JP4493564B2 - Speaker line inspection device and terminal device for speaker line inspection device - Google Patents

Description

  The present invention relates to a speaker line inspection device that inspects whether a speaker line is disconnected or short-circuited, and a terminal device used in the inspection device.

  The speaker line is composed of two lines. In a building such as a building, the speaker line is laid in each room, an amplifier is connected to one end thereof, and a speaker is connected between both lines in each room. An example of an inspection apparatus for inspecting the speaker line is disclosed in Patent Document 1.

In the inspection apparatus of Patent Document 1, the output transformer of the amplifier has two secondary windings, and these two secondary windings are connected in series with a capacitor. One end of the secondary winding to which the capacitor is not connected is connected to one terminal of the speaker via the first speaker line, and the other end of the secondary winding to which the capacitor is not connected is the second end. It is connected to the other terminal of the speaker via the speaker line. A DC power source, a resistor, and a photocoupler are connected in series between both ends of the capacitor. If the first and second speaker lines are not disconnected, the current from the DC power source is the resistor, one secondary winding, the first speaker line, the speaker, the second speaker line, and the other two. The current flows to the DC power source through the next winding and the photocoupler, and the photocoupler operates. On the other hand, when one of the first and second speaker lines is disconnected, no current flows and the photocoupler does not operate. Therefore, it is possible to detect the presence or absence of disconnection. Since the two secondary windings are connected in series by the capacitor, the AC signals induced in the secondary windings are added by the capacitor and supplied to the speaker.

JP-A-6-242172

  In this inspection apparatus, it is necessary to connect two secondary windings with a capacitor, which increases the cost. In particular, when a plurality of speakers are connected between the first and second speaker lines, the first and second speakers and capacitors are connected in series to prevent direct current from flowing through each speaker. A connection must be made between the second speaker lines, which further increases the cost. In addition, when the first and second speaker lines are short-circuited, a short circuit cannot be detected because a current flows through the photocoupler.

  It is an object of the present invention to provide a speaker line inspection apparatus that can detect not only a disconnection but also a short circuit at low cost.

In the speaker line inspection apparatus of one aspect of the present invention, a speaker is connected between the first and second speaker lines whose starting ends are respectively connected to the two output terminals of the power amplifier. A plurality of speakers may be connected between the first and second speaker lines. When an AC signal is detected at the terminal located away from the starting ends of the first and second speaker lines, the impedance connecting means has an impedance having a predetermined impedance between the terminal of the second speaker line and the common potential point. Connect the elements. As the AC signal, for example, a reference AC signal having an inaudible frequency can be used, and this reference AC signal may be continuously supplied to the first and second speaker lines. This AC signal can be supplied to the input terminal of the power amplifier, or can be supplied between the start ends of the first and second speaker lines. As the impedance element, for example, a resistor can be used alone, or a capacitor, a combination of a capacitor and a resistor, or a combination of a capacitor, a coil, and a resistor can be used. The first determination means determines whether or not the impedance between the starting end of the second speaker line and the common potential point is a predetermined impedance.

  In the speaker line inspection apparatus configured as described above, when no disconnection or short-circuit occurs in the first and second speaker lines, an AC signal is transmitted to the ends of the first and second speaker lines and is transmitted by the impedance connecting means. Detected. As a result, the impedance element is connected between the second speaker line and the common potential point. If a break occurs in the first or second speaker line, or if a short circuit occurs between the first and second speaker lines, an AC signal is not detected at the ends of the first and second speaker lines, and the impedance element Are not connected between the second speaker line and the common potential point. Therefore, the first determination means measures the impedance between the starting end of the second speaker line and the common potential point, and if the impedance is larger than a predetermined impedance, a short circuit occurs between the first and second speaker lines. However, it can be determined that a disconnection has occurred in the first or second speaker line. In this configuration, the impedance between the second speaker line and the common potential point is measured, and the impedance is not measured between the first and second speaker lines. Therefore, it is not necessary to pass a direct current through the first and second speaker lines for impedance measurement, and it is not necessary to connect the speaker and the capacitor in series and connect between the first and second speaker lines. Cost can be reduced. Moreover, not only disconnection but also short circuit can be detected.

  The first determination unit may have a DC power source. One terminal of the DC power supply is connected to the common potential point, and the other electrode is connected to the starting end of the second speaker line via another impedance element. The comparison means compares the voltage between the starting end of the second speaker line and the common potential point with a reference voltage predetermined for the common potential point.

  When an impedance element is connected between the second speaker line and the common potential point, the voltage between the start end of the second speaker line and the common potential point is a predetermined voltage. When an impedance element is not connected between the second speaker line and the common potential point, the voltage between the starting end of the second speaker line and the common potential point is higher than a predetermined voltage. Therefore, whether the impedance element is connected between the second speaker line and the common potential point by comparing the voltage between the starting end of the second speaker line and the common potential point with a predetermined voltage. As a result, it can be determined whether the first or second speaker line is disconnected or whether the first and second speaker lines are short-circuited. Also in this case, as described above, the current from the DC power source flows between the second speaker line and the common potential point, and does not flow to the first and second speaker lines. There is no need to connect a series circuit between the first and second speaker lines.

  Furthermore, a second determination means can be provided at the beginning of the first and second speaker lines. In this case, the second determination means determines the output voltage of the power amplifier. The first determining means determines that the impedance between the second speaker line and the common potential point is higher than a predetermined impedance, and the second determining means determines that there is an output voltage of the power amplifier. The first or second speaker line is determined to be disconnected, the first determining means determines that the impedance between the second speaker line and the common potential point is higher than a predetermined impedance, and When the second determination means determines that there is no output voltage of the power amplifier, it determines that the first and second speaker lines are short-circuited. This determination can be performed using, for example, a third determination unit to which the determination results of the first and second determination units are supplied, or the first determination unit is shared with the second speaker line. The second determination unit may be controlled by the first determination unit so that the second determination unit performs the determination only when it is determined that the impedance to the potential point is higher than a predetermined impedance. That is, when a short circuit or disconnection occurs in the first and second speaker lines, the second determination means detects the presence or absence of the output of the power amplifier. In the case, it is determined as a short circuit.

  When the first or second speaker line is disconnected, the output of the power amplifier is generated. However, when the short circuit is generated between the first and second speaker lines, the output voltage of the power amplifier is generated. do not do. Therefore, by combining the first determination unit and the second determination unit, it is possible to determine whether a disconnection has occurred or a short circuit has occurred.

When the power amplifier is provided with a monitor terminal for generating a monitor output voltage, fourth determination means for detecting the presence or absence of this monitor voltage is provided, and the determination results of the first, second and fourth determination means (1) The fourth determination means determines that there is a monitor output voltage, and the first determination means determines that the impedance between the second speaker line and the common potential point is higher than a predetermined impedance. And the second determination means determines that the output voltage of the power amplifier is present, the first or second speaker line is determined to be disconnected, and (2) the fourth determination means includes the monitor output voltage. The first determination means determines that the impedance between the second speaker line and the common potential point is higher than a predetermined impedance, and the second determination means When it is determined that there is no output voltage of the amplifier, it is determined that the first and second speaker lines are short-circuited. (3) The fourth determination means determines that there is no monitor output voltage, and the first determination means is the second. When it is determined that the impedance between the speaker line and the common potential point is higher than a predetermined impedance, and the second determination means determines that there is no output voltage of the power amplifier, it is determined that the power amplifier has failed. You can also. In this case, the third determination unit supplies the determination results of the first, second, and fourth determination units to the third determination unit, and the third determination unit performs the determinations (1) to (3) above. The determination means can also be configured.

  In one embodiment, the impedance connection means includes detection means for detecting the presence or absence of the AC signal at the ends of the first and second speaker lines, and when the detection means detects the AC signal, the impedance element Switching means for connecting between the terminal of the second speaker line and the common potential point. As the detecting means, for example, a rectifying / smoothing means for rectifying and smoothing an AC signal can be used. In this case, a control means for closing the switching means when the output of the rectifying and smoothing means is larger than a predetermined reference value is provided.

In the speaker line inspection apparatus according to another aspect of the present invention, the start ends are respectively connected to the two output terminals of the power amplifier, and apart from the start ends of the first and second speaker lines of the plurality of systems to which the speakers are connected. When an AC signal is detected at the end located, the impedance connection means provided in each system connects the impedance element between the end of the second speaker line of each system and the common potential point. One terminal of the AC signal source is connected to the common potential point, and the other terminal is connected to the start end of the second speaker line of each system via another impedance element. This AC signal source sequentially generates AC signals of different frequencies as many as the number of each system. The determination means measures the impedance between the start end of the second speaker line of each system and the common potential point for each of the alternating signals of the different frequencies, and in any system based on the measured impedance Determine if a break or short circuit has occurred.

  In this aspect, the impedance element is connected between the second speaker line of the system in which no disconnection or short circuit has occurred and the common potential point. When the AC signal source generates AC signals having different frequencies, the impedance values indicated by these impedance elements change. By measuring the impedance for each frequency, it is possible to determine in which system the disconnection or the short circuit has occurred.

The terminal device for a speaker line inspection device according to another aspect of the present invention has detection means for detecting the presence or absence of an AC signal at the ends of the first and second speaker lines. The first and second speaker lines have start ends connected to the two output terminals of the power amplifier, respectively, and a speaker connected between them. Furthermore, a determination means for measuring the impedance between the starting end of the second speaker line and the common potential point in a DC manner and determining whether the impedance is larger than a predetermined value is the second speaker line. Connected between the common potential points. When the detecting means detects the AC signal, the switching means connects an impedance element having a predetermined impedance between the terminal at a position away from the starting end of the second speaker line and the common potential point. .

  When this terminal device is provided at the terminals of the first and second speaker lines, the impedance is measured between the starting end of the second speaker line and the reference potential point, so that the first and second speaker lines are connected. Short circuit or disconnection of the first or second speaker line can be detected.

  As described above, according to the present invention, disconnection or short circuit of the speaker line can be detected, and it is not necessary to pass a DC signal to the two speaker lines for this detection. Therefore, a capacitor is connected in series with the speaker. It is not necessary to connect between the speaker lines after connecting the terminals, so that an increase in cost can be prevented, and a line for transmitting the DC signal flowing through the speaker lines to the determination device is provided at the terminal of the speaker line. It is not necessary to lay from the device to the determination device, so that the cost can be reduced and the laying work can be simplified.

  A speaker line inspection apparatus according to an embodiment of the present invention is used with a loudspeaker as shown in FIG. The loudspeaker has a power amplifier 2 to which an audio frequency signal such as a sound signal from a sound source such as a microphone 4 is supplied. This audio signal is amplified by the power amplification stage 3 of the power amplifier 2 and supplied to the primary winding 6p of the output transformer 6 provided on the output side thereof. The output transformer 6 has two secondary windings 6s1 and 6s2. The secondary winding 6s1 is for output, and the secondary winding 6s2 is for monitoring. Both ends of the secondary winding 6s1 are once drawn into the determination device 8 of the inspection apparatus and connected to the first ends of the first and second speaker lines, for example, the hot line 10 and the cold line 12. For example, in a building such as a building, the hot line 10 and the cold line 12 are laid so as to pass through various places in the building from the place where the power amplifier 2 is installed. .. Are connected between the hot line 10 and the cold line 12 at each location.

  The determination device 8 includes a first inspection signal source 16 as an AC signal source that generates an AC signal used for inspection of the hot line 10 and the cold line 12. The first inspection signal source 16 generates a signal having an inaudible frequency, for example, 40 Hz, as the first inspection signal. The first inspection signal source continuously generates the first inspection signal. This first inspection signal is mixed with an audio signal by mixing means, for example, a mixer 18, supplied to the power amplifier 2, amplified there, and flows through the hot line 10, the speakers 14, and the cold line 12.

  A terminal device 20 that constitutes an inspection device together with the determination device 8 is provided at the terminals of the hot line 10 and the cold line 12. The terminal device 20 includes an impedance element, for example, a resistor 22 having a predetermined impedance value, specifically, a resistance value of 470 kΩ, and a switching element connected in series with the resistor 22, for example, a normally open switching element 24. It has a circuit. One end of the series circuit is connected to one of the hot line 10 and the cold line 12, for example, a terminal of the cold line 12. The other end of this series circuit is connected to a common potential point, for example, a ground potential point. A detection unit 26 is connected to the terminals of the hot line 10 and the cold line 12, and when the first inspection signal is detected by the detection unit 26, the detection unit 26 closes the switching element 24 and grounds the cold line 12 and the ground. A resistor 22 is connected to the potential point.

  As shown in FIG. 2, for example, the detection unit 26 includes a rectifier circuit 28 whose input side is connected to terminals of the hot line 10 and the cold line 12, and the output of the rectifier circuit 28 is smoothed by a smoothing capacitor 30. The positive side of the smoothing capacitor 30 is connected to the collector of the transistor 32 functioning as a comparator, and the emitter thereof is connected to one end of the resistor 34. The other end of the resistor 34 is connected to the anode of the photodiode 24 a of the photo MOS relay that functions as the switching element 24, and the cathode is connected to the negative electrode of the smoothing capacitor 30. The base of the transistor 32 is connected to the cathode of a Zener diode 36 that functions as a reference power supply, and the anode is connected to the negative electrode of the smoothing capacitor 30. A capacitor 38 is connected in parallel with the Zener diode 36, and a resistor 40 is connected between the collector and base of the transistor 32.

  In this configuration, the first inspection signal is continuously supplied between the hot line 10 and the cold line 12, and a predetermined voltage is generated across the smoothing capacitor 30, which is based on the reference voltage set by the Zener diode 36. Becomes larger, the transistor 32 becomes conductive, the photodiode 24a emits light, and accordingly the photoelectric MOS transistor 24b of the photoMOS relay 24 becomes conductive, and the resistor 22 is connected between the terminal of the cold line 12 and the ground potential point. .

On the other hand, when the hot line 10 or the cold line 12 is disconnected, the first inspection signal is not supplied to the input side of the rectifier circuit 28, and a predetermined voltage is not generated between both ends of the smoothing capacitor 30. The same applies when the hot line 10 and the cold line 12 are short-circuited. Accordingly, the resistor 22 is not connected between the end of the cold line 12 and the ground potential point.

  Therefore, the determination device 8 measures the impedance between the starting end of the cold line 12 and the ground potential point, and if the value is close to the value of the resistor 22, the hot line 10 and the cold line 12 are disconnected. It can be seen that no short circuit occurs between the hot line 10 and the cold line 12. On the other hand, if the impedance between the starting end of the cold line 12 and the ground potential point is a value that is considerably larger than the resistance value of the resistor 22, whether the hot line 10 or the cold line 12 is broken or the hot line 10 It can be seen that a short circuit has occurred between the cold lines 12.

  Therefore, the starting end of the cold line 12 is connected via a resistor 44 to the positive electrode of the DC power supply 42 whose negative electrode is connected to the ground potential point. Further, the starting end of the cold line 12 is connected to a comparison means, for example, a comparator 46 via a DC detection filter 47. The comparator 46 is supplied with a reference voltage from a reference power supply 48. The reference voltage is set to a voltage somewhat higher than the voltage generated between the cold line 12 and the reference potential point when the resistor 22 is connected between the cold line 12 and the reference potential point. Yes. The comparator 46 is configured to output a normal signal when the voltage between the cold line 12 and the reference potential point is lower than the reference voltage, and an abnormal signal when the voltage is higher than the reference voltage. In this way, the DC power source 42, the comparator 46, and the reference power source 48 constitute a first determination means. Depending on whether the comparator 46 outputs a normal signal or an abnormal signal, the hot line 10, the cold line It can be determined whether or not 12 short circuits or disconnections have occurred.

  If the first inspection signal itself is detected to determine whether the first inspection signal has been transmitted to the end of the hot line 10 and the cold line 12, whether the hot line 10 and the cold line 12 are disconnected is determined from the end. If the determination device 8 located at a distant position is to be detected, a return line for transmitting the first inspection signal from the end of the hot line 10 and the cold line 12 to the determination device must be laid. However, such a return line is not required for this inspection apparatus. Moreover, when direct current is passed through the hot line 10 and the cold line 12 as in the above-described prior art and the current is to be detected by the determination device 8, a resistor is connected to the end of the hot lines 10 and 12, Each speaker 14 must be connected with a capacitor in series. However, this inspection apparatus does not require such a capacitor at all. In addition, since the first inspection signal used for this inspection has an inaudible frequency, even if the first inspection signal is always supplied to the hot line 10 and the cold line 12, the broadcasting by the microphone 4 is an obstacle. Not give. Therefore, it is always possible to inspect whether a short circuit or a disconnection has occurred.

  By the way, when the cold line 12 is connected to the ground potential point for some reason, that is, it may be grounded. In order to detect whether or not this ground fault has occurred, the following configuration is also employed. The starting end of the cold line 12 is connected to a comparison means, for example, a comparator 54 via a direct current detection filter 47. The comparator 54 is supplied with a reference voltage from a reference power source 56. The reference voltage is lower than the voltage generated between the cold line 12 and the reference potential point when the resistor 22 is connected between the cold line 12 and the reference potential point, and a ground fault occurs. Is set to the highest voltage that is expected to occur. The comparator 54 is configured to output a ground fault signal when the voltage between the cold line 12 and the reference potential point is lower than the reference voltage, and to output a normal signal when the voltage is higher than the reference voltage.

  By the way, in the determination by the first determination means, it is determined that either a disconnection or a short circuit has occurred, but it is not determined which one has occurred. Therefore, the determination result by the second determination unit and the determination result by the first determination unit are combined.

  The determination device 8 has a second inspection signal source 58 for use in the second determination means. The second inspection signal source 58 generates a signal having a non-audible frequency, for example, 20 KHz, as the second inspection signal. The frequency of the second inspection signal is different from the frequency of the first inspection signal. The second inspection signal is supplied to the mixer 18. In order to detect the second inspection signal, the start ends of the hot line 10 and the cold line 12 are drawn into the determination device 8 and supplied to the second determination means, for example, the detection circuit 62. Various detection circuits 62 can be used. For example, the voltage between the hot line 10 and the cold line 12 is measured, the voltage is compared with a predetermined reference voltage, and the measured voltage is larger than the reference voltage. It is possible to use one that outputs a disconnection or normal detection signal and outputs a short circuit detection signal when the measured voltage is smaller than the reference voltage.

  The first determination means can only detect whether it is normal, as described above, or a disconnection or a short circuit has occurred. On the other hand, the second determination means can determine only whether the connection is broken, normal, or short-circuited. Therefore, when both are combined, the comparator 46 of the first determination means generates an abnormal signal, and the detection circuit 62 as the second determination means generates a normal or disconnection detection signal. It is determined that the line 12 is disconnected. Further, when the comparator 46 of the first determination means generates an abnormal signal and the detection circuit 62 as the second determination means generates a short-circuit detection signal, the hot line 10 and the cold line 12 are short-circuited. Is determined.

  Incidentally, in addition to the short circuit between the hot line 10 and the cold line 12, the comparator 46 of the first determination means generates an abnormal signal and the detection circuit 62 as the second determination means generates a short circuit detection signal. There is. This is a case where the power amplifier 2 has failed and is not generating an output. Therefore, the output of the monitoring secondary winding 6 s 2 of the output transformer 6 of the power amplifier 2 is drawn into the determination device 8 and supplied to the detection circuit 64. The detection circuit 64 is configured in the same manner as the detection circuit 62. When the measured impedance is smaller than the reference impedance, it is determined that the power amplifier 2 is not generating an output, and a fault signal is generated. When the measured impedance is larger than the reference impedance, it is determined that the power amplifier 2 is operating normally, and a normal signal is generated. Even when the hot line 10 and the cold line 12 are short-circuited and no output is generated between the secondary windings 6s1, as long as the power amplifier 2 is normal, an output is generated between the monitoring secondary windings 6s2. ing. Accordingly, the detection circuit 64 can determine whether the power amplifier 2 is normal or faulty.

When the detection circuit 64 generates a normal signal, the comparator 46 of the first determination unit generates an abnormal signal, and the detection circuit 62 as the second determination unit generates a short-circuit detection signal, the hot line 10 and It is determined that the cold line 12 is short-circuited. When the detection circuit 64 generates an abnormal signal, the comparator 46 of the first determination means generates an abnormal signal, and the detection circuit 62 as the second determination means generates a short-circuit detection signal, the power amplifier 2 fails. Is determined.

  In order to make such a determination, an abnormality or normal signal of the comparator 46, a normal or disconnection detection signal detection or short circuit detection signal of the detection circuit 62, and a normal or failure signal of the detection circuit 64 are detected by a third determination means, for example, It is supplied to the logic circuit 66 and performs the logic determination as described above.

  As shown in FIG. 3, switching elements 66a and 66b are provided on the input side of the detection circuit 62. When these switching elements 66a and 66b are closed, the hot line 10 and the cold line are provided on the input side of the detection circuit 62. 12 and the switch elements 66a and 66b are configured to close when the comparator 64 of the first determination means generates an abnormal signal, the hot line 10 and the cold line 12 are normal. Sometimes, the detection circuit 62 is not connected to the hot line 10 and the cold line 12. Therefore, the detection circuit 62 generates a disconnection or normal detection signal only when the hot line 10 and the cold line 12 are disconnected, and the detection circuit 62 generates a disconnection or a short circuit in the hot line 10 and the cold line 12. Can be detected. In this case, the detection circuit 64 is used alone, and when the detection circuit 64 generates a failure signal, it is determined that the power amplifier 2 is in failure.

  As shown in FIG. 4, the amplifier 2, the hot line 10a, the cold line 12a, the speakers 14a, 14a... Constitute a loudspeaker, and no short circuit or disconnection occurs in the hot line 10a and the cold line 12a. In order to check whether the hot line 10a, the end of the cold line 12a are connected to the detection circuit 62 by the return lines 66a, 66b, the hot line 10b, the cold line 12b, the speakers 14b, 14b,. There are things to do. In this case, if it is attempted to inspect the short circuit or disconnection of the hot line 10b and the cold line 12b added by the detection circuit 62, the return lines 66a and 66b are connected to the hot line 10b and the cold line as indicated by a one-dot chain line. The return lines 66a and 66b need to be laid again so as to be connected to the end of the line 12b. However, it is very troublesome to re-lay the return lines 66a and 66b in a building or the like.

  Therefore, in order to eliminate the need for re-laying the return lines 66a and 66b, the terminal device 20 is provided at the terminals of the hot line 10b and the cold line 12b, and the first determination means is configured in the determination device 8a. By providing the direct current power source 42, the resistor 44, the comparator 46, the reference power source 48, and the like, it is possible to detect a short circuit or disconnection of the hot line 10b and the cold line 12b.

  Further, as shown in FIG. 5, the output of the amplifier 2 may be distributed and supplied to a plurality of systems, for example, two systems. In this case, one system is configured by a hot line 10c, a cold line 12c, speakers 14c, 14c,..., And the other system is configured by a hot line 10d, a cold line 12d, speakers 14d, 14d,. ing. When distributing to a plurality of systems as described above, when the terminal devices 20c and 20d having the same configuration as the terminal device 20 described above are provided in the terminals of each system and the determination device 8 described above is used, It can be seen that a short circuit or disconnection has occurred in either of them, but it cannot be determined in which system a short circuit or disconnection has occurred.

  Therefore, in the aspect of FIG. 5, the determination device 8 c uses the AC signal source 42 c as the inspection signal source instead of the DC power source 42. The AC signal source 42c generates an inaudible frequency having a different frequency, for example, an AC signal having a frequency selected from either f1 or f2. Further, the terminal device 20c is configured such that the impedance element 22c shows a predetermined impedance, for example, a resonance impedance Z1, for example, at the frequency f1, and shows a predetermined impedance Z2 (Z1 <Z2), at the frequency f2. Similarly, the terminal device 20d is configured such that the impedance element 22d indicates a predetermined impedance Z2 at, for example, the frequency f1, and indicates a predetermined impedance at the frequency f2, for example, the resonance impedance Z1 (Z1 <Z2). The impedance elements 22c and 22d can be constituted by, for example, a resistor and capacitor series circuit, a resistor and coil series circuit, a resistor, capacitor and coil series circuit, or a capacitor and coil series circuit.

  A connection point between the start ends of the cold lines 12c and 12d and the resistor 44 is connected to an inspection signal extraction unit, for example, a bandpass filter 47c. The band pass filter 47c is configured to be able to switch the pass band between a state in which the pass band includes the frequency f1 and a state in which the frequency f2 is included. The output level of the band pass filter 47 c is detected by the level detection circuit 70 and supplied to the comparator 48. The reference voltage is supplied from the reference voltage source 48 to the comparator 48.

This reference voltage is obtained when an alternating current signal having a frequency f1 is supplied and an alternating current signal having a frequency f2 is supplied in a state where both of the impedance elements 22c and 22d are connected to the reference potential point. When the impedance when these terminals are viewed from the start ends of the second speaker lines 12c and 12d is a parallel impedance value of Z1 and Z2, the output voltage of the level detection circuit 70 is set to be lower than the reference voltage. .

Further, this reference voltage is obtained when an AC signal having a frequency f1 is supplied in a state where the impedance element 22c is connected to the reference potential point and the impedance element 22d is not connected to the reference potential point, that is, When the impedance when the terminal side is viewed from the beginning of the speaker lines 12c and 12d is the impedance Z1 of the impedance element 22c, the output of the level detection circuit 70 is smaller than the reference voltage and the AC signal having the frequency f2 is supplied. In other words, when the impedance viewed from the terminal ends of the second speaker lines 12c and 12d is the impedance Z2 of the impedance element 22c, the output of the level detection circuit 70 is set to be larger than the reference voltage. ing.

Further, the reference voltage is supplied when an AC signal having a frequency f1 is supplied in a state where the impedance element 22c is not connected to the reference potential point and the impedance element 22d is connected to the reference potential point, that is, When the impedance viewed from the terminal ends of the speaker lines 12c and 12d is the impedance Z2 of the impedance element 22d, the output of the level detection circuit 70 is larger than the reference voltage and an AC signal having a frequency f2 is supplied. In other words, when the impedance viewed from the beginning of the second speaker lines 12c and 12d is the impedance Z1 of the impedance element 22d, the output of the level detection circuit 70 is set to be smaller than the reference voltage. ing.

In addition, when both the impedance elements 22c and 22d are not connected to the ground potential point and an AC signal of any of the frequencies f1 and f2 is supplied, that is, from the beginning of the second speaker lines 12c and 12d. The reference voltage is set so that the output voltage of the level detection circuit 70 becomes larger than the reference voltage when the impedance of the terminal side is infinite.

The comparator 48 outputs a large signal when the output of the level detection circuit 70 is larger than the reference voltage, and outputs a small signal when the output is small. This output is supplied to the control unit 72. The control unit 72 also controls the AC signal source 42c and the bandpass filter 47c so that when the AC signal source 52c generates an AC signal having the frequency f1, the bandpass filter 47c passes the AC signal having the frequency f1. In addition, when the AC signal source 52c generates an AC signal having the frequency f2, the bandpass filter 47c passes the AC signal having the frequency f2.

  In this configuration, when the hot lines 10c and 10d and the cold lines 12c and 12d are both normal, the impedance elements 22c and 22d are connected to the ground potential point. At this time, even when either of the signals of the frequencies f1 and f2 is supplied, the impedance when these terminal sides are viewed from the start ends of the second speaker lines 12c and 12d is a parallel impedance of Z1 and Z2. Therefore, in any case, the comparator 48 supplies a small signal to the control unit 72, and the control unit 72 determines that both systems are normal.

  When the hot line 10c and the cold line 12c are normal and the hot line 10d and the cold line 12d are disconnected or short-circuited, when the AC signal f1 is supplied, these terminals are connected from the beginning of the second speaker lines 12c and 12d. The impedance viewed from the side is the impedance Z1 of the impedance element 22c. When the comparator 48 generates a small signal and the AC signal f2 is supplied, the terminal side of these terminals from the start ends of the second speaker lines 12c and 12d. Is the impedance Z2 of the impedance element 22c, and the comparator 48 generates a large signal. Therefore, the control unit 72 determines that a disconnection or a short circuit has occurred in the hot line 10d and the cold line 12d.

  When the hot line 10c and the cold line 12c are disconnected or short-circuited, and the hot line 10d and the cold line 12d are normal, when the AC signal f1 is supplied, the terminals of the terminals from the beginning of the second speaker lines 12c and 12d are connected. The impedance seen is the impedance Z2 of the impedance element 22d, and the comparator 48 generates a large signal. When the AC signal f2 is supplied, the terminal side is viewed from the beginning of the second speaker lines 12c and 12d. The impedance is the impedance Z1 of the impedance element 22d, and the comparator 48 generates a small signal. Therefore, the control unit 72 determines that a disconnection or a short circuit has occurred in the hot line 10c and the cold line 12c.

  When an AC signal f1 is supplied when a disconnection or a short circuit occurs in both systems of the hot lines 10c and 10d and the cold lines 10d and 12d, these terminals are connected from the beginning of the second speaker lines 12c and 12d. The impedance seen is infinite and the comparator 48 generates a large signal. In this state, when the AC signal f2 is supplied, the impedance of the second speaker lines 12c and 12d when viewed from the terminal ends from the start ends is infinite, and the comparator 48 generates a large signal. Therefore, the control unit 72 determines that both systems are disconnected or short-circuited.

  In this way, the control unit 72, the comparator 46, the band pass filter 47c, and the level detection circuit 70 constitute a determination unit. In this example, an example of two speaker lines is shown, but more speaker lines can be connected. However, in that case, the AC signal source 42c generates AC signals of different frequencies corresponding to the number of systems, and the impedance of impedance elements of different systems for each frequency indicates a predetermined impedance, for example, a resonance impedance. The output of the level detection circuit 70 is compared with an appropriate reference voltage at different frequencies.

  In each of the above-described embodiments, the first determination means includes the DC power supply 42, the resistor 44, the comparator 46, the DC detection filter 47, the reference power supply 48, etc., and the determination means includes the control unit 72 and the comparison unit. The detector 46, the band-pass filter 47c, the level detection circuit 70, etc. are measured, and the voltage between the cold line and the reference potential point is measured and the voltage and the reference voltage are compared in the same manner as the detection circuits 62 and 64. A configuration that measures the voltage between the cold line and the reference potential point and the current flowing through the cold line, obtains the impedance from the measured value, and compares this impedance with the reference impedance Can also be adopted. The detection circuit 62 can also be configured to compare a filter that detects the inspection signal, a circuit that rectifies and smoothes the output of the filter, and the rectified and smoothed output with a reference signal. A similar configuration can be adopted for the detection circuit 64. In the above-described embodiment, the first and second inspection signals are used. However, only one of the inspection signals can be used. In each of the above embodiments, the ground potential point is used as the common potential point. However, for example, a line for a common potential point, for example, a shield line, is laid from the terminal device 20 to the determination device 8, and the common potential point of the determination device 8 is used. You may connect with. In the above-described embodiment, the first inspection signal is used. However, the use of the first inspection signal may be stopped, and for example, the audio signal from the microphone 4 may be detected by the detection circuit 26.

It is a block diagram of a loudspeaker using the inspection device of one embodiment of the present invention. It is a circuit diagram of the terminal device used in the inspection apparatus of FIG. It is a block diagram which shows a part of modification of the inspection apparatus of FIG. It is a block diagram of a loudspeaker using the inspection device of other embodiments of the present invention. It is a block diagram of another modification of the inspection apparatus of FIG.

Explanation of symbols

2 Power amplifier 10 Hot line (first speaker line)
12 Cold line (second speaker line)
14 Speaker 22 Resistor (impedance element)
24 switching element 26 detection circuit 44 resistor (first determination means)
46 comparator (first determination means)
48 Reference power supply (first determination means)

Claims (6)

First and second in a loudspeaker in which a starting end is connected to each of the two output terminals of the power amplifier and a speaker is connected between the first and second speaker lines whose ends are located away from the starting end. An impedance connecting means for connecting an impedance element between the end of the second speaker line and the common potential point when an AC signal supplied from the start end side is detected at the end of the speaker line;
First determination means for determining whether or not an impedance between a starting end of a second speaker line and the common potential point is a predetermined impedance;
A speaker line inspection device provided.   2. The speaker line inspection apparatus according to claim 1, wherein the first determination means has one terminal connected to the common potential point and the other terminal connected to the starting end of the second speaker line via another impedance element. A speaker line comprising: a direct current power source; and a comparing means for comparing a voltage between a starting end of the second speaker line and the common potential point with a reference voltage predetermined with respect to the common potential point. Inspection device.   2. The speaker line inspection apparatus according to claim 1, further comprising: a second determination unit that is connected to the first ends of the first and second speaker lines and determines whether or not there is an output of the power amplifier. When the first determination means determines that the impedance between the common potential point is higher than a predetermined impedance, and the second determination means determines that the output of the power amplifier is present, the first or second The first determination means determines that the speaker line is disconnected, the impedance between the second speaker line and the common potential point is higher than a predetermined impedance, and the second determination means determines the power. A speaker line inspection device that determines that the first and second speaker lines are short-circuited when it is determined that there is no output from the amplifier. 2. The speaker line inspection apparatus according to claim 1, wherein the impedance connection means detects the presence or absence of the AC signal at the ends of the first and second speaker lines, and the detection means detects the AC signal. A speaker line inspection apparatus comprising switching means for connecting the impedance element between a terminal of a second speaker line and the common potential point. The plurality of systems in a loudspeaker in which a starting end is connected to each of the two output terminals of the power amplifier, and a speaker is connected between each of the first and second speaker lines of the plurality of systems whose ends are located away from the starting end. Impedance connection means for connecting an impedance element between the end of the second speaker line of each system and the common potential point when an AC signal is detected at the ends of the first and second speaker lines of
One terminal is connected to the common potential point, the other terminal is connected to the start end of the second speaker line of each system via another impedance element, and the alternating current has the same number of different frequencies as the number of each system. An AC signal source for generating signals in sequence;
The impedance between the start end of the second speaker line of each system and the common potential point is measured for each AC signal of the different frequency, and a disconnection or a short circuit occurs in any system based on the measured impedance. A determination means for determining whether or not it occurs,
A speaker line inspection device provided. First and second speaker lines having start ends connected to two output terminals of the power amplifier, respectively, between which a speaker is connected and between the start end of the second speaker line and the common potential point A determination means for measuring the impedance and determining whether the impedance is greater than a predetermined value is applied to the first and second speaker lines connected between the second speaker line and the common potential point. Detecting means for detecting the presence or absence of an AC signal supplied from the starting end side at a terminal distant from the starting end, and when the detecting means detects the AC signal, the impedance element is connected to the second speaker line. Switching means connected between the terminal and the common potential point;
A terminal device for a speaker line inspection apparatus.

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