CA1083242A - Monitor and alarm apparatus in loop line system - Google Patents
Monitor and alarm apparatus in loop line systemInfo
- Publication number
- CA1083242A CA1083242A CA259,928A CA259928A CA1083242A CA 1083242 A CA1083242 A CA 1083242A CA 259928 A CA259928 A CA 259928A CA 1083242 A CA1083242 A CA 1083242A
- Authority
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- Canada
- Prior art keywords
- disaster
- detectors
- data transmission
- digital signals
- groups
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Selective Calling Equipment (AREA)
Abstract
MONITOR AND ALARM APPARATUS
IN LOOP LINE SYSTEM
ABSTRACT OF THE DISCLOSURE
Monitor and alarm apparatus in a loop line system in which a plurality of detectors for generating analog signals representing the status of a disaster are distributed in an area to be monitored with respect to the disaster. The detectors are formed into a plurality of groups and each group of detectors is connected to a terminal control unit in which the analog signals from the group of detectors are converted into digital signals.
The terminal control units are connected in a loop line system and the digital signals from the terminal control units are sequentially collected to a central monitoring station which is also connected in the loop line system.
At the central monitoring station collected digital signals are compared with a predetermined monitor level to provide a display of the status of the disaster.
Since the present apparatus deals with analog signals representing the progress of the disaster, prediction of the disaster prior to the occurence of the disaster is achieved.
IN LOOP LINE SYSTEM
ABSTRACT OF THE DISCLOSURE
Monitor and alarm apparatus in a loop line system in which a plurality of detectors for generating analog signals representing the status of a disaster are distributed in an area to be monitored with respect to the disaster. The detectors are formed into a plurality of groups and each group of detectors is connected to a terminal control unit in which the analog signals from the group of detectors are converted into digital signals.
The terminal control units are connected in a loop line system and the digital signals from the terminal control units are sequentially collected to a central monitoring station which is also connected in the loop line system.
At the central monitoring station collected digital signals are compared with a predetermined monitor level to provide a display of the status of the disaster.
Since the present apparatus deals with analog signals representing the progress of the disaster, prediction of the disaster prior to the occurence of the disaster is achieved.
Description
~083'~
1 The present invention relates to a method and apparatus for monitoring an area for a disaster.
~ leretofore, since the prior art loop line system relating to disaster prevention handled only alarm contact outputs of the detectors arranged in the area to be monitored, it could detect an abnormal condition but could not determine actual status of the area to be monitored in analog fashion because the data transmitted were restricted to ON/OFF signals. Accord-ingly, the prior art loop line system has suffered asignificant limitation with respect to the function of the monitor and alarm apparatus.
The prior art system had also a significant i drawback in that it was not capable of predicting the -~
occurrence of the abnormal condition and monitoring status and variables derived from a plurality of data ., . ~
~'~ because it could not handle analog data representing-~ the status of the area to be monitored.
In order to resolve the above inconvenience, the present invention is characterized in that terminal control units are provided in the area to be monitored, and analog signals from deteotors) which are grouped with eaoh group comprising several detectors, are converted into ~; digital signals by multiplexers and analog-to-digital converters incorporated in the terminal control units , ~ .
~ and carried over the loop line.
`~ According to one aspect of the present invention ~l a method for monitoring and alarming a disaster in an : ' !
area, which comprises the steps of: generating a -~
` 30 plurality of analog signals by measuring the status ,., 1 :~k ' 't, ,, , ,:, . .' . ', ' .:" I '. , , ' ' 1083;~42 of the disaster at a plurality of detecting points distributed in the area to be monitored with respect to a disaster by means of detecting means at said detecting points; forming said plurality of analog signals into a plurality of groups each corresponding to a respective group of said detect-ing means, each group of said plurality of groups of analog signals includ-ing at least two kinds of signals indicative of two different parameters relating to said disaster; combining and converting each of said plurality of groups of analog signals into digital signals separately to form a series of digital signals for each of said groups at a plurality of terminal control units each connected to a corresponding one of said groups of detecting means; transmitting said series of digital slgnals from said plurality of terminalcontrol units to a data transmission control unit through a loop line sequentially in response to a request from said data transmission control unit, said loop line connecting said plurality of terminal control units and said data transmission control unit in a loop; transferring properly received digital signals at said data transmission control unit to a central monitor and alarm apparatus connected to the data transmission control units;
and comparing said transferred digital signals with a predetermined monitor level, and then generating an alarm signal at said central monitor and alarm apparatus.
According to another aspect of the present invention there is provided a monitor and alarm apparatus for a disaster comprising: a plurality of detectors disposed in an area to be monitored with respect to the disaster, said plurality of detectors being formed into groups and being adapted to generate an analog signal by measuring the status of the disaster, each group of said groups of detectors including at least two types of detectors which sense at least two different parameters relating to said disaster; a plurality of terminal control units each connected to a corres-ponding one of said groups of detectors, each of said plurality of terminal control units being operable to convert the analog signals of a respective group of detectors into a series of digital signals; a loop line for connect-` ing said plurality of terminal control units in a loop; a data transmission : ~ -2-,, .
control unit inserted in said loop line to form a loop line system, said data transmission control unit being adapted to receive said series of digital signals from said plurality of terminal control units and allow a properly received digital signal to be transferred therethrough; and a central ~, 5 ~; '~''; "''`.
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monitor and alarm apparatus connected to said data transmission control unit for comparing said transferred digital signals with a predetermined monitor level and for generating an alarm signal.
A preferred embodiment of the present invention is now described in conjunction with the accompanying drawings, in which:
Fig. 1 is a block diagram of one embodiment of the present monitor and alarm apparatus in the loop line system.
Fig. 2 is a detailed block diagram of N-th terminal control unit in Fig. 1 and detectors associated therewith.
In the preferred embodiment, since a micro-computer having a word length of 12 bits is used, an analog signal is converted into an 8-bit digital signal. For a proper function of the monitor and alarm apparatus, a digital signal of 8 to 12 bits may be appropriate.
Fig. 1 shows a block diagram of the preferred embodiment in which 11, 12 .... lN designate terminal control units respectively arranged in sectors or sub-areas in the area to be monitored, 111, 112, .... 115; 121;
122 .... 125; ....; and lNl, lN2 .... lN5 designate detectors located at ff detecting points and connected to the terminal control units, 2 designate ' a loop line, 3 a data transmission control unit, and 4 a central monitor and alarm apparatus, and where 41 designates a data processing unit, 42 an alarm data display unit, 43 a typewriting unit, 44 a memory unit .
.~ .
~f .`. ' _ _ .
:' .~ , ' -: - -:
1083Z4~
1 and 45 an input/output console. The data processing unit 41 used in the present embodiment performs data transmission processing function (data transmission check and collection) and data processing function in accordance with a program stored in the memory unit 44. The functions of the data processing unit 41 and the memory unit 44 may be performed by a usual micro-computer. ~nalog signals detected by the detectors 111, 112, ...... lN5 are periodically converted into 8-bit data signals in the terminal control units 11, 12, .... 1~. Whenever requested by the data transmission control unit 3 at a given time interval, the data from the five detectors associated with respective terminal ~
control units are each consolidated to a block of data, ~ -' which is then transferred to the data transmission control unit through the loop line, following an address signal for the terminal control unit. ~
~;~ The data transmission control unit compares ~ ~ -the received address signal with the transmitted address `~
signal, and if the comparison shows a coincidence it determines that a proper reception has been made and transfers the block of data transmitted following the -address signal to the central monitor and alarm apparatus as a detected signal for that address.
The data processing unit 41 decomposes the transferred block of data into 8-bit signals and simultaneously checks whether or not the data trans-mission has been properly made by information representing the characteristic of the data.
In the preferred embodiment, a double-transmission .
_ ~ _ . .
1 check system is used, in which data are normally read out twice for the same address and these data are compared with each other to determine whether they are correct data only when the comparison shows the coincidence.
If the data do not coincide with each other in the comparison, the data transmission control unit is instructed to read the same address again. This procedure is repeated up to three times, and if the readout of correct data is not attained within three repetitions, it is regarded that there is a failure in the data transmission control unit and the location of - the fault is displayed and printed out.
The faults in the data transmission may be -generally classified into the following two categories:
(1) Faults in the loop line
1 The present invention relates to a method and apparatus for monitoring an area for a disaster.
~ leretofore, since the prior art loop line system relating to disaster prevention handled only alarm contact outputs of the detectors arranged in the area to be monitored, it could detect an abnormal condition but could not determine actual status of the area to be monitored in analog fashion because the data transmitted were restricted to ON/OFF signals. Accord-ingly, the prior art loop line system has suffered asignificant limitation with respect to the function of the monitor and alarm apparatus.
The prior art system had also a significant i drawback in that it was not capable of predicting the -~
occurrence of the abnormal condition and monitoring status and variables derived from a plurality of data ., . ~
~'~ because it could not handle analog data representing-~ the status of the area to be monitored.
In order to resolve the above inconvenience, the present invention is characterized in that terminal control units are provided in the area to be monitored, and analog signals from deteotors) which are grouped with eaoh group comprising several detectors, are converted into ~; digital signals by multiplexers and analog-to-digital converters incorporated in the terminal control units , ~ .
~ and carried over the loop line.
`~ According to one aspect of the present invention ~l a method for monitoring and alarming a disaster in an : ' !
area, which comprises the steps of: generating a -~
` 30 plurality of analog signals by measuring the status ,., 1 :~k ' 't, ,, , ,:, . .' . ', ' .:" I '. , , ' ' 1083;~42 of the disaster at a plurality of detecting points distributed in the area to be monitored with respect to a disaster by means of detecting means at said detecting points; forming said plurality of analog signals into a plurality of groups each corresponding to a respective group of said detect-ing means, each group of said plurality of groups of analog signals includ-ing at least two kinds of signals indicative of two different parameters relating to said disaster; combining and converting each of said plurality of groups of analog signals into digital signals separately to form a series of digital signals for each of said groups at a plurality of terminal control units each connected to a corresponding one of said groups of detecting means; transmitting said series of digital slgnals from said plurality of terminalcontrol units to a data transmission control unit through a loop line sequentially in response to a request from said data transmission control unit, said loop line connecting said plurality of terminal control units and said data transmission control unit in a loop; transferring properly received digital signals at said data transmission control unit to a central monitor and alarm apparatus connected to the data transmission control units;
and comparing said transferred digital signals with a predetermined monitor level, and then generating an alarm signal at said central monitor and alarm apparatus.
According to another aspect of the present invention there is provided a monitor and alarm apparatus for a disaster comprising: a plurality of detectors disposed in an area to be monitored with respect to the disaster, said plurality of detectors being formed into groups and being adapted to generate an analog signal by measuring the status of the disaster, each group of said groups of detectors including at least two types of detectors which sense at least two different parameters relating to said disaster; a plurality of terminal control units each connected to a corres-ponding one of said groups of detectors, each of said plurality of terminal control units being operable to convert the analog signals of a respective group of detectors into a series of digital signals; a loop line for connect-` ing said plurality of terminal control units in a loop; a data transmission : ~ -2-,, .
control unit inserted in said loop line to form a loop line system, said data transmission control unit being adapted to receive said series of digital signals from said plurality of terminal control units and allow a properly received digital signal to be transferred therethrough; and a central ~, 5 ~; '~''; "''`.
7~
"~
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. .
~ .. : ,: .. . . .
ii " ., , , .
monitor and alarm apparatus connected to said data transmission control unit for comparing said transferred digital signals with a predetermined monitor level and for generating an alarm signal.
A preferred embodiment of the present invention is now described in conjunction with the accompanying drawings, in which:
Fig. 1 is a block diagram of one embodiment of the present monitor and alarm apparatus in the loop line system.
Fig. 2 is a detailed block diagram of N-th terminal control unit in Fig. 1 and detectors associated therewith.
In the preferred embodiment, since a micro-computer having a word length of 12 bits is used, an analog signal is converted into an 8-bit digital signal. For a proper function of the monitor and alarm apparatus, a digital signal of 8 to 12 bits may be appropriate.
Fig. 1 shows a block diagram of the preferred embodiment in which 11, 12 .... lN designate terminal control units respectively arranged in sectors or sub-areas in the area to be monitored, 111, 112, .... 115; 121;
122 .... 125; ....; and lNl, lN2 .... lN5 designate detectors located at ff detecting points and connected to the terminal control units, 2 designate ' a loop line, 3 a data transmission control unit, and 4 a central monitor and alarm apparatus, and where 41 designates a data processing unit, 42 an alarm data display unit, 43 a typewriting unit, 44 a memory unit .
.~ .
~f .`. ' _ _ .
:' .~ , ' -: - -:
1083Z4~
1 and 45 an input/output console. The data processing unit 41 used in the present embodiment performs data transmission processing function (data transmission check and collection) and data processing function in accordance with a program stored in the memory unit 44. The functions of the data processing unit 41 and the memory unit 44 may be performed by a usual micro-computer. ~nalog signals detected by the detectors 111, 112, ...... lN5 are periodically converted into 8-bit data signals in the terminal control units 11, 12, .... 1~. Whenever requested by the data transmission control unit 3 at a given time interval, the data from the five detectors associated with respective terminal ~
control units are each consolidated to a block of data, ~ -' which is then transferred to the data transmission control unit through the loop line, following an address signal for the terminal control unit. ~
~;~ The data transmission control unit compares ~ ~ -the received address signal with the transmitted address `~
signal, and if the comparison shows a coincidence it determines that a proper reception has been made and transfers the block of data transmitted following the -address signal to the central monitor and alarm apparatus as a detected signal for that address.
The data processing unit 41 decomposes the transferred block of data into 8-bit signals and simultaneously checks whether or not the data trans-mission has been properly made by information representing the characteristic of the data.
In the preferred embodiment, a double-transmission .
_ ~ _ . .
1 check system is used, in which data are normally read out twice for the same address and these data are compared with each other to determine whether they are correct data only when the comparison shows the coincidence.
If the data do not coincide with each other in the comparison, the data transmission control unit is instructed to read the same address again. This procedure is repeated up to three times, and if the readout of correct data is not attained within three repetitions, it is regarded that there is a failure in the data transmission control unit and the location of - the fault is displayed and printed out.
The faults in the data transmission may be -generally classified into the following two categories:
(1) Faults in the loop line
(2) Faults in the data transmission control unit and/or the data transmission terminal ~ control circuit.
;~ 20 For the former faults, a loop line switching circuit for detecting the fault in the loop line and switching the direction of transmission in the loop line ,;~ .
from clockwise to counterclockwise or vice versa is additionally provided to permit the use of the loop line in an essentially dual mode as a countermeasure i for the fault in the loop line.
For the latter faults, the double-transfer check system described above may be used.
~he data processing unit 41 performs three ~0 types of monitor (prediction, caution and alarm) for -- 5 ~
' ' "',`` ' ` ' :.-. .
, 1083Z~Z
1 the detected signals from the respective detectors by comparing the detected signals with a signal representative of a predetermined monitor level stored in the memory unit 44. In order to detect an abnormal condition at an early stage, the data processing unit 41 is provided with a special data processing function to derive a particular status variable (for example, an overall heat transfer coefficient, U = f(Tl, T2 .....
Tn)~ is obtained from temperatures T1, T2 ...... Tn detected by thermal sensors or thermocouples) from detected data or a changing rate of a particular variable (for example, a change rate of temperature ~ = dT) to enhance ~: :
the monitoring density in accordance with a program stored in the memory unit 44. :
: 15 When the abnormal condition is detected, it . is informed to an operator through the alarm data display ~ ~-: unit 42 and the typewriting unit 43, and the data at~ :
the time of the abnormal condition is maintained in the ::.
memory unit 44. When the system is constructed such that the operator verifies present value of the address from the input/output console 45, the detected data may be displayed in the alarm data display unit 42.
Fig. 2 shows a construction of the terminal ~ control unit lN, in which 5N designates a station for :
i 25 the loop line, 6N a data transmission terminal control .~ . circuit, 7N an 8-bit analog-to-digital converter circuit, ~N a multiplexer circuit for switching detected signals from the respective detectors, 9N a program control circuit, lONl, lON2 ...... lON5 measuring circuits for 30 the respective detectors, and lNl, lN2, ....... lN5 10832~Z
1 detectors associated with the terminal control unit.
~ ach of the detectors detects independently from others and includes its own adjuster to permit zero and span (range) adjustments for each detecting point.
The program control circuit 9N causes the multiplexer 8N to sequentially scan the analog signals from the respective detectors, the analog-to-digital converter 7N to convert them into 8-bit data signals t and the buffer memory to store them. When an address signal for addressing the terminal control unit lN is received from the central data transmission control unit over the loop line, the data transmission terminal control circuit 6N compare the received address signal with the preset address signal assigned to the terminal control unit lN, and if the comprison shows the coincidence the -,~ ~ data transmission terminal control circuit 6N instructs the interruption of the analog-to-digital conversion to the program control circuit in order to allow the trans- -!~ ~ 20 mission of a predetermined data to the central data transmission control unit, and the last five data which have been converted to digital form are transferred as a data block following to the address code assigned to the terminal control unit lN, to the central data ~ 25 transmission control unit via the loop line.
: In order to prevent an error from being introduced during the data transmission, the data signal transmitted to the central station includes a parity bit and a total bit in addition to start and ' 30 stop codes, which bits are used in error checking for 1 the data transmission.
The construction and the operation of the present apparatus have been fully discussed. An object of the present apparatus is to reduce the cost of wiring required in gathering the detected signals from a number of detectors distributed in the area to be monitored as well as to expand the capability of monitoring of the - detected data. The present apparatus can be applied to monitor and alarm apparatus in a tankyard, high pressure .
reaction facilities, a compressor and a plant, and it allows the assembling of the apparatus at a cheaper cost than required in the prior art apparatus.
The detector may be a temperature measuring element such as a thermocouple or a temperature sensitive resistor, a pressure transmitter by a ~ourdon's tube system or a strain gauge system, a flow rate and level '~ transmitter by a differential pressure system or a static capacitance type level transmitter, for the measurement of temperature, pressure, flow rate or i . .
~ 20 level. These different kinds of sensors may be . ~ ~
formed as a group of sensors which are connected to each of the terminal control units depending upon the event to be monitored.
1, :
; It should be understood that the data processing unit used with the present apparatus need not be provided ~ with the specific data processing function in order to i~ function as the monitor and alarm apparatus.
,: :
.
,'J
:,................... .
;~ 20 For the former faults, a loop line switching circuit for detecting the fault in the loop line and switching the direction of transmission in the loop line ,;~ .
from clockwise to counterclockwise or vice versa is additionally provided to permit the use of the loop line in an essentially dual mode as a countermeasure i for the fault in the loop line.
For the latter faults, the double-transfer check system described above may be used.
~he data processing unit 41 performs three ~0 types of monitor (prediction, caution and alarm) for -- 5 ~
' ' "',`` ' ` ' :.-. .
, 1083Z~Z
1 the detected signals from the respective detectors by comparing the detected signals with a signal representative of a predetermined monitor level stored in the memory unit 44. In order to detect an abnormal condition at an early stage, the data processing unit 41 is provided with a special data processing function to derive a particular status variable (for example, an overall heat transfer coefficient, U = f(Tl, T2 .....
Tn)~ is obtained from temperatures T1, T2 ...... Tn detected by thermal sensors or thermocouples) from detected data or a changing rate of a particular variable (for example, a change rate of temperature ~ = dT) to enhance ~: :
the monitoring density in accordance with a program stored in the memory unit 44. :
: 15 When the abnormal condition is detected, it . is informed to an operator through the alarm data display ~ ~-: unit 42 and the typewriting unit 43, and the data at~ :
the time of the abnormal condition is maintained in the ::.
memory unit 44. When the system is constructed such that the operator verifies present value of the address from the input/output console 45, the detected data may be displayed in the alarm data display unit 42.
Fig. 2 shows a construction of the terminal ~ control unit lN, in which 5N designates a station for :
i 25 the loop line, 6N a data transmission terminal control .~ . circuit, 7N an 8-bit analog-to-digital converter circuit, ~N a multiplexer circuit for switching detected signals from the respective detectors, 9N a program control circuit, lONl, lON2 ...... lON5 measuring circuits for 30 the respective detectors, and lNl, lN2, ....... lN5 10832~Z
1 detectors associated with the terminal control unit.
~ ach of the detectors detects independently from others and includes its own adjuster to permit zero and span (range) adjustments for each detecting point.
The program control circuit 9N causes the multiplexer 8N to sequentially scan the analog signals from the respective detectors, the analog-to-digital converter 7N to convert them into 8-bit data signals t and the buffer memory to store them. When an address signal for addressing the terminal control unit lN is received from the central data transmission control unit over the loop line, the data transmission terminal control circuit 6N compare the received address signal with the preset address signal assigned to the terminal control unit lN, and if the comprison shows the coincidence the -,~ ~ data transmission terminal control circuit 6N instructs the interruption of the analog-to-digital conversion to the program control circuit in order to allow the trans- -!~ ~ 20 mission of a predetermined data to the central data transmission control unit, and the last five data which have been converted to digital form are transferred as a data block following to the address code assigned to the terminal control unit lN, to the central data ~ 25 transmission control unit via the loop line.
: In order to prevent an error from being introduced during the data transmission, the data signal transmitted to the central station includes a parity bit and a total bit in addition to start and ' 30 stop codes, which bits are used in error checking for 1 the data transmission.
The construction and the operation of the present apparatus have been fully discussed. An object of the present apparatus is to reduce the cost of wiring required in gathering the detected signals from a number of detectors distributed in the area to be monitored as well as to expand the capability of monitoring of the - detected data. The present apparatus can be applied to monitor and alarm apparatus in a tankyard, high pressure .
reaction facilities, a compressor and a plant, and it allows the assembling of the apparatus at a cheaper cost than required in the prior art apparatus.
The detector may be a temperature measuring element such as a thermocouple or a temperature sensitive resistor, a pressure transmitter by a ~ourdon's tube system or a strain gauge system, a flow rate and level '~ transmitter by a differential pressure system or a static capacitance type level transmitter, for the measurement of temperature, pressure, flow rate or i . .
~ 20 level. These different kinds of sensors may be . ~ ~
formed as a group of sensors which are connected to each of the terminal control units depending upon the event to be monitored.
1, :
; It should be understood that the data processing unit used with the present apparatus need not be provided ~ with the specific data processing function in order to i~ function as the monitor and alarm apparatus.
,: :
.
,'J
:,................... .
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for monitoring and alarming a disaster in an area, which comprises the steps of: generating a plurality of analog signals by measur-ing the status of the disaster at a plurality of detecting points distributed in the area to be monitored with respect to a disaster by means of detecting means at said detecting points; forming said plurality of analog signals into a plurality of groups each corresponding to a respective group of said detecting means, each group of said plurality of groups of analog signals including at least two kinds of signals indicative of two different para-meters relating to said disaster; combining and converting each of said plurality of groups of analog signals into digital signals separately to form a series of digital signals for each of said groups at a plurality of terminal control units each connected to a corresponding one of said groups of detecting means; transmitting said series of digital signals from said plurality of terminal control units to a data transmission control unit through a loop line sequentially in response to a request from said data transmission control unit, said loop line connecting said plurality of terminal control units and said data transmission control unit in a loop;
transferring properly received digital signals at said data transmission control unit to a central monitor and alarm apparatus connected to the data transmission control units; and comparing said transferred digital signals with a predetermined monitor level, and then generating an alarm signal at said central monitor and alarm apparatus.
transferring properly received digital signals at said data transmission control unit to a central monitor and alarm apparatus connected to the data transmission control units; and comparing said transferred digital signals with a predetermined monitor level, and then generating an alarm signal at said central monitor and alarm apparatus.
2. The method according to claim 1, wherein in said combining and converting step, each of said plurality of groups of analog signals are sequentially scanned and converted into digital signals to produce a block of data representing information of said group of detecting means.
3. The method according to claim 1, wherein said comparing step further comprises a processing step of said digital signals to produce a signal representative of a particular status variable or a changing rate of a particular variable relating to the status of the disaster to be monitored.
4. The method according to claim 1, wherein a plurality of analog signals representing the status of the disaster include information obtained by measuring different types of phenomena of the disaster.
5. A monitor and alarm apparatus for a disaster, comprising: a plurality of detectors disposed in an area to be monitored with respect to the disaster, said plurality of detectors being formed into groups and being adapted to generate an analog signal by measuring the status of the disaster, each group of said groups of detectors including at least two types of detectors which sense at least two different parameters relating to said disaster; a plurality of terminal control units each connected to a corres-ponding one of said groups of detectors, each of said plurality of terminal control units being operable to convert the analog signals of a respective group of detectors into a series of digital signals; a loop line for connect-ing said plurality of terminal control units in a loop; a data transmission control unit inserted in said loop line to form a loop line system, said data transmission control unit being adapted to receive said series of digital signals from said plurality of terminal control units and allow a properly received digital signal to be transferred therethrough; and a central monitor and alarm apparatus connected to said data transmission control unit for comparing said transferred digital signals with a predeter-mined monitor level and for generating an alarm signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP104632/75 | 1975-08-28 | ||
| JP10463275A JPS5228298A (en) | 1975-08-28 | 1975-08-28 | Supervisory alarm unit by loop circuit system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083242A true CA1083242A (en) | 1980-08-05 |
Family
ID=14385810
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA259,928A Expired CA1083242A (en) | 1975-08-28 | 1976-08-26 | Monitor and alarm apparatus in loop line system |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5228298A (en) |
| CA (1) | CA1083242A (en) |
| MX (1) | MX3957E (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0614396B2 (en) * | 1982-02-22 | 1994-02-23 | 日本電気株式会社 | Security terminal |
| JPS61264835A (en) * | 1985-05-17 | 1986-11-22 | Kawamura Denki Sangyo Kk | Optical fiber data link system |
-
1975
- 1975-08-28 JP JP10463275A patent/JPS5228298A/en active Pending
-
1976
- 1976-08-26 CA CA259,928A patent/CA1083242A/en not_active Expired
- 1976-08-27 MX MX486476U patent/MX3957E/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| MX3957E (en) | 1981-10-15 |
| JPS5228298A (en) | 1977-03-03 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |