Emergency broadcasting system and speaker unit

Abstract

[Problem] To make it possible to visually recognize emergency broadcast audio that is output from a speaker to residents in a coverage area of an emergency broadcast system. [Solution] The present invention comprises an emergency broadcast device 2 that can switch between any normal broadcast and an emergency broadcast that includes an emergency alert, both broadcasts being constituted by audio signals, and one or more speaker units 3 to which the audio signal is transmitted from the emergency broadcast device 2 through a speaker line 4, wherein: the speaker unit 3 includes a speaker 32 to which the audio signal of the normal broadcast and the audio signal of the emergency broadcast are input, a power receiving circuit 33 that extracts a direct-current power supply from the audio signal of the emergency broadcast, and a lighting control unit 34 that performs lighting control on a light emitting element 35 by using the direct-current power supply; and the light emitting element 35 is not lit during the normal broadcast, but is lit during then emergency broadcast.

Description

Technical Field

[0001] The present invention relates to an emergency broadcast system and a speaker unit, and more particularly, to an improvement of an emergency broadcast system that performs voice broadcasting in the event of a disaster, and an improvement of a speaker unit used in the emergency broadcast system.

Background Art

[0002] An emergency broadcast system that promotes evacuation guidance by voice broadcasting in the event of disasters such as fires and earthquakes has been conventionally known. The emergency broadcast system is configured by connecting one or two or more speakers to an emergency broadcast device that generates a voice signal. During normal times when no disaster has been detected, normal broadcasting is performed, while during emergency times when a disaster has been detected, emergency broadcasting is performed.

[0003] Normal broadcasting is voice broadcasting that includes BGM, business contact messages, etc., and emergency broadcasting is voice broadcasting that includes emergency alarms, evacuation guidance messages, etc. The emergency broadcast device switches from normal broadcasting to emergency broadcasting, for example, based on a transfer signal from an automatic fire alarm. Also, two or more speakers are installed at predetermined intervals within the coverage area of the emergency broadcast system, and emergency broadcasting can be listened to at any position within the coverage area.

[0004] Voice broadcasting is effective as an evacuation guidance method for a large number of unspecified people staying within the coverage area, but it is also conceivable that the stayers may not be able to respond to the voice broadcasting. For example, when the stayers are hearing-impaired or wearing earphones, or when the coverage area is in a noisy environment with a high volume, it is conceivable that the stayers may not notice the emergency broadcast or may notice it late. Therefore, in addition to voice broadcasting, visual notification using a light-emitting element may be used in combination to visually inform the stayers that emergency broadcasting is being performed.

[0005] In a typical emergency broadcasting system, speakers are connected to the emergency broadcasting device via speaker lines. The emergency broadcasting device operates even during a power outage by receiving power from an emergency power source, while the speakers operate solely on audio signals input via the speaker lines. Therefore, each speaker can broadcast emergency messages even during a power outage without needing its own emergency power source. However, in such an emergency broadcasting system, attempting to illuminate light-emitting elements in conjunction with emergency broadcasts would require securing a new external power source, significantly increasing costs and making implementation difficult.

[0006] Here, AV equipment and amusement equipment that link acoustic effects using speakers with optical effects using light-emitting elements have been known for some time (for example, Patent Document 1). In the invention of Patent Document 1, driving power is extracted from the audio signal of the speaker and used to control the lighting of the light-emitting elements. Therefore, as the volume of the audio signal increases, the amount of light emitted by the light-emitting elements also increases, and the amount of light emitted changes in sync with the change in volume.

[0007] The invention described in Patent Document 1 allows the light-emitting element to be illuminated without requiring a new external power source for the element. However, the invention described in Patent Document 1 relates to a gaming machine and not to an emergency broadcasting system. Furthermore, the amount of light emitted by the light-emitting element changes according to the volume, and it does not distinguish between the two types of broadcasts, normal broadcasts and emergency broadcasts, or visually indicate that an emergency broadcast is being made. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-152832 [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention has been made in view of the above circumstances, and aims to make it possible for people inside the coverage area of ​​an emergency broadcasting system to visually recognize that an emergency broadcast is being emitted from a speaker. It also aims to provide such an emergency broadcasting system at a low cost. Furthermore, it aims to provide a speaker system applicable to such an emergency broadcasting system at a low cost. [Means for solving the problem]

[0010] An emergency broadcasting system according to a first embodiment of the present invention comprises an emergency broadcasting device capable of switching between any normal broadcast and an emergency broadcast including an emergency alarm, both of which consist of voice signals, and one or more speaker units to which the voice signals are transmitted from the emergency broadcasting device via a speaker line, wherein each speaker unit comprises a speaker to which the voice signals of the normal broadcast and the voice signals of the emergency broadcast are input, a power receiving circuit that extracts DC power from the voice signals of the emergency broadcast, a power receiving circuit that extracts DC power from the voice signals of the emergency broadcast transmitted via the speaker line, and a lighting control unit that controls the lighting of a light-emitting element using the DC power, wherein the light-emitting element is configured not to light up during normal broadcasts but to light up during emergency broadcasts.

[0011] By adopting this configuration, the light-emitting elements can be illuminated without securing a new external power source. Furthermore, by having the light-emitting elements remain subdued during normal broadcasts and illuminate only during emergency broadcasts, it becomes visually clear that emergency broadcast audio is being output.

[0012] An emergency broadcasting system according to a second embodiment of the present invention, in addition to the above configuration, has a speaker line comprising a common line for transmitting a reference level, a normal signal line for transmitting audio signals for normal broadcasts, and an emergency signal line that transmits the reference level during normal broadcasts and transmits audio signals during emergency broadcasts. The speaker receives the audio signal from the normal signal line during normal broadcasts and the audio signal from the emergency signal line during emergency broadcasts. The power receiving circuit is configured to extract the DC power from the audio signal of the emergency signal line.

[0013] By adopting this configuration, it is not possible to obtain DC power during normal broadcasts, but it is possible to obtain DC power during emergency broadcasts. Therefore, the light-emitting elements do not light up during normal broadcasts, but can be lit up during emergency broadcasts. Consequently, in an emergency broadcasting system in which the speaker line consists of a common line, a normal signal line, and an emergency signal line, it is possible to visually recognize that the audio of an emergency broadcast is being output.

[0014] In addition to the above configuration, the emergency broadcasting system according to the third embodiment of the present invention is configured such that the lighting control unit determines whether or not the emergency broadcasting device is broadcasting an emergency based on the signal level of the emergency signal line, and the light-emitting element lights up in synchronization with the emergency broadcast based on the determination result.

[0015] By adopting this configuration, the light-emitting elements can be illuminated in synchronization with the emergency broadcast, making it visually possible to recognize that an emergency broadcast is being made.

[0016] In addition to the above configuration, the emergency broadcasting system according to the fourth embodiment of the present invention is configured such that the lighting control unit determines whether or not the emergency alarm is output from the emergency broadcasting device based on the signal level of the emergency signal line, and the light-emitting element lights up in synchronization with the emergency alarm based on the determination result.

[0017] By adopting this configuration, the light-emitting elements can be illuminated in synchronization with the emergency alarm, making it visually possible to recognize that an emergency alarm is sounding.

[0018] A fifth embodiment of the present invention provides an emergency broadcasting system that, in addition to the above configuration, includes an alarm determination unit that determines whether or not the emergency alarm is output from the emergency broadcasting device based on the frequency components included in the audio signal of the emergency signal line, and the light-emitting element is configured to light up in synchronization with the emergency alarm based on the determination result.

[0019] By adopting such a configuration, the light-emitting element can be lit in synchronization with the emergency alarm, making it visually recognizable that the emergency alarm is sounding. In particular, compared to the case of detecting based on a voltage level that is likely to fluctuate, the emergency alarm can be detected more reliably.

[0020] The emergency broadcast system according to the sixth embodiment of the present invention further includes a broadcast type receiving unit that receives a broadcast type signal indicating either normal broadcast or emergency broadcast from the emergency broadcast device, in addition to the above configuration. The speaker line has a pair of audio signal lines for transmitting the audio signal and a pair of type signal lines for transmitting the broadcast type signal, and the power receiving circuit is configured to generate the DC power from the audio signal on the audio signal line.

[0021] By adopting such a configuration, in an emergency broadcast system in which the speaker line is composed of a pair of audio signal lines and a pair of type signal lines, it is possible to make it visually recognizable that the audio of the emergency broadcast is being output.

[0022] The emergency broadcast system according to the seventh embodiment of the present invention further includes, in addition to the above configuration, the lighting control unit determines whether or not the audio signal is being output from the emergency broadcast device based on the signal level of the audio signal, and the light-emitting element is configured to light up in synchronization with the audio signal of the emergency broadcast.

[0023] By adopting such a configuration, the light-emitting element can be lit in synchronization with the audio signal of the emergency broadcast, making it visually recognizable that the emergency broadcast is being performed.

[0024] The emergency broadcast system according to the eighth embodiment of the present invention further includes, in addition to the above configuration, the lighting control unit determines whether or not the emergency alarm is being output from the emergency broadcast device based on the signal level of the audio signal, and the light-emitting element is configured to light up in synchronization with the emergency alarm.

[0025] By adopting such a configuration, it is possible to light the light-emitting element in synchronization with the emergency alarm and make it visually recognizable that the emergency alarm is sounding. In particular, since the emergency alarm is discriminated based on the broadcast type signal and the signal level of the audio signal, the emergency alarm can be detected with high accuracy and false detection can be prevented.

[0026] The emergency broadcast system according to the ninth embodiment of the present invention further includes an alarm discrimination unit that discriminates whether or not the emergency alarm is output from the emergency broadcast device based on the frequency components included in the audio signal, in addition to the above configuration. The light-emitting element is configured to light in synchronization with the emergency alarm based on the broadcast type signal and the result of the discrimination.

[0027] By adopting such a configuration, it is possible to light the light-emitting element in synchronization with the emergency alarm and make it visually recognizable that the emergency alarm is sounding. In particular, since the emergency alarm signal is discriminated based on the broadcast type signal and the frequency components of the audio signal, the emergency alarm can be detected with high accuracy and false detection can be prevented.

[0028] The speaker unit according to the tenth embodiment of the present invention is connected via a speaker line to an emergency broadcast device that can switch between any normal broadcast composed of an audio signal and an emergency broadcast including an emergency alarm. In the speaker unit through which the audio signal is transmitted from the emergency broadcast device, it includes a speaker to which the audio signal of the normal broadcast and the audio signal of the emergency broadcast are input, a power receiving circuit that extracts a DC power supply from the audio signal of the emergency broadcast, and a lighting control unit that controls lighting of the light-emitting element using the DC power supply. The light-emitting element is configured not to light during normal broadcast and to light during emergency broadcast.

[0029] By adopting such a configuration, it is possible to light the light-emitting element without securing a new external power supply. Also, since the light-emitting element does not light during normal broadcast and lights during emergency broadcast, it is possible to make it visually recognizable that the audio of the emergency broadcast is being output.

[0030] In addition to the above configuration, the speaker unit according to the 11th embodiment of the present invention includes, in addition to the above configuration, a power receiving circuit which comprises a rectifier circuit for rectifying the audio signal, a capacitor for smoothing the output voltage of the rectifier circuit, and a current suppression circuit for suppressing the generation of harmonics of the audio signal in the speaker line.

[0031] By adopting this configuration, the brightness of the light-emitting element can be kept constant while it is lit, and distortion of the audio signal and a decrease in the clarity of the broadcast audio can be suppressed. [Effects of the Invention]

[0032] According to the present invention, people within the coverage area of ​​an emergency broadcasting system can visually recognize that an emergency broadcast is being emitted from a speaker, thereby preventing them from noticing the emergency broadcast or noticing it too late. Furthermore, such an emergency broadcasting system can be provided at a low cost. In addition, a speaker system applicable to such an emergency broadcasting system can be provided at a low cost. [Brief explanation of the drawing]

[0033] [Figure 1] This figure shows the configuration of the emergency broadcasting system 100 according to Embodiment 1 of the present invention. [Figure 2] This diagram shows the detailed configuration of speaker unit 3 in Figure 1. [Figure 3] Figure 2 shows the detailed configuration of the power receiving circuit 33 and the lighting control unit 34. [Figure 4] This figure shows the configuration of the emergency broadcasting system 101 according to Embodiment 1 of the present invention. [Figure 5] This figure shows the configuration of an emergency broadcasting system 102 according to Embodiment 1 of the present invention. [Figure 6] Figure 5 shows the detailed configuration of the alarm discrimination unit 36. [Figure 7] This figure shows the configuration of the emergency broadcasting system 103 according to Embodiment 2 of the present invention. [Figure 8] Figure 7 shows the detailed configuration of speaker unit 3. [Figure 9] This figure shows the configuration of an emergency broadcasting system 104 according to Embodiment 2 of the present invention. [Figure 10] This figure shows the configuration of the emergency broadcasting system 105 according to Embodiment 3 of the present invention. [Figure 11] Figure 10 shows an example of the detailed configuration of speaker unit 3. [Figure 12] This figure shows one example configuration of a power receiving circuit 33 according to Embodiment 4 of the present invention. [Figure 13] This figure shows another configuration example of the power receiving circuit 33 according to Embodiment 4 of the present invention. [Figure 14] This figure shows yet another configuration example of the power receiving circuit 33 according to Embodiment 4 of the present invention. [Figure 15] This figure shows yet another configuration example of the power receiving circuit 33 according to Embodiment 4 of the present invention. [Modes for carrying out the invention]

[0034] Embodiment 1. (1) Emergency broadcasting system Figure 1 is a diagram showing an example configuration of an emergency broadcasting system according to Embodiment 1 of the present invention, illustrating the schematic configuration of the emergency broadcasting system 100. The emergency broadcasting system 100 is an in-house broadcasting system installed in the indoor space of large-scale facilities such as buildings, theaters, and airports, and comprises an emergency broadcasting device 2 that generates audio signals, one or more speaker units 3 that output audio, and a speaker line 4 that transmits audio signals from the emergency broadcasting device 2 to the speaker units 3. The emergency broadcasting device 2 is installed in the disaster prevention management room of the target facility, and the two or more speaker units 3 are distributed throughout the target facility.

[0035] The emergency broadcasting device 2 can switch between normal broadcasts and emergency broadcasts, and the speaker unit 3 controls the illumination of its light-emitting elements in synchronization with the emergency broadcast. This makes it visually possible to recognize that an emergency broadcast is being made, and can assist with voice-based evacuation guidance. For example, even people with hearing impairments or those wearing earphones can recognize that an emergency broadcast is being made. Furthermore, they can recognize that an emergency broadcast is being made even in noisy environments with high volume.

[0036] The speaker line 4 is a three-wire signal transmission means in which one or more speaker units 3 are connected in parallel, and consists of a common line 4C for the reference level, a normal signal line 4N for normal and emergency broadcasts, and an emergency signal line 4R for emergency broadcasts. During normal broadcasts, the audio signal is transmitted using the normal signal line 4N, and the emergency signal line 4R is maintained at the reference level. On the other hand, during emergency broadcasts, the audio signal is transmitted using both the emergency signal line 4R and the normal signal line 4N.

[0037] (2) Emergency broadcasting device 2 The emergency broadcasting device 2 is a device that generates audio signals for normal broadcasts or emergency broadcasts and outputs them to speaker line 4. Switching between normal broadcasts and emergency broadcasts is performed based on an alarm signal SA input from an external source.

[0038] Regular broadcasts are audio broadcasts made when no disaster is occurring, and are generally called operational broadcasts. Their content can be arbitrarily specified by the administrator. For example, they may include recorded background music and messages, or messages entered via microphone. Emergency broadcasts are audio broadcasts made when a disaster occurs, and include at least an emergency alarm, and may also include recorded messages or messages entered via microphone.

[0039] The emergency broadcasting device 2 includes an emergency broadcasting sound source 22, a source selector 23, an amplifier 24, an emergency broadcasting relay 25, input terminals 200-202, and output terminals 210-212.

[0040] Input terminals 200 to 202 receive the alarm signal SA, microphone input signal S2, and external sound source signal S3, respectively. The alarm signal SA is an external signal indicating the occurrence of a disaster such as a fire or earthquake, and is, for example, the transmission signal output by an automatic fire alarm system (not shown) when a fire is detected. The microphone input signal S2 is an audio signal output by a microphone (not shown). The external sound source signal S3 is an audio signal generated by an external sound source (not shown), and is such as background music (BGM) or messages that make up a normal broadcast.

[0041] Speaker lines 4 are connected to output terminals 210-212, and the audio signal generated by the emergency broadcasting device 2 is transmitted to one or more speaker units 3 via speaker lines 4.

[0042] The emergency broadcast sound source 22 is a sound source that generates audio signals S1 of emergency alarms and evacuation guidance messages that constitute an emergency broadcast based on the alarm signal SA. The emergency alarms and evacuation guidance messages are stored in advance, for example, as recorded audio data or audio synthesis data, and are played back as audio signals S1 when a disaster occurs. The emergency alarm is an audio signal with a predetermined frequency and variation pattern.

[0043] The source selector 23 selects one of the audio signals S1 to S3 based on the alarm signal SA and the administrator's instructions, and outputs it as the audio signal for broadcast. For example, under normal circumstances, either the microphone input signal S2 or the external sound source signal S3 is selected as the audio signal for normal broadcasts, and under emergency circumstances, either the audio signal S1 of the emergency broadcast sound source 22 or the microphone input signal S2 is selected as the audio signal for emergency broadcasts.

[0044] Amplifier 24 is an amplifier that amplifies audio signals. The amplified signal from amplifier 24 is output to the normal signal line 4N via output terminal 211.

[0045] The emergency broadcast relay 25 is a switching means that switches between normal broadcasts and emergency broadcasts based on the alarm signal SA, and selectively connects either the common line 4C or the normal signal line 4N to the emergency signal line 4R. In other words, during normal broadcasts, the emergency signal line 4R is short-circuited with the common line 4C, and the audio signal is output only to the normal signal line 4N, while during emergency broadcasts, the emergency signal line 4R is short-circuited with the normal signal line 4N, and the audio signal is output to both the normal signal line 4N and the emergency signal line 4R.

[0046] (3) Speaker unit 3 Figure 2 shows an example of the detailed configuration of the speaker unit 3 shown in Figure 1. The speaker unit 3 outputs audio based on the audio signal from the speaker line 4 and also lights up a light-emitting element in synchronization with the emergency broadcast, making it visually possible to identify that an emergency broadcast is being made. Whether or not it is an emergency broadcast is determined based on the signal level of the emergency signal line 4R. The speaker unit 3 includes input terminals 300-302, an attenuator 31, a speaker 32, a power receiving circuit 33, a lighting control unit 34, and a light-emitting element 35.

[0047] The common line 4C, normal signal line 4N, and emergency signal line 4R of speaker line 4 are connected to input terminals 300 to 302, respectively, and audio signals from the emergency broadcasting device 2 are input.

[0048] The attenuator 31 is a volume adjustment means that adjusts the volume by attenuating the audio signal. It is configured to allow volume adjustment for normal broadcasts but not for emergency broadcasts.

[0049] The attenuator 31 is a transformer-type attenuator composed of an autotransformer 310 and a volume control switch 311. The autotransformer 310 is an autotransformer that uses one coil as both the primary and secondary coil. The input terminal pair provided at both ends of the coil is connected to the normal signal line 4N and the emergency signal line 4R, and one or more output taps provided on the coil are used as output terminals. The volume control switch 311 selects one of the output taps according to user operation and supplies the audio signal of the selected output tap to the speaker 32. During normal broadcasting, the primary terminal pair of the autotransformer 310 receives the normal broadcast audio signal and the reference level, respectively. Therefore, the volume can be adjusted by operating the volume control switch 311 to select an output tap. On the other hand, during emergency broadcasting, both primary terminal pairs of the autotransformer 310 receive the emergency broadcast audio signal. Therefore, regardless of the output tap selected by the volume control switch 311, the emergency broadcast audio signal is output to the speaker 32 without being attenuated by the attenuator 31.

[0050] Speaker 32 is a device that converts the audio signal output from attenuator 31 into sound waves and emits them into space.

[0051] The power receiving circuit 33 is a circuit that extracts power from the audio signal. The power receiving circuit 33 is connected to the emergency signal line 4R, rectifies the audio signal of the emergency broadcast to generate a DC voltage, and supplies it to the lighting control unit 34. The emergency signal line 4R maintains a reference level during normal broadcasts, but transmits the audio signal during emergency broadcasts, so the power receiving circuit 33 can extract power only during emergency broadcasts.

[0052] The lighting control unit 34 is a constant current circuit that supplies a constant current to the light-emitting element 35 based on the DC power supply provided by the power receiving circuit 33. The light-emitting element 35 is a light-emitting means that lights up with the current supplied by the lighting control unit 34, and can be an LED, for example.

[0053] The output voltage of the power receiving circuit 33 changes according to the signal level of the audio signal, that is, the volume of the audio signal. The lighting control unit 34 supplies power to the light-emitting element 35 only when the input voltage from the power receiving circuit 33 exceeds a predetermined threshold voltage Vth. In other words, if the input voltage is below the threshold voltage Vth, no current is supplied to the light-emitting element 35, and if it exceeds the threshold voltage Vth, a predetermined current is supplied.

[0054] Therefore, by setting the threshold voltage Vth to an appropriate value, the light-emitting element 35 can be lit in synchronization with the audio signal of the emergency broadcast. In other words, the lighting control unit 34 determines whether or not an audio signal of the emergency broadcast is being input based on the volume of the audio signal on the emergency signal line 4R, and lights up the light-emitting element 35 based on this determination result.

[0055] For example, by setting the threshold voltage Vth to a relatively small value, the light-emitting element 35 can be lit in synchronization with all audio signals that make up an emergency broadcast, including emergency alarms and evacuation guidance messages.

[0056] Furthermore, by setting the threshold voltage Vth to a relatively large value, the light-emitting element 35 can be illuminated only in synchronization with emergency alarms. Typically, emergency broadcasts include emergency alarms, which are louder than other content such as evacuation guidance messages. Therefore, by setting the threshold voltage Vth to an appropriate value, the light-emitting element 35 can be illuminated only when an emergency alarm is output.

[0057] When the lighting control unit 34 lights up the light-emitting element 35, it supplies a predetermined constant current to the light-emitting element 35. This allows the light-emitting element 35 to light up at a constant brightness, clearly indicating that an emergency broadcast is being made.

[0058] Figure 3 shows an example of the detailed configuration of the power receiving circuit 33 and the lighting control unit 34 shown in Figure 2. The power receiving circuit 33 includes a bridge circuit BR composed of diodes D1 to D4 and a capacitor C1 connected in parallel to the output terminal of the bridge circuit BR.

[0059] The bridge circuit BR is a rectifier circuit that full-wave rectifies the audio signal. When the audio signal from the emergency signal line 4R is input to the power receiving circuit 33, it is rectified by the bridge circuit BR and smoothed by the capacitor C1 to generate a DC voltage Vd. The generated DC voltage Vd is input to the lighting control unit 33.

[0060] The lighting control unit 34 is a constant current circuit composed of NPN transistors Q1 and Q2 and resistors R1 and R2. Transistor Q1 forms an emitter follower circuit, and resistors R1 and R2 and a light-emitting element 35 are connected to its base, emitter, and collector terminals, respectively. The collector current supplied to the light-emitting element 35 is determined by the base current flowing through resistor R1 and the current amplification factor of transistor Q1.

[0061] Transistor Q2 forms a common-emitter circuit, with its collector and base terminals connected to the base and emitter terminals of transistor Q1, respectively. Transistor Q2 turns on due to the voltage drop across resistor R2 and defines the base current of transistor Q1. Therefore, a predetermined constant current can be supplied to the light-emitting element 35. Furthermore, the power supply voltage Vd required to supply a constant current to the light-emitting element 35, i.e., the voltage threshold Vth, is determined by resistors R1 and R2.

[0062] In the emergency broadcasting system 100 according to this embodiment, the light-emitting element 35 can be illuminated by drawing power from the audio signal, without having to secure an external power source. Furthermore, by drawing power from the audio signal of the emergency signal line 4R, the light-emitting element 35 can be illuminated in synchronization with the audio signal of the emergency broadcast. In addition, by determining whether an emergency alarm has occurred based on the volume of the audio signal of the emergency signal line 4R, the light-emitting element 35 can also be illuminated in synchronization with the emergency alarm.

[0063] (4) Other configuration example 1 Figure 4 is a diagram showing another configuration example of an emergency broadcasting system according to Embodiment 1 of the present invention, and shows emergency broadcasting system 101. Emergency broadcasting system 101 differs from emergency broadcasting system 100 (Figure 2) in that the speaker unit 3 consists of an attenuator 31 and a speaker device 5, and the speaker device 5 is connected to the speaker line 4 via the attenuator 31.

[0064] The speaker device 5 comprises a speaker 32, a power receiving circuit 33, a lighting control unit 34, and a light-emitting element 35, and by connecting the attenuator 31, it has the same configuration as the speaker unit 3 (Figure 2) of the emergency broadcasting system 100. The speaker device 5 and the attenuator 31 are located close to each other. For example, the speaker device 5 and the attenuator 31 are installed in the same room, with the speaker device 5 installed on the ceiling and the attenuator 31 on the wall.

[0065] In other words, the speaker unit 3 may be configured as a single unit with each component 31 to 35 housed in the same enclosure, but any component may be separable as long as they are located in close proximity and connected to one another.

[0066] (5) Other configuration example 2 Figures 5 and 6 show yet another configuration example of the emergency broadcasting system according to Embodiment 1 of the present invention. Figure 5 shows the emergency broadcasting system 102, and Figure 6 shows the detailed configuration of the alarm discrimination unit 36 ​​in Figure 5. The speaker unit 3 constituting the emergency broadcasting system 102 differs from the speaker unit 3 of the emergency broadcasting system 100 (Figure 2) in that it has an alarm discrimination unit 36.

[0067] The alarm discrimination unit 36 ​​is a means for determining whether an emergency alarm is present based on the frequency components contained in the audio signal, and operates using power supplied from the power receiving circuit 33. The alarm discrimination unit 36 ​​is connected to the emergency signal line 4R and receives the audio signal of an emergency broadcast. By detecting whether or not the audio signal contains predetermined emergency alarm frequency components, it is possible to determine whether or not the audio signal is an emergency alarm.

[0068] The alarm determination unit 36 ​​includes one or more tone detection units 360 to 362 and a signal determination unit 363. The tone detection units 360 to 362 are circuits that detect (tone detection) whether or not a voice signal contains different predetermined frequency components. The signal determination unit 363 determines whether or not the input voice signal is an emergency alarm based on the detection results of the tone detection units 360 to 362. The emergency alarm determination result is output to the lighting control unit 34.

[0069] Generally, emergency alarms consist of frequency signals with a single frequency component. For example, tone alarms that sequentially output two or more different frequency signals at regular intervals, or sweep alarms that output frequency signals while sweeping from the first frequency to the second frequency are used. Therefore, an emergency alarm can be detected by detecting that a frequency specific to emergency alarms is included in the audio signal.

[0070] For example, in the case of a tone alarm that alternates between 740Hz and 494Hz for 0.5 seconds each, an emergency alarm can be detected with high accuracy by detecting the 740Hz and 494Hz frequency components separately. Alternatively, it is possible to detect only one of the frequencies and consider it detected for the duration of the repeating cycle.

[0071] Furthermore, in the case of a sweep signal that sweeps the frequency from 300Hz to 2kHz in 0.5 seconds, by detecting the 300Hz and 2kHz frequency components respectively, it is possible to detect the emergency alarm with high accuracy and prevent false detections. Alternatively, it is also possible to detect only the frequency component at the start of the sweep (300Hz) and consider it as detected for the duration of the sweep.

[0072] The lighting control unit 34 drives the light-emitting element 35 based on the result of the emergency alarm detection. Therefore, the light-emitting element 35 can be illuminated in synchronization with the emergency alarm.

[0073] By identifying emergency alarms using tone detection, it is possible to identify emergency alarms with higher accuracy compared to identifying them by volume. Furthermore, by performing tone detection on the audio signal of emergency broadcasts, it is possible to suppress the occurrence of false detections compared to performing tone detection on the audio signal of normal broadcasts, which may include background music.

[0074] Embodiment 2. In Embodiment 1, examples of emergency broadcasting systems 100-102 using a 3-wire speaker line 4 were described. In this embodiment, however, emergency broadcasting systems 103 and 104 using a 4-wire speaker line 4 will be described.

[0075] Figure 7 shows an example configuration of an emergency broadcasting system according to Embodiment 2 of the present invention, and shows the emergency broadcasting system 103. In the emergency broadcasting system 103, one or more speaker units 3 are connected to the emergency broadcasting device 2 via a 4-wire speaker line 4.

[0076] Speaker line 4 consists of a common line 4C, a normal signal line 4N, and a pair of type signal lines 4a and 4b. Compared to speaker line 4 of the emergency broadcasting system 100 (Embodiment 1), it differs in that it has a pair of type signal lines 4a and 4b instead of an emergency signal line 4R. The pair of type signal lines 4a and 4b transmit broadcast type signals that indicate the operating status of the emergency broadcasting device 2. The broadcast type signal is a signal that indicates whether the current broadcasting state is normal broadcasting or emergency broadcasting.

[0077] The emergency broadcasting device 2 includes input terminals 200-202, output terminals 210, 211, 213, 214, an emergency broadcasting sound source 22, a source selector 23, an amplifier 24, and a broadcast type transmitting unit 26. Compared to the emergency broadcasting system 100 (Embodiment 1), it differs in that it has a broadcast type transmitting unit 26 instead of an emergency broadcasting relay 25. The amplified signal from the amplifier 24 is output to the normal signal line 4N via output terminal 211. The broadcast type transmitting unit 26 outputs a broadcast type signal to the type signal lines 4a and 4b based on the alarm signal SA. For example, by associating normal broadcasts and emergency broadcasts with voltage levels of 24V and 0V, respectively, and controlling the voltage between the pair of type signal lines 4a and 4b to 24V or 0V, the broadcast type signal is transmitted.

[0078] Figure 8 shows an example of the detailed configuration of the speaker unit 3 shown in Figure 7. The speaker unit 3 consists of an attenuator 31 and a speaker device 5. The attenuator 31 consists of an autotransformer 310, a volume control switch 311, and a deactivation relay 312.

[0079] The input terminal pair provided at both ends of the coil of the autotransformer 310 is normally connected to the signal line 4N and the common line 4C. One end of the coil is connected to the speaker 32, and one or more output taps are provided, all of which are connected to the volume control switch 311. The volume control switch 311 selects one of the two or more output taps according to user operation, and the selected output tap is connected to the speaker 32 via the deactivation relay 312.

[0080] The deactivation relay 312 is a switching means that switches based on the broadcast type signal and deactivates volume control during emergency broadcasts. If the broadcast type signal indicates a normal broadcast, the deactivation relay 312 inputs the output of the volume control switch 311 to the speaker 32 and attenuates the audio signal according to user operation. However, if it indicates an emergency broadcast, it connects the other end of the secondary coil to the speaker 32 and inputs the audio signal to the speaker 32 without attenuation.

[0081] The broadcast type receiving unit 37 receives broadcast type signals from type signal lines 4a and 4b and is a means for determining whether or not it is an emergency broadcast. If it is an emergency broadcast, it outputs a lighting control signal to the lighting control unit 34 to light up the light-emitting element 35.

[0082] The power receiving circuit 33 is a circuit that extracts power from the audio signal. The power receiving circuit 33 is connected to the audio signal output terminal of the attenuator 31, rectifies the audio signal input to the speaker 32 to generate a DC voltage, and supplies it to the lighting control unit 34. Since the attenuator 31 disables the volume control switch 311 during emergency broadcasts, the power receiving circuit 33 can generate power from an audio signal that has not been volume-adjusted during emergency broadcasts. The power receiving circuit 33 can also be connected to the normal signal line 4N before the autotransformer 310.

[0083] The lighting control unit 34 lights up the light-emitting element 35 during an emergency broadcast based on the broadcast type receiving unit 37's determination result. The lighting control unit 34 is a constant current circuit that supplies a constant current to the light-emitting element 35, causing it to light up at a constant brightness. The lighting control unit 34 also supplies power to the light-emitting element 35 when the output voltage of the power receiving circuit 33 exceeds a predetermined threshold voltage Vth. Therefore, the lighting of the light-emitting element 35 is performed based on the broadcast type determination result and the signal level of the audio signal.

[0084] For example, the lighting control unit 34 can be configured to supply power to the light-emitting element 35 when the output voltage of the power receiving circuit 33 exceeds a relatively small threshold voltage Vth. In this case, power is supplied to the light-emitting element 35 not only when the audio signal is an emergency alarm, but also when the content is quieter, such as an evacuation guidance message. Therefore, the light-emitting element 35 can be lit in synchronization with the audio signal of an emergency broadcast.

[0085] On the other hand, the lighting control unit 34 can also be configured to supply power to the light-emitting element 35 when the output voltage of the power receiving circuit 33 exceeds a relatively large threshold voltage Vth. In this case, power is supplied to the light-emitting element 35 only when the audio signal is an emergency alarm. Therefore, the light-emitting element 35 can be illuminated in synchronization with the emergency alarm.

[0086] In this embodiment, the light-emitting element 35 can be illuminated by drawing power from the audio signal, without needing to secure an external power source. Furthermore, by determining whether or not it is an emergency broadcast based on the broadcast type signal received via the type signal lines 4a and 4b, the light-emitting element 35 can be illuminated during an emergency broadcast. In addition, by supplying a constant current to the light-emitting element to cause it to emit light, the light-emitting element 35 can be illuminated at a constant brightness.

[0087] Figure 9 shows another configuration example of an emergency broadcasting system according to Embodiment 2 of the present invention, and shows an emergency broadcasting system 104. The emergency broadcasting system 104 differs from the emergency broadcasting system 103 (Figure 8) in that the speaker unit 3 further includes an alarm discrimination unit 36.

[0088] The alarm discrimination unit 36 ​​is a means for discriminating an emergency alarm by tone detection and operates on power supplied from the power receiving circuit 33. The internal configuration of the alarm discrimination unit 36 ​​is the same as in the case of the emergency broadcasting system 102 (Figure 5). The alarm discrimination unit 36 ​​is connected to the audio signal output terminal of the attenuator 31 and receives the audio signal that is input to the speaker 32. By detecting whether or not the audio signal contains predetermined emergency alarm frequency components, it is possible to determine whether or not the audio signal is an emergency alarm.

[0089] The lighting control unit 34 lights up the light-emitting element 35 in synchronization with the emergency alarm, based on the determination result of the broadcast type receiving unit 37 and the determination result of the alarm determination unit 36. In other words, the light-emitting element 35 is lit when it is determined to be an emergency broadcast based on the broadcast type signal and when it is determined to be an emergency alarm based on tone detection. Therefore, it is possible to determine emergency alarms with high accuracy and light up the light-emitting element 35 in synchronization with the emergency alarm. In addition, the lighting control unit 34 is a constant current circuit that supplies a constant current to the light-emitting element 35, so that the light-emitting element 35 can be lit at a constant brightness when an emergency alarm is output.

[0090] Embodiment 3. Embodiments 1 and 2 described examples of emergency broadcasting systems 100 to 104 using three-wire or four-wire speaker lines 4. In contrast, this embodiment describes an emergency broadcasting system 105 using two-wire speaker lines 4.

[0091] Figure 10 shows an example configuration of an emergency broadcasting system according to Embodiment 3 of the present invention, and shows the emergency broadcasting system 105. In the emergency broadcasting system 105, one or more speaker units 3 are connected to the emergency broadcasting device 2 via a two-wire speaker line 4.

[0092] Speaker line 4 consists of a common line 4C and a normal signal line 4N. Compared to speaker line 4 of the emergency broadcasting system 100 (Figure 1), it differs in that it does not have an emergency signal line 4R.

[0093] The emergency broadcasting device 2 switches between normal broadcasting and emergency broadcasting based on the alarm signal SA, and selectively generates either the normal broadcasting audio signal or the emergency broadcasting audio signal. However, it does not have an emergency broadcasting relay 25, and both the emergency broadcast and the emergency broadcasting audio signal are transmitted to each speaker unit 3 via the normal signal line 4N.

[0094] Figure 11 shows an example of the detailed configuration of speaker unit 3 shown in Figure 10. Speaker unit 3 does not have an attenuator 31, and the audio signal received via the normal signal line 4N is input directly to speaker 32. In other words, the audio signals for normal broadcasts and emergency broadcasts are input to speaker 32 without distinction.

[0095] The power receiving circuit 33 is a circuit that extracts power from the audio signal. The power receiving circuit 33 is normally connected to the signal line 4N, rectifies the audio signal to generate a DC voltage, and supplies it to the lighting control unit 34 and the alarm discrimination unit 36.

[0096] The alarm discrimination unit 36 ​​is a means for discriminating an emergency alarm by tone detection and operates on power supplied from the power receiving circuit 33. The alarm discrimination unit 36 ​​is normally connected to the signal line 4N and determines whether an audio signal is an emergency alarm by detecting whether or not the audio signal contains a predetermined emergency alarm frequency component. The discrimination result of the alarm discrimination unit 36 ​​is output to the lighting control unit 34.

[0097] The lighting control unit 34 drives the light-emitting element 35 based on the result of the emergency alarm detection. Therefore, the light-emitting element 35 can be illuminated in synchronization with the emergency alarm.

[0098] Embodiment 4. In this embodiment, other configuration examples of the power receiving circuit 33 shown in Figure 2 will be described. In particular, a configuration of the power receiving circuit 33 that suppresses distortion in broadcast audio caused by the nonlinearity of the power receiving circuit 33 and the lighting control circuit 34 will be described.

[0099] Due to the nonlinearity of the load circuits, such as the power receiving circuit 33 and the lighting control unit 34, the current change flowing from the speaker line 4 to the speaker unit 3 is nonlinear with respect to voltage changes. Since the speaker line 4 has line resistance, such nonlinear current changes cause a nonlinear voltage drop, resulting in a distortion voltage appearing in the speaker line 4. In particular, if the line resistance of the speaker line 4 is large, the distortion voltage will also be large, leading to distortion of the audio signal input to the speaker unit 3, which negatively affects the clarity of the sound.

[0100] Generally, emergency broadcasting systems are configured by connecting numerous speaker units 3 to a speaker line 4. Therefore, the speaker line 4 is laid over long distances, for example, 500m to 1000m, and its line resistance is expected to be relatively high, for example, several tens of ohms.

[0101] Distortion voltage specifically occurs as harmonics relative to the fundamental frequency of the audio signal, either steadily or transiently. If the line resistance of speaker line 4 is high, the harmonics will also be high. Generally, in the case of audio signals, distortion relative to the fundamental frequency—for example, the sum of all harmonics and other noise—is considered perceptible and unpleasant if it exceeds 1%.

[0102] Therefore, by providing a current suppression circuit between the speaker line 4 and the bridge circuit BR, the generation of distortion voltage can be suppressed. The current suppression circuit suppresses current input from the speaker line 4, suppresses the current that flows when charge accumulates in the capacitor C1, and softens the switching operation of the nonlinear portion of the rectifier circuit BR, thereby suppressing current distortion.

[0103] A current suppression circuit can be composed of passive elements such as inductors, resistors, or a combination thereof. Alternatively, the current suppression circuit may be one in which the current increases proportionally up to a predetermined input voltage, then decreases proportionally for voltages above that voltage, until the current reaches a minimum (e.g., 0A) by the time the rated voltage is reached. Furthermore, the current suppression circuit may be one in which the load remains constant up to a predetermined input voltage, but the load resistance increases proportionally for voltages above that voltage. Finally, the current suppression circuit may be one in which the load remains constant up to a predetermined input voltage, but becomes a constant current for voltages above that voltage.

[0104] Figure 12 shows one example configuration of the power receiving circuit 33 according to Embodiment 4 of the present invention, and illustrates another example configuration of the power receiving circuit 33 shown in Figure 2. This power receiving circuit 33 differs from the power receiving circuit 33 (Embodiment 1) in that it includes a current suppression circuit 38.

[0105] The current suppression circuit 38 consists of an inductor L1 and a resistor R3. The inductor L1 is provided at one of the input terminals of the bridge circuit BR, and the resistor R3 is provided at the other. In the figure, the inductor L1 is provided at the input terminal connected to the emergency signal line 4R, and the resistor R3 is provided at the input terminal connected to the common line 4C, but the inductor L1 and resistor R3 can also be swapped.

[0106] Since inductor L1 has the property of being less conductive to current as the frequency increases, the current suppression circuit 38 functions as a filter circuit that suppresses harmonic currents flowing in from speaker line 4, thereby suppressing the generation of distortion voltage.

[0107] The greater the degree to which the current suppression circuit 38 suppresses the current, the more the generation of harmonics is suppressed, but the longer the time it takes for charge to accumulate in the capacitor C1, the worse the responsiveness of the light-emitting element 35 when it lights up. Considering the responsiveness and the clarity of the sound, it is desirable to adjust the current suppression circuit 38 to a range where harmonic distortion does not cause audible problems, for example, so that the voltage of the distortion component is less than 1% of the fundamental frequency.

[0108] Figure 13 shows another configuration example of the power receiving circuit 33 according to Embodiment 4 of the present invention, and is an alternative configuration example of the power receiving circuit 33 (Embodiment 1) shown in Figure 2. This power receiving circuit 33 differs from the power receiving circuit 33 in Figure 12 in that it has a single diode D5 instead of a bridge circuit BR, and performs half-wave rectification together with a capacitor C1. By adopting such a configuration, a DC power supply can be obtained with a simple circuit configuration.

[0109] When the power receiving circuit 33 is half-wave rectified, as shown in Figure 14, it is desirable that a pair of power receiving circuits 33, 33' connected to two lighting control units 34 share a single current suppression circuit 38 and are connected in opposite phases to each other. The pair of power receiving circuits 33, 33' can be provided in the same speaker unit 3, or they can be provided in separate speaker units 3. In the latter case, the two speaker units 3 form a pair of speaker units.

[0110] Figure 15 shows yet another configuration example of the power receiving circuit 33 according to Embodiment 4 of the present invention, and is an example of another configuration of the power receiving circuit 33 (Embodiment 1) shown in Figure 2. This power receiving circuit 33 differs from the power receiving circuit 33 in Figure 12 in that it includes two diodes D6 and D7 and two capacitors C2 and C3 instead of the bridge circuit BR and capacitor C1.

[0111] Diode D6 and capacitor C2 perform half-wave rectification when the sign of the AC voltage of the audio signal is positive, while diode D7 and capacitor C3 perform half-wave rectification when the sign of the AC voltage of the audio signal is negative. In other words, diodes D6, D7 and capacitors C2, C3 constitute a voltage doubler rectifier circuit. A DC power supply can also be obtained by adopting this configuration.

[0112] The current suppression circuit 38 is provided with a series circuit of inductor L2 and resistor R4 on one of the input terminals of the power receiving circuit 33, and a series circuit of inductor L3 and resistor R5 on the other.

[0113] Furthermore, by providing insulation between the speaker line 4 and the power receiving circuit 33 using a transformer, it is possible to prevent people from touching the light-emitting element 35 and other components and suffering electric shock. While it is not usually expected that people will directly touch the speaker wiring or the speaker's voice coil itself, it is conceivable that people may come into contact with the light-emitting element 35 and other components. [Explanation of Symbols]

[0114] 100-105 Emergency Broadcast System 2. Emergency broadcasting system 200~202 Input terminals 210-213 Output terminals 22 Emergency broadcast sound source 23 Source Selector 24 Amplifier 25 Emergency broadcast relay 26 Broadcast Type Transmission Section 3 Speaker Units 300~302 Input terminals 31 Attenuator 310 Autotransformer 311 Volume control switch 312 Disabled Relay 32 speakers 33 Power receiving circuit 34 Lighting control unit 35 Light-emitting element 36 Alarm discrimination section 360~362 Tone detection unit 363 Signal determination unit 37 Broadcast type receiving unit 38 Current suppression circuit 4 speaker lines 4C Common Line 4N Standard signal line 4R Emergency signal line 4a, 4b Type signal lines 5. Speaker device SA alarm signal S1 Audio signal S2 Microphone Input Signal S3 External audio signal BR bridge circuit C1~C3 Capacitors D1~D7 Diodes L1~L3 Inductors Q1, Q2 Transistors R1~R5 Resistors Vd DC voltage

Claims

1. Both are emergency broadcasting devices that can switch between any normal broadcast consisting of audio signals and emergency broadcasts including emergency alarms, The system comprises one or more speaker units through which the audio signal is transmitted from the emergency broadcasting device via a speaker line, The aforementioned speaker unit, A speaker into which the audio signals for the regular broadcast and the emergency broadcast are input, A power receiving circuit that extracts DC power from the audio signal only when an emergency broadcast is being made by the emergency broadcasting device, The system includes a lighting control unit that controls the lighting of the light-emitting element using the DC power supply, The power receiving circuit has a current suppression circuit at its input terminal to suppress the generation of harmonics of the audio signal in the speaker line. The aforementioned light-emitting element is characterized in that it does not light up during normal broadcasts but lights up during emergency broadcasts.

2. The speaker line comprises a common line for transmitting a reference level, a normal signal line for transmitting audio signals for normal broadcasts, and an emergency signal line that transmits the reference level during normal broadcasts and transmits audio signals only during emergency broadcasts. The aforementioned speaker receives audio signals from the normal signal line during normal broadcasts, and audio signals from the emergency signal line during emergency broadcasts. The emergency broadcasting system according to claim 1, characterized in that the power receiving circuit extracts the DC power from the audio signal transmitted only to the emergency signal line.

3. An emergency broadcasting device that can switch between any normal broadcast consisting of an audio signal and an emergency broadcast including an emergency alarm, The system comprises one or more speaker units through which the audio signal is transmitted from the emergency broadcasting device via a speaker line, The aforementioned speaker unit, A speaker into which the audio signals for the regular broadcast and the emergency broadcast are input, A power receiving circuit that extracts DC power from the audio signal only when an emergency broadcast is being made by the emergency broadcasting device, A lighting control unit that controls the lighting of the light-emitting element using the DC power supply, The system includes an alarm determination unit that determines whether or not the emergency alarm is being output from the emergency broadcasting device based on the frequency components contained in the audio signal of the speaker line, The lighting control unit determines whether or not the emergency broadcasting device is broadcasting the emergency based on the signal level of the speaker line and the determination result of the alarm determination unit. The light-emitting element is characterized in that, based on the determination result of the lighting control unit, it does not light up during normal broadcasts but lights up during emergency broadcasts.

4. An emergency broadcasting device that can switch between any normal broadcast consisting of an audio signal and an emergency broadcast including an emergency alarm, The system comprises one or more speaker units through which the audio signal is transmitted from the emergency broadcasting device via a speaker line, The aforementioned speaker unit, A speaker into which the audio signals for the regular broadcast and the emergency broadcast are input, A power receiving circuit that extracts DC power from the audio signal only when an emergency broadcast is being made by the emergency broadcasting device, A lighting control unit that controls the lighting of the light-emitting element using the DC power supply, The system includes an alarm determination unit that determines whether or not the emergency alarm is being output from the emergency broadcasting device based on the frequency components contained in the audio signal of the speaker line, The lighting control unit determines whether or not the emergency alarm is being output from the emergency broadcasting device based on the signal level of the speaker line and the determination result of the alarm determination unit. The light-emitting element is characterized in that, based on the determination result of the lighting control unit, it does not light up when the emergency alarm is not output, and lights up when the emergency alarm is output.

5. The system includes an alarm determination unit that determines whether or not the emergency alarm is being output from the emergency broadcasting device based on the frequency components contained in the audio signal of the speaker line. The emergency broadcasting system according to claim 1, characterized in that the light-emitting element lights up in synchronization with the emergency alarm based on the determination result.

6. The system includes a broadcast type receiving unit that receives a broadcast type signal indicating either a regular broadcast or an emergency broadcast from the emergency broadcasting device, The speaker line has a pair of audio signal lines for transmitting the audio signal and a pair of type signal lines for transmitting the broadcast type signal. The emergency broadcasting system according to claim 1, characterized in that the power receiving circuit generates the DC power supply from the audio signal of the audio signal line.

7. The lighting control unit determines whether or not the audio signal is being output from the emergency broadcasting device based on the signal level of the audio signal. The emergency broadcasting system according to claim 6, characterized in that the light-emitting element lights up in synchronization with the audio signal of the emergency broadcast.

8. The lighting control unit determines, based on the signal level of the audio signal, whether or not the emergency alarm is being output from the emergency broadcasting device. The emergency broadcasting system according to claim 6, characterized in that the light-emitting element lights up in synchronization with the emergency alarm.

9. The system includes an alarm determination unit that determines whether or not the emergency alarm is being output from the emergency broadcasting device based on the frequency components contained in the audio signal. The emergency broadcasting system according to claim 6, characterized in that the light-emitting element lights up in synchronization with the emergency alarm based on the broadcast type signal and the result of the determination.

10. In an emergency broadcasting device that can switch between any normal broadcast consisting of audio signals and an emergency broadcast including an emergency alarm, a speaker unit is connected via a speaker line and receives the audio signals from the emergency broadcasting device. A speaker into which the audio signals for the regular broadcast and the emergency broadcast are input, A power receiving circuit that extracts DC power from the audio signal only when an emergency broadcast is being made by the emergency broadcasting device, The system includes a lighting control unit that controls the lighting of the light-emitting element using the DC power supply, The power receiving circuit has a current suppression circuit at its input terminal to suppress the generation of harmonics of the audio signal in the speaker line. The speaker unit is characterized in that the light-emitting element does not light up during normal broadcasts but lights up during emergency broadcasts.

11. The aforementioned power receiving circuit is A rectifier circuit for rectifying the aforementioned audio signal, The rectifier circuit has a capacitance that smooths the output voltage, The speaker unit according to claim 10, characterized in that the current suppression circuit is provided between the speaker line and the rectifier circuit.

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