Light monitoring and control system, master station, slave station, and communication method

Abstract

To provide a lighting monitoring and control system with improved responsiveness at low cost.SOLUTION: A lighting monitoring and control system includes a master station and a slave station. The master station communicates with the slave station via a power line for supplying power to airport lights. The slave station is connected to the power line via a transformer. The transformer is connected to a power line on the primary side thereof, and supplies power extracted from the secondary side to the lights connected to the slave station. The master station includes a modulation unit and an injection unit. The modulation unit modulates a carrier signal with a code of a plurality of bits according to a modulation scheme representing a symbol by a combination of a frequency shift and a phase shift to generate a modulated signal. The injection unit injects the modulated signal into the power line in synchronization with the power supply cycle of the power. The slave station includes a receiver and a demodulator. The receiver receives a modulated signal from the power waveform on a secondary side of the transformer. The demodulator demodulates the received modulated signal to reproduce the code.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a light monitoring and control system, a master station, a slave station, and a communication method. [Background technology]

[0002] Light monitoring and control systems are essential for the safe operation of aircraft taking off and landing at airports. At airports, a wide variety of lights, such as guide lights and control lights, are installed in large numbers on runways and taxiways. In many systems, the power lines that supply power to the lights also serve as the communication medium for monitoring and controlling the lights. This type of method is called power line carrier. Power line carriers are widely used in stop line light systems (STBLs) that turn lights on and off to guide aircraft on the ground, runway status light systems (RWSLs), and for detecting broken light cores.

[0003] In existing airport facility monitoring and control systems using power line carriers, commands related to lighting monitoring and control were generated by changing the signal injection pattern into the power line. Power lines are in extremely harsh environments for communication, as they can be laid over distances of several to tens of kilometers and are unshielded. For this reason, commands were previously created by arranging one bit indicating whether a signal is present or absent, which was not necessarily excellent in terms of responsiveness or versatility.

[0004] For example, there is a known technology that can realize communication using high frequencies of 10k to 150kHz by constructing a dedicated power circuit and using the Orthogonal Frequency Division Multiplexing (OFDM) method. This technology can increase the communication rate, but it comes at a high cost. In Japan, due to restrictions in the Radio Law, it is difficult to use such high frequencies, especially around aircraft. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4008693 [Patent Document 2] US Patent Application Publication No. 2005 / 0253929 Summary of the Invention [Problem to be solved by the invention]

[0006] In light monitoring and control systems using power line carriers, it has been difficult to speed up control response due to the harsh communication environment. There is a demand for technology that can withstand adverse conditions, improve response, and realize light control without increasing costs. Therefore, an object is to provide a light monitoring and control system, a master station, a slave station, and a communication method with improved responsiveness at low cost. [Means for solving the problem]

[0007] According to an embodiment, the light monitoring and control system includes a master station and a slave station. The master station communicates with the slave station via a power line that supplies power to the airport lights. The slave station is connected to the power line via a transformer. The transformer has a primary side connected to the power line and supplies power extracted from a secondary side to the lights connected to the slave station. The master station includes a modulation unit and an injection unit. The modulation unit generates a modulated signal by modulating a carrier signal with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift. The injection unit injects the modulated signal into the power line in synchronization with the power supply cycle of the power. The slave station includes a receiving unit and a demodulation unit. The receiving unit receives the modulated signal from the power waveform on the secondary side of the transformer. The demodulation unit demodulates the received modulated signal to reproduce the code. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a light monitoring and control system according to an embodiment. [Diagram 2] FIG. 2 is a functional block diagram showing an example of the master station 3. As shown in FIG. [Diagram 3] FIG. 3 is a functional block diagram showing an example of the slave station 6. As shown in FIG. [Figure 4] FIG. 4 is a diagram for explaining a modulation method in the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a signal bandwidth. [Figure 6] FIG. 6 is a functional block diagram showing the demodulation process in the slave station 6. As shown in FIG. [Figure 7] FIG. 7 is a diagram showing a change in phase. [Figure 8] FIG. 8 is a diagram for explaining the phase determination. [Figure 9] FIG. 9 is a diagram for explaining synchronization with a reference signal. [Figure 10] FIG. 10 is a diagram illustrating an example of a communication sequence. [Figure 11] FIG. 11 is a diagram for explaining an increase in the child station signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a light monitoring and control system according to an embodiment. In FIG. 1, a power source (CCR) 1 installed in a power station building at an airport is connected to a power line (light circuit cable) 8 via a bypass filter 4. The power line 8 connects the primary sides of multiple rubber transformers 5 in series. A slave station 6 is connected to each secondary side of the rubber transformer 5. Furthermore, a light 7 is connected to each slave station 6. The rubber transformer 5 ensures isolation between the power line 8 and the slave station 6, but power from the power line 8 is supplied to the slave station 6 and the light 7, so that a constant current flows to each light.

[0010] The bypass filter 4 is installed, for example, near the power source 1, and separates noise in the communication route of the power line 8 from power source noise. For example, the current flowing through the LRC resonant circuit is acquired and refined by a filter to obtain a commercial power waveform. As shown in FIG. 1, by inserting the bypass filter 4 between the power source (CCR) 1 side and the power line 8, the signal frequency bands used by the power source 1 and the lamp 7 are separated. That is, an LRC resonant circuit is constructed by L (coil), R (resistance), and C (capacitor), so that the signal used on the lamp circuit side circulates on the lamp circuit side, and the CCR noise circulates on the power source side.

[0011] Furthermore, a master station 3 is connected to a bypass filter 4. The master station 3 functions by receiving power from a power source 1, and communicates with a subordinate slave station 6 via a power line 8 by power line carrier. The power source 1 may be multiplexed into a normal power source 1-1 and a standby power source 1-2. In addition, a stabilization device (OP / C) 2 may be provided between the power source 1 and the bypass filter 4.

[0012] The master station 3 is accommodated in a master unit 10 via a control LAN (Local Area Network) 9. The master unit 10 is a robust computer such as a PLC (Programmable Logic Controller). The master unit 10 is further connected to a monitoring console 11 via the control LAN 9. The monitoring console is, for example, a general-purpose server computer, and is equipped with a monitor that displays the runway status in real time.

[0013] In Fig. 1, the master station 3 transmits, for example, a query command periodically to the slave stations 6 connected to a common power line 8. The slave stations 6 transmit a response signal to the master station 3 at a timing according to the address assigned to them. The slave stations 6 monitor the status of the lights 7, and if a malfunction such as a burned-out bulb occurs, they notify the master station 3. This allows the location of the broken core to be detected immediately and displayed on the monitor of the monitoring console 11. The operator can refer to this display and take appropriate measures.

[0014] Similarly, in a stop line light system or a RWSL system that controls lights, control of lights 7 is performed by power line carrier communication using power lines 8. Based on information acquired by an aircraft detection sensor or a ground radar, a control command is given from a master station 3 to a slave station 6, and the slave station 6 controls the ON / OFF of the lights under its control. This makes it possible to realize ground guidance of aircraft by controlling the lights.

[0015] Fig. 2 is a functional block diagram showing an example of the master station 3. In Fig. 2, the power line on the IN side in relation to the power source 1 is referred to as the F side, and the power line on the OUT side is referred to as the R side. A signal from the slave station 6 is received at two points, the F side and the R side. That is, even if the reception level of one signal is low, a diversity configuration is adopted in which the other can compensate. In the embodiment, a signal is injected into the power line 8 on the F side.

[0016] The master station 3 includes a signal processing unit 31, a processor 32, interface units 33 and 38, a waveform shaping unit 34, an amplifier unit 35, a signal injection unit 36, and a power supply waveform acquisition unit 37. Among these, the power supply waveform acquisition unit 37 digitally converts the power supply waveform acquired from the bypass filter 4 and passes it to the processor 32.

[0017] The signal processing unit 31 includes a modem unit 31F and a modem unit 31R. The modem unit 31F generates a modulated signal by modulating the carrier signal on the F side with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift. The generated modulated signal is input to a signal injection unit 36 ​​via a waveform shaping unit 34 and an amplifier unit 35. The signal injection unit 36 ​​injects the modulated signal into the power line 8 in synchronization with the power supply cycle of the power source 1. The modem unit 31R generates a modulated signal by modulating the R-side carrier signal with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift. In the embodiment, a modulation method is adopted in which a two-bit code is associated with four symbols represented by two different frequencies and phases, which may be called a dual modulation method.

[0018] The processor 32 provides a multi-bit code including a command to be transmitted to the slave station 6, the address of the master station 3, etc., to the signal processing unit 31 to generate a modulated signal. The processor 32 repeatedly executes a transmission / reception sequence including transmission of a code from the master station 3 to the slave station 6 and transmission of a response code from the slave station 6 to the master station 3.

[0019] Moreover, the modem unit 31F demodulates the signal waveform extracted on the F side and reproduces the response code from the slave station 6. The modem unit 31R demodulates the signal waveform extracted on the R side and reproduces the response code from the slave station 6. The reproduced code is passed to the processor 32 and processed. Various data included in the response code are then transmitted from the interface 38 to the parent unit 10 via the control LAN 9.

[0020] FIG. 3 is a functional block diagram showing an example of the slave station 6. The slave station 6 includes a processing unit 6A and a power line unit 6B. As shown in FIG. 3, the slave station 6 is installed between the rubber transformer 5 and the light 7. The power line unit 6B is connected to the secondary side of the rubber transformer 5, supplies power to the light 7, and inputs a power waveform to the receiving unit 60 of the processing unit 6A. The state of the light 7 is acquired by a signal acquiring unit 67 and passed to a core break control unit 64 of the processing unit 6A. The driving power of the slave station 6 is acquired from the power line 8 by a power acquiring unit 68. An aircraft detection sensor 12 for detecting an aircraft is connected to the secondary side of the rubber transformer 5. The lighting side is short-circuited.

[0021] The receiving section 60 of the processing unit 6A receives the modulated signal transmitted from the master station 3 from the power waveform on the secondary side of the rubber transformer 5. The received modulated signal is input to a PLD (Programmable Logic Device) 61. The PLD 11 demodulates the modulated signal and reproduces the code transmitted from the master station 3. The reproduced code is passed to a processor 62.

[0022] The processor 62 processes the code from the PLD 11, the data from the disconnection control unit 64, and the data from the aircraft detection sensor 12 via the sensor interface 63, and generates a response code to the master station 3. The response code is input to the PLD 61. The PLD 61 generates a response signal by modulating a carrier signal with the response code using the modulation method (dual modulation method) of the embodiment. The response signal is passed to the transmission control unit 65.

[0023] The transmission control unit 65 controls the transmission circuit 66 of the power line unit 6B to inject a response signal into the power line 8. As a result, the response signal is transmitted to the master station 3 via the power line 8. In particular, in the embodiment, the transmission circuit 66 shorts / opens the secondary side of the transformer in synchronization with the power supply cycle to generate an overvoltage, and transmits the response signal using this overvoltage.

[0024] The transmission circuit 66 opens and closes the power supply circuit like a switch, thereby generating an overvoltage on the secondary side of the rubber transformer 5. By using this overvoltage as a signal, it becomes possible to generate a signal with low power consumption of 10W or less.

[0025] FIG. 4 is a diagram for explaining a modulation method in an embodiment. As shown in FIG. 4(a), the well-known methods are quadrature phase shift keying (QPSK), which allocates a signal to a phase of every 90 degrees and codes it, and quadrature frequency shift keying (QFSK), which allocates four frequencies to each code. However, QPSK modulation requires a relatively wide band to determine the phase of 90 degrees. QFSK modulation requires the use of four frequencies, and if the frequencies are too far apart, some codes may or may not reach one signal due to the effects of standing waves. Either method is difficult to apply to power line carriers in airports with harsh communication environments.

[0026] Therefore, in this embodiment, four codes are expressed by one signal by combining two frequencies (frequency shifts) and two phases (phase shifts) as shown in Fig. 4(b). That is, in this embodiment, different frequencies ch1 and ch2 are used (DFSK modulation) and two phases of 0° and 180° are used (DPSK modulation) to express four codes ("00" / "01" / "10" / "11") with one signal (symbol).

[0027] Fig. 5 is a diagram showing an example of a signal bandwidth. As shown in Fig. 5, for example, when a signal of 5 kHz is used and the signal width T is 1.4 ms, the band including the main lobe and one side lobe is 3.6 kHz (-2 / T) to 6.4 kHz (2 / T).

[0028] For example, if the power supply frequency is 50 Hz, a typical noise distribution on the power line 8 tends to be large at 20 times 50 Hz, 5000, 6000, and 7000, and is particularly noticeable at 4000 kHz. Phase modulation with a wide bandwidth is easily affected by noise, and even if the S / N ratio meets the specifications, there are cases where the phase cannot be read.

[0029] The total length of the power lines under one master station 3 can be several kilometers to tens of kilometers. For this reason, the power from the power source is not received at the same level at all lights, and peaks and valleys in the level occur. This is the effect of standing waves. For example, even in a place (light) where the level is high at 5 kHz, the level may become low at 6 kHz. This phenomenon can occur even with frequencies 1 kHz apart, so in the case of QFSK modulation, four frequencies must be used. For this reason, if the frequencies are separated too far, codes will occur that may or may not reach a single signal.

[0030] For example, even if a signal is transmitted at 100Hz intervals, only a difference of the order of error may be obtained. If the signal width T is 1.4ms, this is an interval of 1 / T=700Hz or less, which is a narrower band than the main lobe 4.3kHz (-1 / T) to 5.7kHz (1 / T), so there is no apparent difference. When transmitting 5.0 / 5.1. / 5.2. / 5.3kHz, the transmission frequency is maximum, but it may be seen as another frequency and only a slight difference may appear. For this reason, if spike noise of a specific frequency is introduced, it may not be possible to correctly capture the frequency. Ensuring a certain degree of power difference for each frequency can reduce the effects of external noise and ensure stable communication.

[0031] For example, when two frequencies are used with a frequency interval of 300 Hz, a difference of about 5.0 kHz power: 5.3 kHz power = 10:7 occurs at full scale. A clear difference occurs, making it possible to perform more stable communication. Therefore, in the embodiment, communication is performed between the master station 3 and the slave station 6 by power line carrier using two frequencies (DPSK modulation) and a modulation method using two phases of 0° / 180° (DFSK modulation).

[0032] Furthermore, in the embodiment, a plurality of carrier signals having different bands are modulated by a dual modulation method to generate a plurality of modulated signals having different bands. That is, the modem unit 31F (FIG. 2) modulates carrier signals having different frequencies F1 and F2 to generate a modulated signal for each band. The generated modulated signals are injected into the power line 8 by the signal injection unit 36.

[0033] 6 is a functional block diagram showing the demodulation process in the slave station 6. The demodulation process is mainly executed by the PLD 61 according to a program stored in advance in a memory or the like. The power waveform received by the receiver 60 is input to the demodulators 61F1 and 61F2. The demodulator 61F1 performs demodulation process in the F1 band, and the demodulator 61F2 performs demodulation process in the F2 band.

[0034] As shown in Fig. 6, the two frequencies ch1 / ch2 used in the F1 band are ch1: 5.0 kHz and ch2: 5.3 kHz. The two frequencies ch1 / ch2 used in the F2 band are ch1: 6.0 kHz and ch2: 6.3 kHz. In the demodulation units 61F1 and 61F2, the signals of the two frequencies ch1 / ch2 in the F1 band and F2 band, respectively, can be acquired in the orthogonal Q phase and I phase. If the signal power is represented as P, then P = {(Q phase) 2 +(I phase) 2} 1 / 2 It can be calculated as follows.

[0035] In the embodiment, the phase shift between signals is determined based on whether or not there is a phase shift with respect to a reference signal. Communication between a master station and a slave station is performed by repeating one communication sequence (protocol) as a unit. In the embodiment, the first signal in the communication sequence is used as a reference signal, and a phase shift is detected with respect to the phase of the reference signal.

[0036] In the modulation method of the embodiment, the demodulation process involves comparing the magnitude of the power spectrum of the channels to determine which channel is being used, and encoding the data by determining the phase shift from the reference signal.Furthermore, encoding is performed by analyzing the waveform patterns appearing in the Q phase and I phase.

[0037] Fig. 7 is a diagram showing phase changes. As shown in Fig. 7, in a situation where the phase is inverted every time a communication sequence is performed, the reference phase also changes every time. Therefore, instead of using an absolute 0° as the reference, the phase is changed relatively and the phase relative to the phase of the reference signal is detected. This has the advantage of being able to operate without having to adjust for the variations that exist in individual communication stations.

[0038] In the modulation method of the embodiment, the F1 / F2 reference frequency band and the ch1 / ch2 reference signal are transmitted every time a command is executed. This type of transmission format allows communication to be established with short-term timing adjustment. In addition, by determining the phase shift with respect to the reference signal, the phase is determined relative to the reference signal, and each station (master station, slave station) has an absolute 0° reference, so there is no need to worry about variations between stations. This makes it possible for each station to perform phase determination.

[0039] Fig. 8 is a diagram for explaining the phase determination. As shown in Fig. 8, the phase waveform can be determined by the sign that appears in the phase determination of each channel. That is, the following relationship exists. Same ch, same phase: The signs of the reference, Q phase, and I phase match. Same ch, different phase: The signs of the reference, Q phase, and I phase are reversed. Due to these characteristics, by analyzing the code of each phase, it is possible to identify the 0° / 180° of each of ch1 / ch2, and based on this identification result, it can be classified into four codes.

[0040] In other words, by transmitting signals from the parent station 3 to the child station 6 in two different frequency bands, for example F1 (ch1: 5.0 kHz / ch2: 5.3 kHz) and F2 (ch1: 6.0 kHz / ch2: 6.3 kHz), even if one frequency band cannot reach the child station due to standing waves, the other frequency band can reach the child station. This makes it possible to realize operation with increased robustness as a system.

[0041] Here, the master station 3 transmits two frequencies, F1 and F2, to the slave station 6, while the slave station 6 communicates with the master station 3 using, for example, only the F1 frequency. This simplifies the configuration of the slave station 6. In this case, by receiving at two points, the F side and the R side, the master station 3 can capture the signal at one side even if the signal does not reach the other side due to the influence of standing waves, etc.

[0042] Fig. 9 is a diagram for explaining synchronization to a reference signal. As shown in Fig. 9, in each frequency band, the master station 3 transmits a reference signal for each communication sequence. Since the slave station 6 transmits only at F1, it replies at the timing of F1 of the master station. When the slave station 6 receives a signal from the master station 3, it synchronizes its own signal with its own clock and replies. Similarly, the master station 3 also determines the phase of the slave station signal by taking its own (master station 3) clock timing from its own transmission timing.

[0043] By providing a clock with common specifications in both the master station 3 and the slave station 6, pseudo-synchronous communication can be realized without the need to send a synchronization signal over the communication line. In other words, by using the head signal as a trigger and taking timing with their own internal clocks, it is possible to create a state similar to that in which synchronization is established between the master station 3 and the slave station 6.

[0044] However, synchronization is performed on a command-by-command basis, and the timing is adjusted again each time a communication sequence is completed. The time required for this process is approximately a few power cycles, and it can be assumed that no excessive difference will occur.

[0045] Generally, in a power line carrier system, the power waveform looks different at the master station 3 and the slave station 6, which can cause a deviation in timing between the transmitting and receiving sides. This can cause the phase reference to shift, making phase modulation difficult. In the embodiment, the receiving station uses its own clock as a reference signal for counting the timing. This makes it possible to obtain processing timing without being affected by deviations caused by differences in how the waveform looks.

[0046] Figure 10 is a diagram showing an example of a communication sequence. The transmission format transmits ch1 and ch2 timing, the parent station address, and commands at frequencies F1 and F2, and assigns half a power cycle to a child station. By assigning a child station to a power cycle, the response time can be shortened. The circled numbers in the diagram indicate the chronological order.

[0047] In the embodiment, the signal from the slave station 6 is composed of one symbol. Therefore, even if the output period is made longer than the signal width actually used, there is no risk of interference with other signals. The signal output from the slave station 6 utilizes the overvoltage generated by opening the secondary side of the rubber transformer 5, so that the signal has the characteristic that the signal becomes larger as the signal length becomes longer.

[0048] Fig. 11 is a diagram for explaining an increase in a child station signal. As shown in Fig. 11, in the embodiment, a guard interval having a length of about 20% of the signal length is added before and after the signal section that is actually used. Since the signal often distorts at the rising and falling edges, providing a guard interval not only increases the signal output, but also makes it possible to improve the accuracy of signal extraction in the parent station 3.

[0049] As shown in Figure 11, by emitting a signal before and after the normal section in which the slave station 6 actually uses the transmission signal, the signal of the slave station with signal output restrictions can be made larger and more stable. This is because the overvoltage generated by opening the secondary side of the rubber transformer 5 is utilized. This allows for a larger signal volume and a more stable level, realizing higher quality communication, compared to generating the signal only in the required section.

[0050] As described above, in the embodiment, in an airport lighting monitoring and control system using power line carrier, communication between a master station and a slave station is realized by a modulation method that expresses four codes (00 / 01 / 10 / 11) using two frequencies and two phases. Since one signal can express four codes, it is possible to promote the aggregation of information, and thus improve responsiveness. In other words, it is possible to inject code information representing text into the lighting circuit, which promotes the highly information-based signaling and realizes faster control responsiveness. In addition, by using the power supply cycle as a synchronization signal, it is possible to simplify the signal configuration of the slave station signal, thereby improving noise resistance. Furthermore, simply changing the communication method does not require special measures such as rewiring power lines or replacing power supplies, and existing power line communication facilities can be reused.

[0051] As a result, according to the embodiments, it is possible to provide a light monitoring and control system, a master station, a slave station, and a communication method with improved responsiveness at low cost.

[0052] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0053] 1...power supply, 1-1...normal power supply, 1-2...standby power supply, 2...OP / C, 3...parent station, 4...bypass filter, 5...rubber transformer, 6...child station, 6A...processing unit, 6B...power line unit, 7...light, 8...power line, 9...control LAN, 10...parent unit, 11...monitoring desk, 12...aircraft detection sensor, 31...signal processing unit, 31F...modem unit, 31R...modem unit, 32...processor, 34...wave shaping unit, 35...amplification unit, 36...signal injection unit, 37...power waveform acquisition unit, 38...interface, 60...receiving unit, 61F1...demodulation unit, 61F2...demodulation unit, 62...processor, 63...sensor interface, 64...core breakage control unit, 65...transmission control unit, 66...transmission circuit, 67...signal acquisition unit, 68...power acquisition unit.

Claims

1. A lighting monitoring and control system in which the power lines supplying electricity to airport lights also serve as a communication medium, A transformer having a primary side connected to the power line and supplying power taken out from a secondary side to the lamp; A slave station provided between the secondary side of the transformer and the lamp; a master station that communicates with the slave station via the power line; The parent station includes: a modulation unit that generates a modulated signal by modulating a carrier signal having a frequency band of 10 kHz or less with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift; an injection unit that injects the modulated signal into the power line in synchronization with a power supply cycle of the power; The slave station, a receiver for receiving the modulated signal from a power waveform on the secondary side of the transformer; A demodulation unit that demodulates the received modulated signal to reproduce the code.

2. 2. The light monitoring and control system according to claim 1, wherein the modulation method is a modulation method in which a 2-bit code is associated with four symbols represented by two mutually different frequencies and phases.

3. the modulation unit modulates a plurality of carrier signals having different bands using the modulation method to generate a plurality of modulated signals having different bands; The light monitoring and control system according to claim 1 , wherein the injector injects the plurality of modulated signals into the power line.

4. a response signal generating unit, the slave station, generating a response signal by modulating a carrier signal with a response code to the demodulated code according to the modulation method; The light monitoring and control system according to claim 1 , further comprising: a transmitting unit configured to transmit the response signal to the master station via the power line.

5. the master station includes a control unit that repeatedly executes a transmission / reception sequence including transmission of the code from the master station to the slave station and transmission of the response code from the slave station to the master station; The light monitoring control system according to claim 4 , wherein the slave station includes a synchronization processing unit that uses a first signal in the transmission / reception sequence as a reference signal and synchronizes with the reference signal.

6. The light monitoring and control system according to claim 4 , wherein the transmitter transmits the response signal by an overvoltage generated by shorting / opening a secondary side of the transformer in synchronization with the power supply cycle.

7. The light monitoring and control system according to claim 4 , wherein the transmitting unit provides a guard interval before and after a signal section of the response signal.

8. A lighting monitoring and control system in which a power line that supplies power to airport lights also serves as a communication medium, comprising: a master station that communicates with a slave station connected to the light via the power line; a modulation unit that generates a modulated signal by modulating a carrier signal having a frequency band of 10 kHz or less with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift; and an injection unit for injecting the modulated signal into the power line in synchronization with a power supply cycle.

9. A light monitoring and control system in which a power line that supplies power to airport lights also serves as a communication medium, the light monitoring and control system comprising: A receiving unit that receives a modulated signal generated by modulating a carrier signal of a frequency band of 10 kHz or less with a multi-bit code by a modulation method that represents a symbol by a combination of a frequency shift and a phase shift from a power line that supplies power to the lamp; a demodulation unit that demodulates the received modulated signal to reproduce the code.

10. A communication method used in a light monitoring and control system in which a power line supplying power to an airport light also serves as a communication medium, in which a slave station connected to the light communicates with a master station via the power line supplying power to the light, The master station generates a modulated signal by modulating a carrier signal having a frequency band of 10 kHz or less with a multi-bit code using a modulation method that represents a symbol by a combination of a frequency shift and a phase shift; the master station injecting the modulated signal into the power line in synchronization with a power supply cycle; the slave station receiving the modulated signal from the power line; and the slave station demodulating the received modulated signal to recover the code.

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