U.S. patent application number 09/768302 was filed with the patent office on 2001-11-08 for system for monitoring airport equipments utilizing power-line carrier.
Invention is credited to Gotoh, Hidenori, Satoh, Takakazu.
Application Number | 20010038345 09/768302 |
Document ID | / |
Family ID | 26584308 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038345 |
Kind Code |
A1 |
Satoh, Takakazu ; et
al. |
November 8, 2001 |
System for monitoring airport equipments utilizing power-line
carrier
Abstract
A power-line carrier airport facilities monitor system,
comprising a host station and respective terminal for monitoring
individually the object facilities via a rubber transformer are
connected in series to a power line derived from a fixed current
generator, wherein the host station and respective terminal create
a control command for respective terminal/monitoring signal of the
object facilities as text data and, on the other hand, injections
said text data to the power line by FSK modulation based on the
zero cross detection of the power line power source waveform.
Inventors: |
Satoh, Takakazu; (Fuchu-shi,
JP) ; Gotoh, Hidenori; (Matsudo-shi, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Family ID: |
26584308 |
Appl. No.: |
09/768302 |
Filed: |
January 25, 2001 |
Current U.S.
Class: |
340/947 ;
340/951; 340/953; 340/958; 340/982 |
Current CPC
Class: |
H05B 47/185 20200101;
H05B 47/235 20200101; B64F 1/18 20130101; B64F 1/36 20130101 |
Class at
Publication: |
340/947 ;
340/951; 340/953; 340/958; 340/982 |
International
Class: |
G08G 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2000 |
JP |
2000-018892 |
Jun 9, 2000 |
JP |
2000-174059 |
Claims
1. An power-line carrier airport facilities monitor system, wherein
a host station connected to a higher order system and respective
terminal for monitoring individually the airport facilities via a
rubber transformer are connected in series to a power line derived
from a fixed current generator, said host station transmits control
signal to said respective terminal using power-line carrier based
on a signal from said higher order system, and said respective
terminal transmits the monitoring signal to said host station using
power-line carrier, wherein said host station and terminal
comprise; zero cross detection means for detecting the zero cross
of power source waveform of said power line; a data processing
calculation control section for creating a control command for
respective terminal/monitoring signal of the object facilities as
text data; and signal insert means for inserting said text data to
said power line by FSK modulation based on the zero cross detected
by said zero cross detection means.
2. An power-line carrier airport facilities monitor system, wherein
a host station connected to a higher order system and respective
terminal for monitoring individually the airport facilities via a
rubber transformer are connected in series to a power line derived
from a fixed current generator, said host station transmits control
signal to said respective terminal using power-line carrier based
on a signal from said higher order system, and said respective
terminal transmits the monitoring signal to said host station using
power-line carrier, wherein: said host station and terminal
comprise: zero cross detection means for detecting the zero cross
of power source waveform of said power line; a data processing
calculation control section for creating a control command for
respective terminal/monitoring signal of the object facilities as
text data; and signal insert means for inserting said text data
into said power line when a predetermined time has elapsed in the
same cycle, after the zero cross detection by said zero cross
detection means.
3. The power-line carrier airport facilities monitor system
according to claim 1 or claim 2, wherein: said host station
comprises means for creating several bytes of text data based on
said control command, and inserting said text data into said power
line by using zero crosses of a plurality of cycles of said power
source waveform; and said respective terminal comprises means for
creating 1-byte text data, which is monitoring signal of the
concerned object equipment, one terminal being allocated to each
cycle of said power source waveform, and for inserting said text
data into said power line using the zero cross of a predetermined
cycle of said power source waveform, after the reception of text
data power-line carried from said host station, when a
communication of said host station:terminal station=1:n is to be
performed.
4. The power-line carrier airport facilities monitor system
according to claim 1 or claim 2, wherein: the host station has a
display element connected via a current transformer to a bypass
filter provided between power lines derived from said fixed current
generator, and the status of said bypass filter is monitored by the
display status of this display element.
5. The power-line carrier airport facilities monitor system
according to claim 1 or claim 2, wherein: said respective terminal
is provided with a power accumulation element for accumulating
power of the power source section used at least for the lamp, and
the power accumulated in this a power accumulation element is used
at least during the signal injection by said signal injection
means.
6. A monitoring control system, wherein a host station and
respective terminal for monitoring and controlling the object to be
monitored respectively via a rubber transformer are connected in
series to a power line derived from a fixed current generator, said
host station transmits control signal to said respective terminal
using power-line carrier, and said respective terminal controls
said facilities to be monitored upon reception of said control
signal and, on the other hand, transmits the monitoring signal of
the facilities to be monitored to said host station using
power-line carrier, wherein: a filter apparatus comprising a LC
resonance circuit resonating with the frequency used for said
power-line carrier is provided on the output side power line of
said fixed current generator, and noise generated from said fixed
current generator and signal of the frequency used for said
power-line carrier between said host station and each terminal are
respectively separated.
7. The power-line carrier facilities monitor system according to
claim 6, wherein said filter apparatus comprises compensation
reactance elements for increasing respectively said host
station/respective terminal side impedance, installed at the power
line primary side positioned at said host station/respective
terminal side than said LC resonance circuit, in order to lower the
attenuation slope of the frequency used for power-line carrier due
to phasing or standing wave.
8. The power-line carrier facilities monitor system according to
claim 6, wherein said host stations comprises a plurality of signal
extraction sensors installed at the power line primary side
positioned at said host station/respective terminal side than said
LC resonance circuit in said bypass filter apparatus, in order to
taking in as reception signal the signal extraction sensor side
extraction signal presenting a higher reception level.
9. The power-line carrier facilities monitor system according to
claim 6, wherein an additional rubber transformer is connected to
said power line on this side of a specific terminal presenting a
deeper depression of reception level, among terminals connected to
said power line, in order to avoid the reception level depression
at said specific terminal.
10. The power-line carrier facilities monitor system according to
claim 6, wherein an additional rubber transformer is connected to
said power line on this side of a specific terminal presenting a
deeper depression of reception level, among terminals connected to
said power line, and a resonance circuit resonating with the
frequency used for the power-line carrier at the secondary side of
the connected additional rubber transformer, in order to avoid the
reception level depression at said specific terminal.
11. The power-line carrier facilities monitor system according to
claim 6, wherein said terminal is provided with a power charging
capacitor for charging power to the output side of the power line
modem out of signal injection period, when signal is injected to
said power line from the power line modem through a signal
injection reactance, and a switching element for short-circuiting
said signal injection reactance during said non signal injection
period, in order to increase the transmission power using said
charged power during signal injection.
12. The power-line carrier facilities monitor system according to
claim 11, wherein said switching element connects said signal
injection reactance before a predetermined time of the power source
waveform to inject signal, in order to avoid the generation of
overvoltage by the signal injection reactance.
Description
BACKGROUND OF THE INVENTION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2000-18892,
filed Jan. 27, 2000 and No. 2000-174059, filed Jun. 9, 2000, the
entire contents of which are incorporated herein by reference.
[0002] The present invention relates to an airport facilities
monitor system for monitoring airport facilities such as a number
of lamps, sensor or the like to be installed on runways, taxiways
or the like in the airport, the airport facilities monitor system
using the power-line carrier technology.
[0003] In the prior art, the airport facilities monitor system for
monitoring airport facilities constituted of a number of lamps,
sensor or the like to be installed in the airport using the
power-line carrier technology have a host station and, respectively
through a rubber transformer, terminals (slave stations) connected
in series to a power line derived from a fixed current generator
CCR/CCT (called fixed current generator, hereinafter) for creating
and generating a fixed current from a commercial alternative
current source, lamps and sensors being connected respectively to
these respective terminals.
[0004] There, both the host station and respective terminal perform
the host-terminal communication, by transmitting in combination
1-bit information synchronized with the cycle of the power source
waveform output from the fixed current generator. In short, the
host station transfers the control signal sent from a central
monitoring room side which is a higher order system to respective
terminal through a power line by the combination of 1-bit
information, and upon reception of this information, the respective
terminal control the turning ON/OFF of the lamp based on the
information contents. On the other hand, the respective terminal
monitors the lamp and sensor status, transfers its monitoring
information to the host station through the power line by the
combination of 1-bit information, while the host station is
constituted to transfer the monitoring information received from
respective terminals to a monitoring control panel, which is a
higher order system, through LAN, to display the status of lamps
and the like of respective terminals on an operator console.
[0005] By the way, in such power-line carrier monitoring control
system as mentioned above, in addition to a dedicated monitoring of
burnt-out lamp, nothing but a predetermined number of lamps can be
monitored and controlled, because little data amount can be treated
by the power-line carrier and, besides, the transfer rate is
low.
[0006] On the other hand, the fixed current generator in the
aforementioned monitoring and control system, is the one designed
to supply the power line with power of fixed current and, more
concretely, as shown in FIG. 1, adopts a method to select a current
waveform S2 of high amplitude between a low amplitude current
waveform S1 and the high amplitude waveform S2 through the phase
control at a convenient phase angle (60 degrees for example) from
the zero cross point of the low amplitude current waveform S1,
using a thyristor, output a predetermined fixed current (6.6 A for
example) defined beforehand to be used for lamps or other airport
equipment, and supply to the power line.
[0007] Therefore, the current immediately after the phase control
varies generally in a rapid rise state, presents a high frequency
equal or superior to 50 Hz/60 Hz in respect of frequency, transits
to a standard waveform (sinusoidal wave) of 50 Hz/60 Hz when in
attains the high amplitude current waveform, but happens to be
unstable immediately after this transition.
[0008] There, conventionally, in the case of transfer of a required
signal using a power-line carrier, control, monitoring or other
signals are transferred using the power-line carrier, by modulating
them with a predetermined frequency from a power line mode which is
a part of signal processing system, for the high amplitude waveform
S2 at such a timing to avoid the low amplitude current waveform on
the power line and rapid rise portions immediately after the phase
control, and further, unstable portions during the transition to
the high amplitude current waveform, namely noise producing
portions.
[0009] However, the aforementioned monitoring and control system
aims only to transfer the signal at an appropriate timing, noise
still generates from the fixed current generator by the phase
control, and under the influence of this noise, the reception
sensibility of host station and respective terminal deteriorates
considerably. In addition, this noise is a spike noise generated
like as impulse, and moreover, it is extremely difficult to
eliminate, as the noise generation point varies according to the
tap position (phase control angle) adjusting the lamp
brightness.
[0010] Also, in the host station and respective terminal, the
control signal and monitoring signal are carried by the power line,
using a power line circuit including power line, rubber transformer
or the like; however impedance due to LC exists in the power line
circuit, and this impedance absorbs signal carried by the power
line. This is caused mainly by resonance phenomenon between the
rubber transformer reactance L component and the power line and
ground capacitance, and there exist abnormal attenuation points of
signal carried by the power line. As the result, terminals at the
position corresponding to the abnormal attenuation point drop
remarkably in their reception sensibility due to the attenuation of
carried signal.
[0011] Especially, in the case of power-line carrier, abnormal
attenuation point is an inevitable problem, because rubber
transformers constituting a number of reactance components are
installed in the power line circuit. And further, the installation
of rubber transformer being dependent on the lamp location in the
airport, and can not be decided arbitrarily, the abnormal
attenuation amount increases inconveniently according to the
installation mode.
BRIEF SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
power-line carrier airport facilities monitor system for allowing
to transfer stably host station control signal and status signal of
lamp, sensor and the like of a number of terminals, and allowing to
transfer effectively a quantity of data.
[0013] Another object of the present invention is to provide a
monitoring control system using the power-line carrier for reducing
the effect of noise produced by the fixed current generator, and
also to ensure a high quality transfer, without being influenced by
the power line circuit construction conditions.
[0014] To solve the aforementioned problems, the present invention
relates to a power-line carrier airport facilities monitor system,
wherein a host station and respective terminals for monitoring and
controlling individually the object facilities such as lamp, sensor
and the like respectively via a rubber transformer are connected in
series to a power line derived from a fixed current generator, the
host station transmitting to the respective terminal using
power-line carrier based on a control signal from a higher order
system, while the respective terminals transmitting the monitoring
signal from the object facilities to the host station using
power-line carrier, wherein the host station and terminal
comprise:
[0015] zero cross detection means for detecting the zero cross of
power source waveform of the power line, a data processing
calculation control section for creating a control command for
respective terminal/monitoring signal of the object facilities as
text data, and signal insert means for inserting the text data to
the power line by FSK modulation based on the zero cross detected
by the zero cross detection means.
[0016] According to the invention, adopting the aforementioned
configuration, it is possible to avoid the prevention magnetic
saturation, the text data to be inserted into the power line is
transmitted by frequency modification, and as this frequency
modulation, it is transmitted by FSK modulation using two frequency
modulation, allowing to transmit avoiding stationary noise
generated by the fixed current generator (CCR/CCT) creating a fixed
current from the commercial power source, and to realize a stable,
and, appropriate power-line carrier of the text data without being
affected by the noise.
[0017] Also, to solve the aforementioned problems, the present
invention relates to a monitoring control system using power-line
carrier, wherein a host station and respective terminals for
monitoring and controlling the facilities to be monitored
respectively via a rubber transformer are connected in series to a
power line derived from a fixed current generator, the host station
transmitting a control signal from a higher order system to the
respective terminal by power-line carrier, while the respective
terminals monitors the facilities to be monitored upon reception of
the control signal and, at the same time, transfers a monitoring
signal of this facilities to be monitored by power-line carrier,
wherein a bypass filter apparatus comprises a LC resonance circuit
resonating with the frequency used for the power-line carrier is
provided on the output side power line of the fixed current
generator, and noise generated from the fixed current generator and
signal of the frequency used for the power-line carrier between the
host station and each terminal are respectively separated.
[0018] The present invention, adopting the aforementioned
configuration, installs a filter apparatus including a LC resonance
circuit resonating the frequency used for the power-line carrier
and sends noise generated from the fixed current generator to the
power source generation side by the filter apparatus, and on the
other hand, sends signal transmitted and received between the host
station and the terminal to the host station and terminal side by
means of the filter apparatus, thus separates noise and signal
completely, improving the signal transfer quality.
[0019] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0020] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments give below, serve to explain the principles
of the invention.
[0021] FIG. 1 is a diagram illustrating an example of power source
waveform changeover by phase control by a fixed current
generator;
[0022] FIG. 2 is a general configuration example diagram of the
power-line carrier airport facilities monitor system according to
the present invention;
[0023] FIG. 3 is a configuration diagram showing an embodiment of
the host station and respective terminal, in the power-line carrier
airport facilities monitor system according to the present
invention;
[0024] FIG. 4 illustrates an example of communication of the whole
system;
[0025] FIG. 5 illustrates the signal delivery between a monitoring
control panel of a higher order system and the host station;
[0026] FIG. 6 illustrated a signal delivery area of the host
station and the respective terminal;
[0027] FIG. 7 is a diagram showing the signal allocation of the
host station and the respective terminals for waveform;
[0028] FIG. 8 is a time chart illustrating the signal insertion of
the host station and the respective terminal avoiding noise of
waveform;
[0029] FIG. 9 is a diagram illustrating the cause of noise
generation in the waveform;
[0030] FIG. 10 is a general configuration diagram showing an
example of airport lamp monitor system according to the present
invention;
[0031] FIG. 11 is a diagram showing the noise generation state of
the power source waveform generated from the fixed current
generator;
[0032] FIG. 12 is a configuration drawing showing a bypass filter
apparatus inserted into the power line in the vicinity of the
output side of the fixed current generator;
[0033] FIG. 13 is a configuration diagram showing the relation
between the filter apparatus and the host station side signal
injection/signal extraction;
[0034] FIG. 14 is a configuration diagram of respective terminal to
be connected to the power line;
[0035] FIG. 15 is a diagram illustrating the reception level
depression due to phasing, standing wave at respective terminal
connection position;
[0036] FIG. 16 represents an equivalent circuit of power line and
rubber transformer;
[0037] FIG. 17A and FIG. 17B illustrate the influence state of
phasing or the like of the host station receiving signal from
respective terminal;
[0038] FIG. 18 is a diagram showing an example of compensation
means for increasing the lamp side impedance;
[0039] FIG. 19 is a configuration diagram illustrating the
reception duplication at the host station;
[0040] FIG. 20 is a diagram showing another example of compensation
means for increasing the lamp side impedance;
[0041] FIG. 21 is a state diagram of the reception level from
respective terminal in the host station;
[0042] FIG. 22 is a processing flow chart of reception duplication
at the host station;
[0043] FIG. 23 is a configuration diagram compensating the
reception level depression at the terminal;
[0044] FIG. 24 is a configuration diagram showing an embodiment of
power economy out of signal transmission period of time in
respective terminal; and
[0045] FIG. 25 illustrates the power economy out of signal
transmission period and the timing in the signal transmission
period in respective terminal.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Hereafter, embodiments of the present invention will be
described referring to drawings.
[0047] FIG. 2 is a general configuration diagram showing an example
of the power-line carrier airport facilities monitor system
according to the present invention.
[0048] This airport facilities monitor system comprises a central
monitoring room (called higher order system, hereinafter) 3
including an operator console 1 performing the operation status
display of taxiway central line lamp L1, stop bar light L2, runway
lamp L3 (collectively called lamp L, hereinafter) sensors C or the
like, turning on/off control of lamp L, operation test of
respective terminal, reset or other operation of respective
terminal, and a monitoring control panel 2 or the like connected to
this console 1 via a control LAN, and mutually transmits and
receives signal to and from the operator console 1, a host station
7 including a fixed current generator 4 such as CR/CCT which is a
fixed current generator for creating and outputting a fixed current
from a commercial alternative power source, and a host station
control panel 6 connected to a power line 5 derived from this
generator 4 via a transformer for collecting the operation status
of various lamps L and monitor signals that are signals of various
other sensors C informing the higher order system 3 of them, or
transmitting control signal from the higher order system 3 to
respective terminal 8 via the power line 5, and respective
terminals (slave stations) 8 connected similarly to the power line
5 in series via a rubber transformer 9 respectively, for monitoring
individually the status of respective lamp L or sensor C and
controlling turning on/off of the lamp L.
[0049] Besides, the monitoring control panel 2 is the one managing
collectively various power line circuit information, is connected
to the transfer host station 7 supervising a single power source
circuit via a transfer LAN, and has a function to own individual
power line circuit information jointly with the transfer host
station 7.
[0050] FIG. 3 shows a concrete configuration diagram showing a
transfer host station 7 and a single terminal 8 connected in series
to a power source apparatus which is an airport illumination system
derived from a fixed current generator 4 and a power line 5 serving
as communication media in charge of power-line carrier. It goes
without saying that a number of terminals 8 are connected to the
power line 5.
[0051] Namely, a host station control panel 6 of the host station 7
and, a number of terminals 8 individually via a respective
transformer 9 are connected to the output side of the fixed current
generator 4, as mentioned above.
[0052] This host station control panel 6 comprises a filter unit
11, a data processing calculation control section 12, a signal
injection section 13 for transmitting control signal to respective
terminal 8, a signal extraction section 14 for receiving operation
status signal of the lamp L, sensor C and the like.
[0053] The filter unit 11 comprises, a bypass filter 11a of LC
resonance circuit constituted of a coil L and a capacitor C, for
preventing harmonic noise from the fixed current generator 4 from
entering the host station control panel 6, respective terminal 8
side and for cutting a specific frequency used for the power-line
carrier output from the host station control panel 6, respective
terminal 8 side and preventing from entering the fixed current
generator 4, a bypass filter status confirmation circuit for
displaying for instance on a LED display element 11b the current
flowing state through a current detection sensor current
transformer CT, a host station dedicated CT11c for injecting
information concerning the control from the higher order system 3
to the power line 5 based on the zero cross detection timing of the
power source waveform of the fixed current generator 4, and a
extraction current transformer lid for extracting the monitoring
signal representing the status of the lamp L, and sensor C of the
terminal 8 from the power line 5, or the like.
[0054] The data processing calculation control section 12 has a
function to create a text data based on the control signal for
respective terminal transferred from the higher order system 3, and
to transfer the monitoring information from the respective terminal
to the higher order system.
[0055] The signal injection section 13 comprises a timing
generation circuit 13a for taking in and outputting the text data
created by the data processing calculation control section 12 at a
predetermined timing after the zero cross detection of the power
source waveform output from the fixed current generator 4, a power
line modem 13b for transmitting the text data by two specific
frequencies submitted to the frequency shift modulation (FSK)
according to the timing from this timing generation circuit 13a,
and a transmission amplification element 13c for amplifying data
output from this power line modem 13b and injecting in the power
line 5 through the host station dedicated CT11c.
[0056] The signal extraction section 14 comprises zero cross
detection means 14a for detecting zero cross of the power source
waveform from the extraction current transformer lid through a
passive filter, a reception amplification element and an active
filter, and signal detection means 14db including a timing
generation circuit 13a for taking in the text data extracted from
the extraction current transformer 11d similarly through the
passive filter, the reception amplification element and the active
filter at a predetermined timing after the zero cross detection of
the power source waveform output by the zero cross detection means
14a.
[0057] Next, the respective terminal 8 is connected between the
rubber transformer 8 connected to the power line and the lamp
L/sensor C, and constituted of various forms, such as being
connected only to the lamp L, or connected only to the sensor C,
further connected to the lam L and the sensor C, according to its
application.
[0058] The respective terminal 8 comprises a lamp power source
system 21, a data processing calculation control section 22
constituted of a CPU for creating a text data by taking in the
status and lamp L and the like connected to this lamp power source
system 21 and the other necessary signals, controlling the lamp L
based on the text data received from the host station 7 through the
power line 5, and further performing necessary processing according
to the command from an external equipment or input equipment, a
signal injection section 23, and a signal extraction section
24.
[0059] The lamp power source system 22 comprises a power source
section 21a, a transformer 21b for taking out power supply for the
operation of its own terminal, various protection circuit 21c for
protecting the lamp L, an ON/OFF control section 21d such as triac
for controlling the light-off, a current detection section 21e for
detecting an overcurrent, a burnt-off lamp detection circuit 21 f
for detecting a burnt-out lamp L and the like, and these detection
signals are sent to the data processing calculation control section
22.
[0060] The signal injection section 23 comprises a timing
generation circuit 23a for taking in and outputting the text data
created by the data processing calculation control section 12 at a
predetermined timing after the zero cross detection of the power
source waveform output from the fixed current generator 4, a power
line model {modem?} 23b for transmitting the text data by two
specific frequencies submitted to the frequency shift modulation
(FSK) according to the timing from this timing generation circuit
13a, and a transmission amplification element 23c for amplifying
data output from this power line modem 23b and injecting in the
power line 5.
[0061] The signal extraction section 24 comprises zero cross
detection means 24a including a timing generation circuit 23a for
detecting zero cross of the power source waveform output from the
fixed current generator 4, and signal detection means 24 including
a timing generation circuit 23a and a data processing calculation
control section 111 has a function to receive a control signal for
respective terminal 109 transferred from the higher order system
103, to create text data in addition to a passive filter, a
reception amplification element and an active filter such as low
pass, band pass or the like.
[0062] In addition, as a number of terminal 8 are connected to a
power line 5 derived from a single fixed current generator 4, the
signal attenuates more, the longer is the distance of this total
power line 5, and the higher is the number of terminals. The signal
output level can be increased to extend the signal range distance;
however, it is not allowed to consume much power for the terminal
signal output, because the power source capacity of the airport
illumination equipment is limited. There, as for the signal
injection method of respective terminal, the apparent power source
consumption can be reduced by accumulating power out from a power
source section 21b beforehand while waiting for signal insertion in
a power accumulation element 27, and supplying power accumulated in
the power accumulation element 27 during the signal insertion and
transmission.
[0063] Besides, the filter unit 11 comprises a bypass filter which
is a resonance circuit of coil and capacitor, and a bypass status
confirmation circuit, and in this bypass status confirmation
circuit, as high voltage is accumulated in a capacitor C of the
bypass filter, it becomes possible to take measures for the
security by displaying the status of this bypass filer on a display
element 11b and informing the higher order system 3.
[0064] Next, the outline of data communication will be described
referring to FIG. 4, before explaining the operation of the
aforementioned system.
[0065] First, in the higher order system 3, the monitoring control
panel 2 receives monitoring signal representing the status of lamp
L and sensor C transferred from the host station 7, transmits to
the operator console 1, and displays the operation status of lamps
or the like. In addition, the console 1 of the higher order system
3 inputs necessary control commands from an operator, sends
controls signals for on/off control of the lamp L, operation test
of respective terminal, reset of respective terminal or the like to
the respective terminal 8 through the monitoring control panel 2
and the host station 7, and the operator console 1 monitors
collectively the response status of this terminal side, and,
performs the control.
[0066] Normally, one host station 7 is connected to one fixed
current generator, and the host station control panel 6 transmits
and receives signals with the higher order system 3/respective
terminal 8, and transmits signal to the requiring higher order
system/lower order terminal 8.
[0067] In short, a mutual and ordinary monitoring is performed (S1)
as shown in FIG. 4, between the host station 7 and the respective
terminal 8, and the monitoring control panel 2 acquires data from
the host station control panel 6 when the host station is normal
(healthy counter UP).
[0068] Besides, the host station control panel 6 suspends
temporarily the control, upon reception of a control command (S2)
from the higher order system 3 during the ordinary monitoring with
the respective terminal 8, perform the terminal control by
interruption to the respective terminal 8 (S3) and sustains the
ordinary monitoring after performing this control.
[0069] The communication between the monitoring control panel 2 and
the host station 7 is performed according to the procedures as
shown, for example, in FIG. 5. In short, the monitoring control
panel 2 and the host station 7 are provided with a transfer area
such as monitoring control panel area (upper stage) or host station
area (lower state), and has a mechanism to output control commands
each time it is necessary.
[0070] In other words, ordinarily, as monitoring commands are
written in the communication from the monitoring control panel 7
shown in the upper stage to the host station 7, the host station
monitors the respective terminal 8, based on this ordinary
monitoring command, collects the monitoring status of respective
terminal, and stores in a necessary memory area.
[0071] In this state, the monitoring control panel 7, when a
control is required, writes a control command code as command to
the host station 7, and, writes control contents such as necessary
terminal address or command (request contents) and the like.
[0072] Here, as shown in the lower stage of the same drawing, the
host station 7 sequentially performs the command control contents
under the sequential terminal address, to the respective terminal,
based on the command from the monitoring control panel 2. There,
after the execution of the control contents to the respective
terminal, a control completion flag is set, and on the other hand,
the monitoring control panel 2 is informed of this control
completion. Here, the monitoring control panel 2, sets to the
ordinary monitoring state by writing again an ordinary monitoring
command to the host station 7, and erases the control completion
flag.
[0073] By the way, on the host station 7 side, as shown in FIG. 3,
a current detection current transformer CT is disposed between a
coil L-capacitor C of the bypass filter 11a for avoiding mutual
imprecations of harmonic noise generated from the fixed current
generator 4 side and power line carrier superposed on the power
line 5 from the terminal side or the like, the operation status of
the bypass filter 11a can be monitored at all times by connecting a
LED display element 11b to this current transformer CT. In short,
when the bypass filer 11a is normal, the display elements 11
repeats the blinking according to the commercial frequency 50/60 Hz
output from the fixed current generator 4, when charge remains in
the capacitor C of the filter 11a, the display element 11b
continues to emit light, and on the other hand, when the capacitor
C is abnormal, the display element 11b is extinguished.
[0074] Now, electric shock or other accidents can be prevented
beforehand and exhaustively and it is effect for measures in
respect of the security to inform the higher order system 3 of
abnormality information by artificially monitoring the display
information of the display element 11b, or monitoring by taking in
the data processing calculation control section 12.
[0075] Further, the communication between the host station 7 and
the respective terminal 8 shall be a method wherein the host
station 7 is set as primary station, to perform the communication
to the respective terminal 8. In case of monitoring at all times,
as shown in FIG. 6, it is so constituted to allocate 3-byte
information constituted of start STX, command CMD and address ADR
from the host station 7 to the terminal 8, and to allocate 1 byte
to the status information of lamp, sensor, its own terminal
information or the like from the terminal 7 to the host station
8.
[0076] Besides, in this method, a simultaneous control of a
plurality of terminals 8, . . . is made possible and the data
transfer effectiveness is secured by performing host station
7.fwdarw.terminal 8 one-way communication for control commands such
as turning on/off of the lamp L, and further, by including a group
designation address in the address ADR.
[0077] FIG. 7 is a drawing illustrating an example of information
allocation for the power source waveform for reducing the
monitoring interval, and increasing the monitoring efficiency.
[0078] In this example, when the host station 7 generates a control
command, the zero cross is detected by zero cross detection means
14a for each half cycle/1 cycle of the power source waveform of the
power line 5 taken out from a current detection sensor current
transformer lid, and this detection timing signal is sent to a
timing generation circuit 13a.
[0079] At this time, as 3-byte information constituted of start
STX, command CMD and address ADR is created in the data processing
calculation control section 12 upon reception of the higher order
system 3 or the like, as shown in FIG. 6, start STX, command CMD
and address ADR are taken in for respective zero cross detection
timing signal, and injected sequentially into the power line 5,
through frequency shift modulation (FSK) by a power line modem
section 13b.
[0080] At this time, in the case when the address ADR includes, for
instance, an address of simultaneous control command of a plurality
of necessary terminals 8, these terminals 8 extracts sequentially
3-byte information from the host station 7 received by the timing
generation circuit 23a through the signal detection means 24b,
based on the zero cross timing signal generated each time when the
zero cross detection means 24a detects a zero cross, and sends to
the data processing calculation control section 22. Here, the data
processing calculation control section 22, in case of judging that
it relates to its own terminal from the received address, creates
and outputs the status of the concerned terminal corresponding to
the command contents in text data format, then the timing
generation circuit 23a sends the text data to the power line modem
section 23b, based on the zero cross detection timing signal from
the fifth cycle predetermined for each terminal, after the
detection of start STX, and injects into the power line 5 by
frequency shift modulation (FSK).
[0081] At this time, the host station 7 prepares a buffer area for
each cycle, counts power source waveform zero crosses after the
transmission of start STX, provides an answer area of respective
terminal for the fifth cycle and thereafter, judges the presence of
status signal from respective terminal, sets "1" to the
corresponding bit area in the buffer in case of status signal
presence, receives sequentially text data from respective terminal
8, and stores sequentially for instance in another reception area
of the buffer. This text data is acquired as respective terminal
status information based on the turn of "1" in the order of bit in
the buffer, and transferred to the higher order system 3. Besides,
the lowest stage of the same drawing shows data presence/absence
status in the buffer.
[0082] FIG. 8 illustrates the signal injection timing from the host
station 7 and respective terminal 8.
[0083] Ordinarily, the fixed current generator 4 is the one to
supply the power line 5 with a fixed current power, and more
specifically as shown in FIG. 9, is the one for outputting a fixed
current of, for instance 6.6 A determined beforehand to be used for
the airport facilities, by changing over to and selecting a high
amplitude current waveform S2 at the changeover point of a
predetermined phase angle, for instance 60 degrees, from the zero
cross point of a low amplitude current waveform S1, using a
thyristor, between the low amplitude current waveform S1 and the
high amplitude current waveform S2, resulting in noise generation
in the proximity of the changeover point.
[0084] There, when the host station 7/respective terminal 8 inject
signal into the power line 5, in order to avoid noise generated
from the fixed current generator 4, they inject signal, at a timing
sufficiently remote from the changeover point within the power
source waveform cycle shown in FIG. 8, in short, after an interval
of a predetermined period of time T from the zero cross.
[0085] To be more specific, both host station 7/respective terminal
8 detect the power source waveform zero cross by the zero cross
detection means 14a/24a, and the data processing calculation
control section 12 of the host station 7 inserts 3-byte information
text data to the power line 5 through the power line modem section
13b within the transmission request period under the control
command from the higher order system 3, and at this time, 3-byte
information made as text data is sequentially inserted and
transmitted by the power line modem section 13b, when a
predetermined time T has elapsed from the zero cross by the timing
generation circuit 13a.
[0086] The respective terminal 8 also, similarly, counts the power
source waveform zero cross, after the reception of start STX,
provides an answer area of respective terminal for the fifth cycle
and thereafter, and also, when a predetermined time T has elapsed
after the zero cross detection by the timing generation circuit
23a, 1-byte information which is status information of lamp or the
like made as text data is inserted into the power line 5 through
the power line modem section 23b and transmitted.
[0087] Consequently, according to the aforementioned embodiment, as
the text data to be inserted into the power line is transmitted by
FSK modulation using two frequencies, the transmission can be
performed avoiding stationary noise generated from the fixed
current generator 4, allowing a stable, and appropriate text data
power-line carrier without being affected by noise.
[0088] In addition, the signal insertion section 13, 23 transmits
text data avoiding the point where noise is generated from the
fixed current generator 4 in a predetermined cycle as shown in FIG.
8, allowing to improve the transfer quality, and eventually,
enhance the signal detection accuracy of the other party.
[0089] Further, the host station creates 3-byte text data based on
the control signal and inserts into the power line 5 using power
source waveform zero cross of a plurality of cycles as shown in
FIG. 7, and on the other hand, the respective terminal 8 creates
1-byte text data, namely monitoring signal of the object equipment,
and inserts into the power line 5 using power source waveform zero
cross of a predetermined cycle, permitting to transfer a quantity
of data even when a low transfer rate power line modem is used.
[0090] Moreover, the host station 7 monitors the status of the
bypass filter 11a, by disposing a display element 11b on the bypass
filter 11a installed between power lines through a current
transformer CT, allowing to prevent electric shock or other
accident beforehand, by informing the higher order system 3 of the
bypass filter abnormality. Further, the respective terminal 8,
being provided with a power accumulation element 27 for
accumulating power of the power source section 21a of the lamp L,
permits to use effectively the power accumulated while waiting
signal insertion for signal insertion, and to intend to reduce the
power consumption.
[0091] As mentioned above, the present invention converts host
station control signal and status signal of monitored equipment of
a number of terminals into a text data, and at the same time,
transfers by a specific frequency or, further transfer the text
data all the way avoiding noise, resulting in a stable transfer
free from noise influence.
[0092] In addition, according to the present invention, the host
station transfers several bytes of text data over a plurality of
cycles of the power source waveform, while the respective terminal
transfer sequentially to the host station 1-byte text data for
every 1 cycle of a predetermined waveform, allowing to transfer
effectively a quantity of data concerning the monitoring
control.
[0093] Next, another embodiment of the present invention will be
described referring to FIG. 10.
[0094] FIG. 10 is a general configuration diagram showing an
example of the power-line carrier airport facilities monitor system
according to the present invention. This monitor control system
comprises various lamps L as equipment in the airport, a central
monitoring room (hereinafter, called higher order system) 103
including an operator console 101 performing the operation state
display of sensors C or the like, control of lamp L turning ON/OFF,
operation test of respective terminal, reset or other operation of
respective terminal, and a monitoring control panel 102 or the like
connected to this console 101 via a control LAN, and mutually
transmits and receives signal to and from the operator console 101,
and the like, a fixed current generator (CCR) 104 generating and
outputting a fixed current from a commercial alternative power
source, a filter apparatus 106 having a bypass filter function
provided at a position relatively near {near} the output side of
the fixed current generator 104 among power lines 105 derived from
this fixed current generator 104, a host station 108 connected from
this filter apparatus 106 via a host station dedicated transformer
(current injection/extraction sensor) 107 for collecting the
operation state of various lamps L, . . . and monitor signals that
are signals of various other sensors C, informing the higher order
system of them, or transmitting control signal from the higher
order system 103 to respective terminal 109 via the power line 105,
and respective terminals (slave stations) 109 connected to the
power line 105 in series via a rubber transformer 110 respectively,
for monitoring individually the state of respective lamps L or
sensor C and executing the control of lamp L ON/OFF upon the
reception of control signal from the host station side.
[0095] Besides, the monitoring control panel 102 is the one
managing collectively various signals concerning various power line
circuits, is connected to the host station 108 supervising a single
power source circuit 104 via a transfer LAN, and has a function to
own individual power line circuit signal jointly with the transfer
host station 108.
[0096] The fixed current generator 104 adjusts the brightness of
the lamp L by changing the total current value through the phase
control as a convenient phase angle as shown in FIG. 15, using a
thyristor (not shown). The phase angle for this phase control is
changed to approach 0 degree side brighter is the lamp L and 180
degrees side darker is the lamp L, however the phase angle to be
phase controlled may vary according to the system scale. Here, when
the phase control is executed, the waveform shows a rapid rise
after the phase control, the frequency of this rise section becomes
higher than the commercial frequency, and after the rise, a
vibration noise is generated as shown by beta .beta..
[0097] The filter apparatus 106 is provided with an I type LC
resonance circuit for respective frequency, so as to separate a
specific frequency used for power-line carrier in the host station
102 and respective terminal 109 from the fixed current generator
side (power source side). For instance, in the case of FSK
modulation and power-line carrier of a required signal by a power
line mode composing the transmission system of the host station 102
and respective terminal 109, as two frequencies Fa, Fz are used, an
I type L1/C1 resonance circuit resonating Fa and an I type L2/C2
resonance circuit resonating Fz are connected in series between
power lines as shown in FIG. 12.
[0098] By the way, in the case where the aforementioned LC
resonance is not operated normally, signal can not be received
between the host station and the terminal; therefore, fault
detection current sensor CT1, CT2 are interposed between L1 and C1,
and between L2 and C3 respectively through a fuse F1, F2. The
secondary side of this current sensor Ct1, and CT2 is introduced,
for instance, in the host station 108 or the like. Consequently, in
the case of short-circuiting of the capacitor C1, C2, a large
current flow breaks the fuse F1, F2, and the current does not flow
to the sensor CT1, CT2 allowing to detect the fault of the LC
resonance circuit. In the case of open failure of the capacitor C1,
C2 also, the fault of the concerned resonance circuit can be
detected.
[0099] The host station 108 is connected to a filter apparatus 106
interposed on the power line 105 through a host station dedicated
transformer (CT11, CT12) 107 and, therein, a data processing
calculation control section 111 constituted of CPU, a power line
modem 112, a signal injection section 113 and signal extraction
section 114 or the like are disposed as shown in FIG. 13.
[0100] This data processing calculation control section 111 has a
function to receive a control signal for respective terminal 109
transferred from the higher order system 103, to create text data
for example, and also to convert monitoring signal from respective
terminal 109 into transferable data, and transfer to the higher
order system 103.
[0101] The power line modem 112 receives, for instance, a
predetermined timing instruction obtained from the power source
waveform on the power line, and outputs a control signal, for
example, converted into text data, by performing frequency shift
modulation (FSK). Here, this power line modem 112 is not limited to
FSK modulation using two frequencies, but it may by AM modulation,
PSK modulation or tone burst method, using a single frequency.
[0102] The signal injection section 113 injects the control signal
subjected to frequency shift modulation by the power line modem 112
to the power line 105 through a transmission amplification element
114, a CR resonance circuit 115, a blocking coil 116 and a
transformer CT 11 in the filter apparatus 106, or the like.
[0103] The signal extraction section 114 is the one for extracting
signal carried by the power line, and comprises a transformer CT12
in the filter apparatus 106, and an open protection resistor 117,
for example a passive filter, a reception amplification element 119
and the like.
[0104] The respective terminal 109 is connected to the power line
105 respectively through a rubber transformer 110 and concretely,
has a configuration as shown in FIG. 14.
[0105] In short, each terminal 109 comprises a lamp power source
system 121, a data processing calculation control section 122
constituted of a CPU for taking in the state of lamps L or the like
connected to this lamp power source system 121 for creating a text
data, for controlling the lamp L based on the text data received
from the host station 108 through the power line 105, and further,
for performing necessary processing according to instructions from
an external equipment of input equipment, a signal injection
section 123, and a signal extraction section 124.
[0106] The lamp power source system 121 comprises a power source
section 121a for generating a power source for the operation of its
own terminal, a current transformer 121b for taking out the power
source for the operation of its own terminal, various protection
circuits 121c for protecting the lamp L, an ON/OFF control section
121d such as triac for controlling the turning on/off of the lamp
L, a current detection section 121e for detecting overcurrent, and
a lamp filament rupture detection circuit 121f for detecting the
filament burn-out of the lamp L and the like, and these detection
signals are sent to the data processing calculation control section
122.
[0107] The signal injection section 123 includes a timing
generation circuit 123a for taking in and outputting the text data
created by the data processing calculation control section 122 at a
predetermined timing after the detection of zero cross of power
source waveform outputted from the fixed current generator 104, a
power line modem 123b for transmitting the text data at frequency
shift modulated (FSK) two specific frequency, a transmission
amplification element 123c for amplifying the signal output from
this power line model {modem?} 123b, and a signal injection
reactance 123d for injecting signal to the power line 105.
[0108] The signal extraction section 124 is constituted of zero
cross detection means including the timing generation circuit 123a
detecting the zero cross of power source waveform output from the
fixed current generator 104, a passive filter, a reception
amplification element, an active filter such as low pass, band pass
or the like, and further a timing generation circuit 123a and
signal detection means 123b including a data processing calculation
control section 122.
[0109] Now, the operation of the monitoring control system as
mentioned above will be described referring to drawings.
[0110] First, as a general operation of monitoring control system,
the monitoring control panel 102 receives lamp L and sensor C
monitoring signal transferred from the host station 108, transmits
to the operator console 101, and displays the operation state of
lamps, or the like. In addition, the console 101 of the higher
order system 103 inputs necessary control instructions from the
controller, sends control signals such as lamp L turning ON/OFF
control, respective terminal operation test, respective terminal
reset or the like to the respective terminal 109 through the
monitoring control panel 102 and the host station 108, monitors
collectively the response state of this terminal side by the
operator console 101 and, at the same time, performs the
control.
[0111] The host station 108 is, normally, connected one by one to a
single fixed current generator 104, transmits and receives signal
between the higher order system 103/respective terminal 109 and
transfers necessary signal to the higher order system 103/lower
order terminal 109.
[0112] In short, the host station 108, becoming the primary
station, takes in control signal or the like transferred from the
higher order system 103, edits to for example text data necessary
for the data processing calculation control section 111,
thereafter, sends to the power line modem 112 at a predetermined
timing based for instance on a signal from the power line 105. This
power line modem 112 FSK modulates the text data, injects into the
power line 105 through the filter apparatus 106, and transfers to
requiring terminal 109.
[0113] The respective terminal 109 detects the zero cross of power
source waveform through the rubber transformer 110 and the power
source CT21b, predicts the superposition period of the text data to
be superposed to the power source waveform beforehand by the timing
generation circuit 123a, takes in the text data to be superposed to
the power source waveform extracted by the signal extraction
section 124 during this prediction period, and sends to the data
processing calculation control section 122, as shown in FIG. 14.
This calculation control section 122 controls the lamp L turning
on/off by controlling the ON/OFF control section 121, when it
judges that the control signal is addressed to it-self from the
text data.
[0114] By the way, in general, the power line circuit including the
power line 105 and the rubber transformer 110 has a closed loop
configuration, and the reception level of frequencies used for
power-line carrier varies according to the power line connection
position of the terminal as shown in FIG. 15. In short, a slow
depression appears in the reception level at its reception range
position according to the used frequency band. As a result, the
level varies according to the position of the terminal connected to
the power line 105, and the level difference between the best
reception level point and the worst reception level point attains
several dB to several tens of db. This is because of phasing of
used frequency and existence of standing wave. Phasing means
reception of transmission wave at the reception point passing
through a plurality of paths, mutual cancellation or enhancement by
the carrier wave phase, or reception signal fluctuation.
[0115] Next, an embodiment for reducing the influence of phasing or
the like will be described.
[0116] (1) The lamp equipment of the airport or the like has
specificity in the installation of the host station 108 and the
respective terminal 109. In short, the host station 108 is
installed at a position distal to the terminal 109, and respective
terminals 109 are installed so as to form a group.
[0117] Now, an equivalent circuit of a power line circuit
constituted of the power line 105 and the rubber transformer 110
can be represented as shown in FIG. 16, phasing or the like appear
as shown in FIG. 17A and FIG. 17B, as they are waves reflecting
from the central point of these equivalent circuits. When the host
station 108 transmit a signal to the terminal 109, it becomes a
transmission to a distal group as shown in FIG. 17A, and phasing
affect little the respective terminal 109. On the other hand, when
the terminal 109 transmits to the host station 108, it is affected
considerably by the phasing, as a stand alone remote host station
108 exists in one side as shown in FIG. 17B.
[0118] There, the system of the invention intends to lower the
attenuation slope of the reception level used for power-line
carrier, by installing compensation reactance elements L11, L12 in
the bypass filter apparatus 106 as shown in FIG. 18, and increasing
the lamp side impedance, and eventually to avoid the effect of the
phasing or the like and improve the transfer quality by increasing
the reception level.
[0119] (2) This monitoring control system, contrives compensation
means extending the distance between the power source side and the
lamp side similarly in the bypass filter apparatus 106, and signal
reception means by the host station 108.
[0120] To be more specific, as shown in FIG. 19, two compensation
reactance elements L11, L12 are connected in series between the
power source IN side line which is the one end connection end side
of an I type LC resonance circuit and the host station dedicated CT
composing the bypass filter apparatus 106, similarly, two
compensation reactance elements L21, L22 are connected in series to
the power source IN.multidot.COM side line which is the other one
end connection end side of the I type LC resonance circuit, and
further a compensation conductance element C11 is connected jumping
between respective elements L11-L12 and elements L21-L22, and by
installing a so-called H type distance prolongation compensation
circuit 132, the distance of IN-OUT (F side), IN/COM-OUT/COM (R
side) of the filter apparatus is increased apparently, to shift the
reception point, shift the bottom due to phasing, and receive at a
receivable level.
[0121] Further, the signal extraction section in the host station
108 extracts signal by a host station side CT serving as current
sensor; however, the signal attenuation increases under the
influence of the capacitance C between the power line-the earth,
because the distance from the respective terminal 109 is far.
[0122] There, a host station dedicated CT which is signal
extraction CT2, CT3 are installed at two points, power line primary
side IN-OUT line, and IN.multidot.COM-OUT.multidot.COM line, the
reception level of the one is lower and the reception level of the
other one is made receivable by the reception duplication, so as to
avoid the influence of reception level depression due to the
attenuation amount.
[0123] In addition, as bypass filter apparatus, as shown in FIG.
20, a capacitor FG may be provided at any one of #1 to #5 in a
circuit identical to FIG. 18.
[0124] FIG. 21 and FIG. 22 illustrate the reception duplication by
the host station.
[0125] The host station 8 synchronize with the zero cross of power
source waveform of the fixed current generator 104 based on a start
signal, detects the zero cross for every half cycle/cycle of power
source waveform from the start signal, and uses 1 to 4 cycle(s) as
command from the host station 108+space, while the response period
of respective terminal 109 to this command is allocated beforehand
for each of respective power source cycle. At this time, the
reception level from respective terminal 109 in the host station
108 is individually different.
[0126] There, the host station 108 receives a high level reception
signal extracted from a reception system of high reception level,
namely any of signal extraction CT2, CT3, through the reception
duplication processing shown in FIG. 22, by monitoring the rise
signal of respective terminal at all times. In short, the data
processing calculation control section 111 in the host station 108,
performs the diversity processing (S2) taking in power-line carrier
reception signals simultaneously from respective signal extraction
sections corresponding to a plurality of Ct, CT2, based on the
reception clock on by the zero cross detection of power source
waveform (S1), performs the reception processing including filter
processing of these taken in reception signals (S3, S3'), judges
respectively whether for instance 1.5 ms (90 degrees from the zero
cross of power source waveform) have passed or not (S4, S3'),
compares F side level and R side level by the comparator processing
of both reception signals when 1.5 ms have passed (S5, S6), takes
in the signal extracted by the signal extraction section of F side
signal if F side level is higher, and on the contrary takes in the
signal extracted by the signal extraction section of R side signal
if R side level is higher, and outputs the same (S7, S7').
[0127] On the other hand, in respective terminal 109 side,
compensation means as shown in FIG. 23 is installed.
[0128] In other words, in the terminal 109, the influence of
phasing is certainly low, some decrease of the reception level
still exists. Especially, according to the lamp construction state
of the power line 105, in the case where they are distant from the
adjacent lamp, the signal attenuated considerably under the
influence of the capacitance between the power line-the earth.
[0129] There, as the reception become impossible at the terminal
109 connected to a place of the power line 105 where the reception
level drops most, the reception level depression position is
shifted by additionally inserting one rubber transformer 110a to
the place, allowing to receive the reception signal at the
reception level of little depression in the concerned terminal
109.
[0130] Here, the secondary side of the added rubber transformer
110a is short-circuited, in the case when for instance a LC
resonance circuit 133 resonating the frequency used for power-line
carrier is connected, the reception level depression can be
eliminated by resonating with the used frequency by the LC.
[0131] FIG. 24 is a configuration diagram showing another
embodiment of the signal injection section in respective terminal
109.
[0132] The higher is the signal transmission level from respective
terminal 109, the higher is the communication quality. There, in
this configuration, a power source charge capacitor 137 is
installed at the output side of the power source circuit 136
constituted as a part of the power line modem 123b, power necessary
for the transmission is accumulated in the capacitor 137 per se
during signal non transmission period, and for example a FSK
modulated signal is transmitted consuming the accumulated power
during the transmission.
[0133] On the other hand, the respective terminal 109 is connected
to both extremities of the signal injection reactance 123d
respectively through FET138a, 138b as shown in FIG. 24, and so long
as the signal injection reactance 123d is connected in series with
the rubber transformer 110, power is consumed uselessly. Therefore,
useless power consumption can be avoided by short-circuiting the
both extremities of the signal injection reactance 123d for
instance by FET138a, 138b, during the non transmission period. 139
is a FET power source, 140 is control signal generation means for
controlling ON/OFF of FET 138a, 138b.
[0134] FIG. 25 illustrates the timing of FET 138a, 138b in the
signal injection section 123 of respective terminal 109.
[0135] Namely, the host station 108 detects the zero cross of power
source waveform, power-line carries command data to respective
terminal 109 using 1 to 3 cycle(s), thereafter, after having
installed a space of power source waveform 1 cycle, the answer
period of respective terminal to this host station command is
previously allocated for each respective power source cycle.
[0136] Here, in respect of the terminal 109-1, the positive side
FET 138a is short-circuited on this side of the answer area of its
own station, and the negative side FET 138b is short-circuited at
the time point past the zero cross. By doing so, the generation of
overvoltage at both extremities of the reactance can be prevented
beforehand, by connecting suddenly a signal injection reactance
123d when the signal is injected.
[0137] As mentioned above, the present invention allows to reduce
the influence of noise generated from the fixed current generator,
ensure a high quality transfer, even for a power-line carrier of
lower transfer quality, and further, realize the whole system at a
low cost by using the power-line carrier.
[0138] Additional advantages and modifications will readily occurs
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *