoE+ is connected to a resistive load and a two-stage RC filter circuit to filter out high-frequency noise in the PoE power supply. It is then coupled to the external user equipment by the 45-pair center tap and transmission line circuit.

[0043] It should be noted that the PoE circuit formed by PoE+ and PoE- in this embodiment can not only supply power to the external user equipment, but also draw power from the external PoE power supply device, and neither of these will affect the ALARM and Ethernet communication functions.

[0044] In yet another preferred embodiment, the ALARM signal detection circuit includes a first filter sub-circuit, a lightning protection sub-circuit, a second filter sub-circuit, an optocoupler, and a control sub-circuit.

[0045] One end of the first filter sub-circuit is connected to the center tap of the third isolation transformer, and the other end of the first filter sub-circuit is connected to the lightning protection sub-circuit via PoE-.

[0046] One end of the lightning protection sub-circuit is connected to the center tap of the fourth isolation transformer, and the other end of the lightning protection sub-circuit is connected to the second filter sub-circuit.

[0047] The second filter sub-circuit is connected to the input terminal of the optocoupler, and the output terminal of the optocoupler is connected to the control sub-circuit.

[0048] Specifically, the ALARM signal detection circuit includes a first filter sub-circuit, a surge protection sub-circuit, a second filter sub-circuit, an optocoupler, and a control sub-circuit. One end of the first filter sub-circuit is connected to the center tap of the third isolation transformer, and the other end is connected to the surge protection sub-circuit via PoE-. One end of the surge protection sub-circuit is connected to the center tap of the fourth isolation transformer, and the other end is connected to the second filter sub-circuit. The second filter sub-circuit is connected to the input terminal of the optocoupler, and the output terminal of the optocoupler is connected to the control sub-circuit. The ALARM signal detection circuit can detect the ALARM state (user-end abnormality) under electrical isolation. The left circuit corresponds to ALARM+, and the right circuit corresponds to ALARM-. When an ALARM state occurs, the ALARM+ and ALARM- of the user-end monitoring device are connected together via a switch or relay. If PoE+ is used as the positive power supply and PoE- as the negative power supply, the current direction is PoE+, to the left circuit, to the user-end monitoring device, to the center tap of ALARM- in the right circuit, and then back to PoE- to complete the loop.

[0049] It should be noted that the form or number of ALARM ports in this embodiment is not limited, and multiple ALARM ports can be connected in parallel (to connect multiple monitoring devices), but it must be ensured that ALARM+ and ALARM- are connected to different wire pairs of the RJ-45 interface to prevent short circuits.

[0050] In another preferred embodiment, the first filter sub-circuit includes a first resistor, a first capacitor, a second resistor, a second capacitor, and a third resistor; wherein, one end of the third resistor is connected to the center tap of the third isolation transformer, and the other end of the third resistor is connected to a two-stage RC circuit formed by the first resistor, the first capacitor, the second resistor, and the second capacitor, and one end of the first capacitor is connected to PoE+, and the other end of the first capacitor is connected to PoE-.

[0051] Specifically, the first filter sub-circuit includes a first resistor R1, a first capacitor C1, a second resistor R2, a second capacitor C2, and a third resistor R3; wherein, one end of the third resistor R3 is connected to the center tap of the third isolation transformer, and the other end of the third resistor R3 is connected to the two-stage RC circuit formed by the first resistor R1, the first capacitor C1, the second resistor R2, and the second capacitor C2, and one end of the first capacitor C1 is connected to PoE+, and the other end of the first capacitor C1 is connected to PoE-.

[0052] In another preferred embodiment, the second filter sub-circuit includes a fourth resistor, a third capacitor, a fifth resistor, a sixth resistor, and a fourth capacitor; wherein, the two-stage RC circuit formed by the fourth resistor, the third capacitor, the sixth resistor, and the fourth capacitor is connected in parallel with the lightning protection sub-circuit; one end of the fifth resistor is connected to the third capacitor, and the other end of the fifth resistor is connected to the sixth resistor; the fifth resistor is used for current limiting and voltage division; the lightning protection sub-circuit includes a transient diode, one end of which is connected to the center tap of the fourth isolation transformer, and the other end of which is connected to PoE-; the transient diode is used to absorb surges and prevent lightning interference.

[0053] Specifically, the second filter sub-circuit includes a fourth resistor R4, a third capacitor C3, a fifth resistor R5, a sixth resistor R6, and a fourth capacitor C4. The two-stage RC circuit formed by the fourth resistor R4, third capacitor C3, sixth resistor R6, and fourth capacitor C4 is connected in parallel with the lightning protection sub-circuit. One end of the fifth resistor R5 is connected to the third capacitor C3, and the other end of the fifth resistor R5 is connected to the sixth resistor R6. The fifth resistor R5 is used for current limiting and voltage division. The lightning protection sub-circuit includes a transient diode. One end of the transient diode is connected to the center tap of the fourth isolation transformer, and the other end of the transient diode is connected to PoE-. The transient diode is used to absorb surges and prevent lightning interference.

[0054] In another preferred embodiment, the optocoupler includes a light-emitting diode and a phototransistor. The light-emitting diode is connected in parallel with the fourth capacitor. The collector of the phototransistor is connected to one end of a seventh resistor, the other end of the seventh resistor is connected to a power supply, and the emitter of the phototransistor is grounded.

[0055] Specifically, the optocoupler includes a light-emitting diode (LED) and a phototransistor. The LED is connected in parallel with the fourth capacitor C4. The collector of the phototransistor is connected to one end of the seventh resistor R7, and the other end of the seventh resistor R7 is connected to the power supply. The emitter of the phototransistor is grounded.

[0056] In another preferred embodiment, the emitter of the phototransistor is also connected to one end of a fifth capacitor, and the other end of the fifth capacitor is connected to the collector of the phototransistor and the control sub-circuit, respectively.

[0057] Specifically, the emitter of the phototransistor is also connected to one end of the fifth capacitor C5, and the other end of the fifth capacitor C5 is connected to the collector of the phototransistor and the control sub-circuit, respectively.

[0058] In another preferred embodiment, the ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment malfunctions, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are connected. After the current passes through the surge protection sub-circuit for surge protection and lightning protection, it passes through the second filter sub-circuit to filter out noise. The optocoupler is connected to the control sub-circuit. The control sub-circuit detects a low level on the collector of the phototransistor and determines that the ALARM signal is abnormal based on the low level detected by the control sub-circuit.

[0059] Specifically, the ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment malfunctions, ALARM+, which is connected to the middle tap of the third isolation transformer, and ALARM-, which is connected to the middle tap of the fourth isolation transformer, are connected. After the current is protected against surges and lightning by the surge protection sub-circuit, it is limited and voltage divided by resistor R5 to protect the optocoupler. The second filter sub-circuit filters out noise (because the ALARM line is relatively long and easily introduces interference signals, RC filtering is needed to prevent false triggering), causing the optocoupler Q1 to light up and connecting the VCC-R7-GND1 path of the secondary side of the isolation circuit. R7 acts as a current-limiting resistor to limit the current of the phototube in Q1, while C5 is a reserved device used to eliminate level glitches and prevent false triggering. The optocoupler is connected to the control sub-circuit, which can then detect the low level on the collector of the phototransistor and determine that the ALARM signal is abnormal based on the low level detected by the control sub-circuit.

[0060] In another preferred embodiment, the ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment is not malfunctioning, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are not connected. No current flows through the light-emitting diode, the optocoupler is not connected to the control sub-circuit, and the control sub-circuit always detects a high level on the collector of the phototransistor. Based on the high level detected by the control sub-circuit, the ALARM signal is determined to be normal.

[0061] Specifically, when the ALARM port of the external user equipment is connected to the ALARM terminal, and the ALARM+ connected to the middle tap of the third isolation transformer and the ALARM- connected to the middle tap of the fourth isolation transformer are not connected when the external user equipment is not malfunctioning, no current flows through the light-emitting diode, the optocoupler is not connected to the control sub-circuit, and the control sub-circuit always detects a high level on the collector of the phototransistor. Therefore, the ALARM signal is determined to be normal based on the high level detected by the control sub-circuit.

[0062] This embodiment can monitor anomalies of user equipment without interfering with PoE power supply and Ethernet communication. It can also quickly detect and respond to anomalies through an ALARM detection circuit. In addition, the ALARM detection circuit includes a surge protection circuit, so that the equipment can be protected and the impact of lightning strikes can be reduced even when the ALARM port is connected to a long cable.

[0063] This invention provides an interface circuit based on RJ-45 that multiplexes the ALARM port and Ethernet port. The ALARM signal and Ethernet signal are coupled through a transmission line circuit, simplifying the ports on the communication device's front panel and reducing costs. Through board-level compatible circuitry, abnormal states of external user equipment can be monitored without interfering with PoE power supply and Ethernet communication, and an ALARM detection circuit can quickly detect and respond to anomalies. Simultaneously, the ALARM detection circuit includes a surge protection circuit, protecting the device and reducing the impact of lightning strikes even when the ALARM port is connected to a long cable.

[0064] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An interface circuit based on RJ-45 that multiplexes ALARM and Ethernet ports, characterized in that, include: A transmission line circuit includes a first RJ-45 terminal, a second RJ-45 terminal, and an ALARM terminal. A portion of the pins of the first RJ-45 terminal are connected to the ALARM terminal via a network cable for receiving the ALARM signal from the ALARM port. The other pins of the first RJ-45 terminal are connected to an Ethernet port for receiving Ethernet and PoE signals. The first RJ-45 terminal and the second RJ-45 terminal are connected via a network cable, and the second RJ-45 terminal is used to receive a mixed AC / DC signal formed by the coupling of the ALARM signal, the Ethernet signal, and the PoE signal. A board-compatible circuit is provided, which is connected to the second RJ-45 terminal. The board-compatible circuit includes an isolation transformer group and an ALARM signal detection circuit. The isolation transformer group is connected to the second RJ-45 terminal and the ALARM signal detection circuit. The isolation transformer group receives the AC / DC mixed signal transmitted from the second RJ-45 terminal, performs AC / DC separation on the mixed signal, and transmits the separated DC signal to the ALARM signal detection circuit. The ALARM signal detection circuit is used to detect the ALARM signal status.

2. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 1, characterized in that, The first RJ-45 terminal includes four differential pairs, each differential pair including two pins, wherein two differential pairs are connected to PoE+ and PoE- respectively, and the other two differential pairs are connected to ALARM+ and ALARM- respectively.

3. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 2, characterized in that, The isolation transformer group includes a first isolation transformer, a second isolation transformer, a third isolation transformer, and a fourth isolation transformer; The center tap of the first isolation transformer is connected to PoE+, and the center tap of the second isolation transformer is connected to PoE-, for supplying power to external user equipment. The external user equipment is connected in parallel across PoE+ and PoE-. The middle tap of the third isolation transformer is connected to ALARM+, and the middle tap of the fourth isolation transformer is connected to ALARM-, for monitoring the ALARM signal status of external user equipment. The external user equipment is connected in parallel to ALARM+ and ALARM-.

4. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 3, characterized in that, The ALARM signal detection circuit includes a first filter sub-circuit, a lightning protection sub-circuit, a second filter sub-circuit, an optocoupler, and a control sub-circuit. One end of the first filter sub-circuit is connected to the center tap of the third isolation transformer, and the other end of the first filter sub-circuit is connected to the lightning protection sub-circuit via PoE-. One end of the lightning protection sub-circuit is connected to the center tap of the fourth isolation transformer, and the other end of the lightning protection sub-circuit is connected to the second filter sub-circuit. The second filter sub-circuit is connected to the input terminal of the optocoupler, and the output terminal of the optocoupler is connected to the control sub-circuit.

5. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 4, characterized in that, The first filter sub-circuit includes a first resistor, a first capacitor, a second resistor, a second capacitor, and a third resistor; wherein, one end of the third resistor is connected to the center tap of the third isolation transformer, and the other end of the third resistor is connected to a two-stage RC circuit formed by the first resistor, the first capacitor, the second resistor, and the second capacitor, and one end of the first capacitor is connected to PoE+, and the other end of the first capacitor is connected to PoE-.

6. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 5, characterized in that, The second filter sub-circuit includes a fourth resistor, a third capacitor, a fifth resistor, a sixth resistor, and a fourth capacitor; wherein, the two-stage RC circuit formed by the fourth resistor, the third capacitor, the sixth resistor, and the fourth capacitor is connected in parallel with the lightning protection sub-circuit; one end of the fifth resistor is connected to the third capacitor, and the other end of the fifth resistor is connected to the sixth resistor; the fifth resistor is used for current limiting and voltage division; the lightning protection sub-circuit includes a transient diode; one end of the transient diode is connected to the center tap of the fourth isolation transformer, and the other end of the transient diode is connected to PoE-; the transient diode is used to absorb surges and prevent lightning interference.

7. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 6, characterized in that, The optocoupler includes a light-emitting diode and a phototransistor. The light-emitting diode is connected in parallel with the fourth capacitor. The collector of the phototransistor is connected to one end of a seventh resistor, the other end of the seventh resistor is connected to a power supply, and the emitter of the phototransistor is grounded.

8. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 7, characterized in that, The emitter of the phototransistor is also connected to one end of the fifth capacitor, and the other end of the fifth capacitor is connected to the collector of the phototransistor and the control sub-circuit, respectively.

9. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 8, characterized in that, The ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment malfunctions, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are connected. After the current passes through the surge protection sub-circuit for surge protection and lightning protection, it passes through the second filter sub-circuit to filter out noise. The optocoupler is connected to the control sub-circuit. The control sub-circuit detects a low level on the collector of the phototransistor and determines that the ALARM signal is abnormal based on the low level detected by the control sub-circuit.

10. The interface circuit for multiplexing RJ-45 ALARM and Ethernet ports as described in claim 8, characterized in that, The ALARM port of the external user equipment is connected to the ALARM terminal. When the external user equipment is not malfunctioning, ALARM+ connected to the middle tap of the third isolation transformer and ALARM- connected to the middle tap of the fourth isolation transformer are not connected. No current flows through the light-emitting diode. The optocoupler is not connected to the control sub-circuit. The control sub-circuit always detects a high level on the collector of the phototransistor. Based on the high level detected by the control sub-circuit, the ALARM signal is determined to be normal.

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