CN108259102B - Double-conductor fire-fighting public broadcasting system with fault alarm function - Google Patents

Abstract

The invention relates to a double-wire fire-fighting public broadcasting system with a fault alarm function, which comprises a sound source, wherein the sound source is connected with a power amplifier, a double-wire loop is connected with a matching transformer and a loudspeaker through a parallel circuit, an isolation capacitor is inserted into the position, close to an output transformer, on the double-wire loop, and provides an alternating current signal channel for the double-wire loop, and simultaneously blocks direct current from passing through to cause direct current circuit breaking; the double-conductor loop is connected with a direct-current power supply, and the direct-current power supply is connected with the double-conductor loop to form a direct-current loop; and a fault alarm unit and a branch isolation capacitor are arranged on the parallel circuit, the fault alarm unit and the primary coil of the matching transformer are connected, and two ends of the branch isolation capacitor are respectively connected with the current input end and the current output end of the fault alarm unit. The audio alternating current circuit, the direct current power supply circuit and the wireless communication circuit of the double-wire fire-fighting public broadcasting system can effectively coexist. And in a two-wire loop form, the dual standards of fire fighting and public broadcasting are simultaneously met.

Description

Double-conductor fire-fighting public broadcasting system with fault alarm function

Technical Field

The invention relates to an emergency broadcasting system, in particular to a double-conductor fire-fighting public broadcasting system with a fault alarm function.

Background

According to the national standard of fire-fighting broadcasting, such a system actually applies and transmits 3 voltage signals with very different characteristics.

The first is an audio signal. This is a powerful signal that is generated and output by a power amplifier to drive one or more speakers. Its instantaneous power may range from tens of watts to thousands of watts, as desired. The frequency range may cover from 80Hz to 20 KHz. The audio signal itself is a random signal belonging to a mixture of multiple frequencies, either power or frequency exhibiting unpredictable characteristics.

The second signal is a digital communication signal. The method is mainly used for reporting whether system components are in fault or not. The transmission of such signals may be intermittent, but each transmission must adhere to the characteristics of the digital signal. First, it is a low power signal, with an output in the milliwatt range. The power of an audio signal is generally at least tens to tens of thousands of times greater than its power.

The third is a dc power supply. It is a fixed dc voltage and does not carry any signal. It exists primarily for the purpose of providing dc power to circuits that generate digital signals. It provides power from a few watts to tens of watts, 1 to 3 orders of magnitude less than audio power, depending on the number of speakers it serves. These 3 signals, whether in power, frequency, voltage, all have a large difference; any attempt to make them coexist on the same two-conductor loop and to enable each, individual, separate application, without interference from the other 2 signals, is an extremely difficult endeavor.

Taking the emergency broadcasting system existing in the current market as an example, except that the audio quality is often in a state close to the minimum standard; for the hard requirement of real-time (less than 100 seconds) fault alarm, the 2 to 4 wires must be additionally used for passing detection besides the audio output double wires.

As shown in the circuit structure diagram of fig. 1, the conventional public address system includes anaudio source 101, an audio source connected to apower amplifier 102, thepower amplifier 102 connected to a two-wire loop 104, the two-wire loop 104 connected to amatching transformer 106 and aspeaker 107 through aparallel circuit 105, the two-wire loop 104 provided with anoutput transformer 103 connected to an output terminal of thepower amplifier 102, and an output signal of theaudio source 101 entering thepower amplifier 102 is amplified to a desired power and output to a primary side of theoutput transformer 103. Here, thepower amplifier 102 is a power amplifier belonging to class AB or class C.

Theoutput transformer 103 is a power matched voltage boost device. According to the international standard, the secondary output voltage of theoutput transformer 103 is divided into 70V p-p and 100V p-p peak-to-peak. Fire-fighting broadcasting also has equipment that uses 120V p-p as an output voltage.

The reason for the high voltage is because of the need for the two-wire loop 104 to be resistance matched. First, the two-wire loop 104 may be up to 100 meters or more in length. For cost savings, wire resistances in the range of 0.1ohm per meter are usually chosen. A 100 meter loop (200 meters total length) produces an impedance of 20 ohms. According to Ohm's law, a current of every 1Amp flows through a 100 meter loop, causing a voltage drop of 20V. Therefore, high voltage transmission is a necessary solution.

The driving power of eachspeaker 107 is inputted through theparallel circuit 105 and the matchingtransformer 106. The impedance of theusual loudspeaker 107 is 2, 4, 8, 16 ohm. Taking thespeaker 107 with 6W power and 4ohm impedance as an example, the theoretical value of the peak driving voltage can be calculated as follows:

W2/R means power 6W, V means peak driving voltage, and R means impedance 4ohm, which means V4.9V.

Therefore, the theoretical value of the primary input voltage of the matchingtransformer 106 is 100V, and the theoretical value of the secondary output voltage is 4.9V. Based on this data, thebest matching transformer 106 can be designed. If the output power of thepower amplifier 102 is 240 watts, theoretically this public address system can be installed with up to 40speakers 107 of 6 watts.

Fig. 2 is a circuit configuration diagram of another conventional public address system. It is a traditional high voltage broadcast system, using class D power amplifiers. The structure of such a system is substantially the same as the system of fig. 1; the only difference is that it omits theoutput transformer 103. This is because the class D power amplifier has a capability of directly outputting a high voltage, and can directly output a spike voltage of 70V or 100V. Theoutput transformer 103 having a boosting function can be omitted, but the addition of theoutput transformer 103 is not excluded if there is a special need.

The above common public address systems have no fault alarm requirements and they use only two conductor loops. If the system needs to be upgraded into a fire-fighting broadcasting system, additional wiring is needed by adopting the existing equipment on the market, and the construction difficulty is greatly increased.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides a double-conductor fire-fighting public broadcasting system with a fault alarm function.

In order to achieve the purpose, the invention adopts the technical scheme that:

a double-wire fire-fighting public broadcasting system with fault alarm comprises a sound source, wherein the sound source is connected with a power amplifier, the power amplifier is connected with a double-wire loop, the double-wire loop is connected with a matching transformer and a loudspeaker through a parallel circuit, an isolation capacitor is inserted in the position, close to an output transformer, of the double-wire loop, the isolation capacitor provides an alternating current signal channel for the double-wire loop, and simultaneously blocks direct current from passing through to cause direct current circuit breaking;

the double-wire loop is connected with a direct current power supply, two ends of the isolation capacitor are respectively connected with the anode and the cathode of the direct current power supply, and the direct current power supply and the double-wire loop are connected to form a direct current loop;

and a fault alarm unit and a branch isolation capacitor are arranged on the parallel circuit, the fault alarm unit and the primary coil of the matching transformer are connected, and two ends of the branch isolation capacitor are respectively connected with the current input end and the current output end of the fault alarm unit.

Furthermore, the power amplifier is an AB type or C type power amplifier, and an output transformer connected with the output end of the power amplifier is arranged on the double-lead loop.

Furthermore, the power amplifier is a D-type power amplifier, and an isolation inductor is arranged between the end points of the input double-conductor loop of the power amplifier;

the isolation inductor prevents direct current from breaking down the class D power amplifier through a direct current channel with theoretically zero impedance, and isolates a node of an input double-conductor loop of the class D power amplifier. If special needs exist, the isolation inductor can still be replaced by an output transformer.

Furthermore, the fault alarm unit consists of a direct current power supply module, a micro control unit, a load monitoring module and a wireless communication module;

the direct-current power supply module ensures that the working voltage of the fault alarm unit is stabilized within a designed numerical range;

the micro control unit controls the load monitoring module to continuously monitor the parallel circuit, the matching transformer and the loudspeaker;

the load monitoring module judges whether the loudspeaker and the connecting circuit thereof work normally or not by monitoring the load of the loudspeaker.

The communication module can have two options: the wireless communication module and the wired communication module; corresponding to the wireless control communication loop and the wired communication control loop, respectively, described below.

Further, the design of the two-wire loop connection control communication loop can be two types: a wireless control communication loop and a wired control communication loop.

The wireless control communication loop is composed of a system controller, a fault information wireless collector and an antenna which are connected with each other, the antenna is connected with an antenna signal of the fault wireless alarm unit through a wireless communication channel, and the system controller is connected with a sound source.

The wired control communication loop consists of a system controller, a signal modem and a communication signal matching transformer which are connected with each other. The frequency of the modulated communication signal is far higher than that of the audio signal, the communication signal crosses into the double-conductor through the communication signal matching transformer, and the communication is carried out with the micro-control unit through the demodulation function of the wired communication module. The modulation signal returned from the micro control unit is demodulated by the signal modem and then input to the system control to make appropriate response.

Further, the sound source is a digital audio player or an analog audio player or a real-time audio player.

Further, the parallel circuit is plural.

Further, the load monitoring module is an electromagnetic sensing module such as a Hall effect (Hall effect) monitoring element or other current measuring elements.

Further, the wireless communication module is an IEEE802.11 series, Zigbee, bluetooth module, or the like. ISM bands may also be selected for use such as: 433MHz, 902MHz and the like, and a self-defined communication protocol is matched, so that the reliability and the stability of the fault wireless alarm unit are ensured. The wireless communication module is connected with the antenna and provides a wireless transmitting function.

Furthermore, the wired communication module is connected with the double-conductor control communication loop through a communication signal matching transformer. The communication signal generated by the micro control unit is input into the modem in the module. After modulation, the signal flows into the double-conductor control communication loop through the communication signal matching transformer. The control signal flowing from the two-wire control communication loop is matched with the modem of the transformer flowing module through the communication signal. The demodulated signal is input into the micro control unit.

The invention has the beneficial effects that: the audio alternating current circuit, the direct current supply circuit and the wireless or wired communication circuit of the double-wire fire-fighting public broadcasting system can effectively coexist. And in a two-wire loop form, the dual standards of fire fighting and public broadcasting are simultaneously met.

Drawings

FIG. 1 is a circuit configuration diagram of a conventional public address system using class AB and class C power amplifiers;

fig. 2 is a circuit configuration diagram of a conventional public address system using a class D power amplifier;

FIG. 3 is a circuit diagram of a two-wire public address and fault alarm complex system using class AB and class C power amplifiers according to the present invention after improvement;

FIG. 4 is a circuit diagram of a two-wire public address and fault alarm complex system using class D power amplifier after improvement of the present invention;

FIG. 5 is an internal layout view of a wireless alarm unit for faults according to the present invention;

FIG. 6 is a schematic diagram of a two-conductor three-loop public address and fault wireless alarm combination system of the present invention;

FIG. 7 is a schematic diagram of a two-conductor three-circuit public broadcasting and fault cable alarm complex system of the present invention;

FIG. 8 is an internal layout view of a wireless alarm unit for faults in accordance with the present invention;

FIG. 9 is a layout diagram of a wired communication module according to the present invention;

fig. 10 is a schematic view of a building in which a broadcasting system is installed on the second floor according to an embodiment of the present invention;

fig. 11 is a schematic diagram of a building in which a broadcasting system is installed in a first floor according to an embodiment of the present invention.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

As shown in fig. 3 to 6, the two-wire fire-fighting public broadcasting system using wireless communication as fault alarm is shown, and fig. 3 is a task of the present invention based on the conventional technical scheme of fig. 1, adding an innovative circuit to complete the two-wire burden, and simultaneously providing an audio broadcasting function, a wireless alarm function of component faults, and a dc power supply required for completing the alarm function.

First, the audio broadcasting is still based on the structure of fig. 1, but anisolation capacitor 202 is inserted in the two-wire loop 104 near theoutput transformer 103. The main function of thisisolation capacitor 202 is to provide a channel for the two-wire loop 104 to pass an ac signal (audio broadcast signal); and simultaneously, the direct current is blocked from passing, so that the direct current is disconnected. Then, the output of thedc power supply 201 is connected to both ends of theisolation capacitor 202, and the terminal 205 is positive and the terminal 206 is negative, respectively. This arrangement allows the two-wire loop 104 to operate an ac loop and a dc loop simultaneously without interfering with each other.

An alternating current loop: an ac signal is input into the two-wire loop 104 from theoutput transformer 103 and then flows into the branchparallel circuit 105 through thenode 209. One of the two branches allows the audio (ac) signal to flow through the primary of the matchingtransformer 106, enabling its secondary to drive thespeaker 107. The ac current is then input to the faultywireless alarm unit 204 viaterminal 212. Due to the design of the fault radio alarm unit 204 (see fig. 5), its impedance for ac is much larger than thebranch isolation capacitance 203. The ac must flow throughterminal 208, throughbranch isolation capacitor 203, and back to the two-wire loop 104 throughnode 210. Then continues to flow through theisolation capacitor 202 back to theoutput transformer 103, completing the ac loop.

A direct current loop: the positive pole of thedc power supply 201 enters the two-wire loop 104 throughterminal 205. The dc current flows through the secondary of the theoretical zeroimpedance output transformer 103 throughterminal 209 into theparallel circuit 105; one of the two branches allows dc current to flow through the primary of the matchingtransformer 106. Theoretically, it is zero impedance to direct current. The dc power then enters the faultywireless alarm unit 204 through the terminal 212.

Due to the design structure of the wireless alarm unit 204 (see fig. 5), the direct current will pass through the power module 501(DC/DC conversion circuit) to provide power to thewireless alarm unit 204. Since theisolation capacitor 203 is theoretically an insulator to dc and has a much higher impedance than thewireless alarm unit 204, dc current flows directly to the terminal 207 and then to the two-wire loop 104 via theterminal 210. After reaching thenegative terminal 206 of theisolation capacitor 202, theisolation capacitor 202 is disconnected from the dc power, and only flows to the negative terminal of thedc power supply 201, thereby completing the dc loop.

Each faultywireless alarm unit 204 monitors the health of the correspondingparallel circuit 105, matchingtransformer 106,speaker 107. If any faults are found, the fault information is reported to the fault information wireless collector 302 in real time through a wireless communication mode. The fault information is reported by the wireless collector 302 to the system controller 301 (see fig. 6). This process takes place within the time frame specified by the fire standards (currently less than 100 seconds), completing the standard requirements for fault alarms.

It is obvious that these three circuits do not interfere with each other due to the limitation of the open circuit component.

As another improvement, the structure of FIG. 4 is improved based on the structure of FIG. 2. It differs from fig. 3 in that thepower amplifier 102 does not require anoutput transformer 103. Therefore, when incorporating thedc power supply 201, anisolation inductor 211 must be added between the input terminals of the two-wire loop 104 of thepower amplifier 102. Theisolation inductor 211, on the one hand, serves as a dc path through the theoretical zero impedance, so that dc does not break down thepower amplifier 102. On the other hand, effectively isolates the node where thepower amplifier 102 inputs into the two-wire loop 104.

Further, the internal design of the wirelessfault alarm unit 204 is shown in fig. 5, and the wirelessfault alarm unit 204 is composed of a dcpower supply module 501, a Micro Control Unit (MCU)502, aload monitoring module 503, and awireless communication module 504.

Because the impedance of the two-wire loop 104 is linearly distributed, the input dc voltage of eachparallel circuit 105 is not the same. In order to ensure that thewireless alarm unit 204 can work normally, thewireless alarm unit 204 must be provided with adc power module 501 to ensure that the working voltage of thewireless alarm unit 204 is stabilized at a designed value. The most commonly used voltage is 3.3VDC or 5.0 VDC.

The Micro Control Unit (MCU)502, through its hardware functions and software programming, controls theload monitoring module 503 to continuously monitor theparallel circuit 105, matchingtransformer 106,speaker 107. The Micro Control Unit (MCU)502 also controls thewireless communication module 504 to provide communication protocol services through software programming to ensure communication with the fault information wireless collector 302 (see fig. 6).

Theload monitoring module 503 determines whether thespeaker 107 and its connection circuit are operating normally by monitoring the load of thespeaker 107. The module may be selected from an electromagnetic sensing module such as a Hall effect (Hall effect) monitoring element or other current measuring element.

Thewireless communication module 504 may select standard modules such as: IEEE802.11 series, Zigbee, bluetooth module, etc. ISM bands may also be selected for use such as: 433MHz, 902MHz and the like, and a self-defined communication protocol is matched to ensure the reliability and the stability of the faultwireless alarm unit 204. Thewireless communication module 504 is connected to theantenna 507 for providing wireless transmission function.

Fig. 6 is a schematic diagram of a two-conductor three-loop public address and fault alarm complex system. The ac and dc circuits shown in simplified form in the figure are as described above.

The third loop in the technical scheme of the invention is a control communication loop, the double-conductor loop 104 is connected with the control communication loop, the control communication loop is composed of asystem controller 301, a fault information wireless collector 302 and an antenna 303 which are connected with each other, the antenna 303 is in signal connection with anantenna 507 of a faultwireless alarm unit 204 through a wireless communication channel 304, and thesystem controller 301 is connected with thesound source 101. An effective communication protocol must exist between thesystem controller 301 and the faultywireless alarm unit 204, complying with the ISO OSI structure, to ensure that the wireless communication channel 304 is clear, so as to ensure the efficiency and reliability of the control communication loop.

Fig. 7 to 9 are another embodiment of the present invention: a double-wire fire-fighting public broadcasting system adopting a wire as a fault alarm. And simultaneously, the system provides an audio broadcasting function, a component fault wired alarm function and a direct current power supply required for completing the alarm function.

The audio broadcasting function and the dc power supply required for performing the alarm function are identical to the above-described functions and thus are not repeated here. Accordingly, fig. 7 inherits the common parts in fig. 6, and only the faultywire alarm unit 224 and the faultyinformation wire collector 310 are stated.

The design of the faulty wired alarm unit 224 (see fig. 8) is very similar to the faulty wireless alarm unit 204 (see fig. 5). The difference is that: theantenna 507 is eliminated, thewired communication module 514 replaces thewireless communication module 504, and thewired communication module 514 is externally connected with thecontacts 207 and 209.

Fig. 9 shows awired communication module 514. Control information from thetwin lead 104 enters the communicationsignal matching transformer 604 of the wiredcommunication module 514 through thecontacts 207 and 209. Amplified bylow noise amplifier 603 and passed throughhigh pass filter 602 tomodem 601. The demodulated signal is output to a Micro Control Unit (MCU) 502.

Signals (including fault alarm signals) generated by a Micro Control Unit (MCU)502 are modulated to a carrier frequency band through amodem 601, low-frequency noise is eliminated through a high-pass filter 602, and the signals are amplified by a low-noise amplifier 603 and then are merged into the double-conductor 104 through a communicationsignal matching transformer 604.

The internal design of the fault information cable collector 304 is substantially the same as the faultcable alarm unit 224. Which is identical to thetwin lead wire 104 in that one end is known to the fault wiredalarm unit 224. The other end is connected to thesystem controller 301 through a Micro Control Unit (MCU)502 by hardware and software.

The system can provide an audio broadcasting function, a component failure alarm function and a direct-current power supply required for completing the alarm function for an emergency/fire-fighting broadcast system only by applying a double-conductor loop.

With this arrangement, the audio ac circuit, the dc power supply circuit, and the wireless communication circuit can effectively coexist. And in a two-wire loop form, the dual standards of fire fighting and public broadcasting are simultaneously met.

The feasibility and the practicability of the invention are proved through specific installation and test.

The specific locations where the system is installed are the first and second floors of an enterprise office building, as shown in fig. 10 and 11.

Fig. 10 is a second floor wiring diagram. Wherein thevertical passage 401 is a wire passage that runs through the first and second floors. Thesystem core 402 is installed in a function display room on the second floor. Thesystem core 402 includes thesystem controller 301, theaudio source 101, thepower amplifier 102, thedc power supply 201, theisolation inductor 211, theisolation capacitor 202, and the like as shown in fig. 6.

The second floor fault information collector 403 (i.e., the wireless fault information collector 302 in fig. 6) is installed outside the functional display room wall. The radio frequency communication range of which can cover allspeakers 405 of the second floor. Thefault information collector 403 is connected to thesystem controller 301 in thesystem core 402 by a standard ethernet cable, complying with the TCP/IP standard communication protocol.

Thepower amplifier 102 and thedc power supply 201 in thesystem core 402 are connected to therespective speakers 405 through theisolation inductor 211 and theisolation capacitor 202 by a common two-wire 404. There are 15speakers 405 on second floor one, numbered from 1 to 15. Which are connected in parallel to thetwin lead 404.

Fig. 11 is a second floor wiring diagram. The first floorfault information collector 403 is installed in a ceiling outside the TC working area. The radio frequency communication range of which can cover all thespeakers 405 of the first floor. The first floorfault information collector 403 is connected to thesystem controller 301 in thesystem core 402 by a standard ethernet cable via avertical channel 401, complying with the TCP/IP standard communication protocol.

Thesystem core 402 is connected to atwin lead 404 that runs through avertical channel 401 to the first floor. And then connected in parallel with thefirst floor speakers 405, respectively. There are 15speakers 405 in the first floor, numbered from 16 to 30.

The official test data of the two-wire fire-fighting public broadcasting system of the embodiment are as follows:

it will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.

Claims (10)

1. A two-wire fire-fighting public broadcasting system with fault alarm comprises a sound source (101), wherein the sound source is connected with a power amplifier (102), the power amplifier (102) is connected with a two-wire loop (104), and the two-wire loop (104) is connected with a matching transformer (106) and a loudspeaker (107) through a parallel circuit (105), and is characterized in that;

an isolation capacitor (202) is inserted into a position, close to the output transformer (103), on the double-conductor loop (104), and the isolation capacitor (202) provides an alternating current signal channel for the double-conductor loop (104) and simultaneously blocks direct current from passing through to cause direct current open circuit;

the double-conductor loop (104) is connected with a direct current power supply (201), two ends of an isolation capacitor (202) are respectively connected with an anode (205) and a cathode (206) of the direct current power supply (201), and the direct current power supply (201) and the double-conductor loop (104) are connected to form a direct current loop;

a fault alarm unit and a branch isolation capacitor (203) are arranged on the parallel circuit (105);

the fault alarm unit is one of a fault wireless alarm unit (204) or a fault wired alarm unit (224);

the input end and the output end of the fault wireless alarm unit (204) are respectively connected with the primary coil of the matching transformer (106) and the two ends of the branch isolation capacitor (203);

the input end and the output end of the fault wired alarm unit (224) are respectively connected with the primary coil of the matching transformer (106) and the two ends of the branch isolation capacitor (203).

2. The two-wire fire-fighting public address system with the fault alarm function as recited in claim 1, wherein the power amplifier (102) is a class AB or C power amplifier, and the two-wire loop (104) is provided with an output transformer (103) connected with the output end of the power amplifier (102).

3. The two-wire fire-fighting public address system with the fault alarm function as recited in claim 1, wherein the power amplifier (102) is a class D power amplifier, and an isolation inductor (211) is installed between the end points of the input two-wire loop (104) of the power amplifier (102);

this isolation inductor (211) isolates the power amplifier (102) input node of the two-conductor loop (104) by passing a dc path of zero impedance so that dc does not break down the power amplifier (102).

4. The two-wire fire-fighting public broadcasting system with the fault alarm function as recited in claim 2 or 3, wherein the wireless fault alarm unit (204) or the wired fault alarm unit (224) is composed of a DC power supply module (501), a micro control unit (502), a load monitoring module (503) and a communication module;

the direct-current power supply module (501) ensures that the working voltage of the fault wireless alarm unit (204) or the fault wired alarm unit (224) is stabilized in a designed numerical range;

the micro control unit (502) controls the load monitoring module (503) to continuously monitor the parallel circuit (105), the matching transformer (106) and the loudspeaker (107);

the load monitoring module (503) judges whether the loudspeaker (107) and the connecting circuit thereof work normally by monitoring the load of the loudspeaker (107);

the communication module includes: a wireless communication module (504) and a wired communication module (514).

5. The two-wire fire-fighting public broadcasting system with the fault alarm function as recited in claim 4, wherein the two-wire loop (104) is connected with a wireless control communication loop or a wired control communication loop, the wireless communication module and the wired communication module respectively correspond to the wireless control communication loop and the wired communication control loop, the wireless control communication loop is composed of a system controller (301), a fault information wireless collector (302) and an antenna (303) which are connected with each other, the antenna (303) is in signal connection with an antenna (507) of the fault wireless alarm unit (204) through a wireless communication channel (304), and the system controller (301) is connected with the sound source (101);

the wired control communication loop is composed of a system controller (301), a signal modem (601) and a communication signal matching transformer (604) which are connected with each other.

6. The two-wire fire-fighting public address system with the fault alarm as recited in claim 1, wherein the audio source (101) is a digital audio player or an analog audio player or a real-time audio player.

7. The two-wire fire fighting public address system with a malfunction alarm according to claim 1, wherein the parallel circuit (105) is plural.

8. The two-wire fire fighting public address system with fault alarm as claimed in claim 4, wherein the load monitoring module (503) is a Hall monitoring element.

9. The two-wire fire-fighting public broadcasting system with the fault alarm function as recited in claim 4, wherein the wireless communication module (504) comprises a standard wireless communication module, the standard wireless communication module is a Zigbee module, a Bluetooth module or a Wi-Fi module, and also comprises a communication module formed by matching a customized communication protocol with an ISM frequency band, and the ISM frequency band is 433 MHz.

10. The two-wire fire-fighting public broadcasting system with fault alarm as claimed in claim 5, wherein the wired communication module (514) is connected with the two-wire control communication loop through a communication signal matching transformer (604), the communication signal generated by the micro control unit (502) is inputted into the modem (601) in the module, and after being modulated, flows into the two-wire control communication loop through the communication signal matching transformer (604), the control signal flowing from the two-wire control communication loop flows into the modem (601) of the module through the communication signal matching transformer, and the demodulated signal is inputted into the micro control unit (502).

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