AU722707B2

AU722707B2 - Alarm reporting apparatus

Info

Publication number: AU722707B2
Application number: AU15139/97A
Authority: AU
Inventors: Kenichi Furukawa; Satoshi Matsumoto
Original assignee: Secom Co Ltd
Current assignee: Secom Co Ltd
Priority date: 1996-09-19
Filing date: 1997-03-07
Publication date: 2000-08-10
Anticipated expiration: 2017-03-07
Also published as: MY125066A; TW322565B; AU1513997A; JPH1097693A; CN1119775C; KR19980023992A; JP3544797B2; CN1177160A; KR100668991B1; SG54475A1

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Secom Co., Ltd.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Alarm reporting apparatus The following statement is a full description of this invention, including the best method of performing it known to me/us:la- BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an alarm reporting apparatus used for an alarm system utilizing a telephone line and, more particularly, to an alarm reporting apparatus capable of monitoring disconnection of a telephone line.

2. Description of the Related Art Various alarm systems for centrally monitoring buildings, condominiums, etc., by installing an alarm reporting apparatus in each building, connecting this 15 alarm reporting apparatus to a monitoring center at a remote place and monitoring the buildings at a monitoring center have been put into practical application. Various sensors such as burglar sensors, disaster sensors, etc., are connected to the alarm reporting apparatus in such an alarm system, and when any of these sensors detects abnormality, an alarm report is made to the monitoring center through the telephone line. When the telephone line is disconnected for some reason or other in this alarm system, the alarm report does not reach the monitoring center even the sensor detects abnormality, and the alarm system does not function.

Therefore, a signal is periodically transmitted from the alarm reporting apparatus to the monitoring center, at a time interval of one to two hours, for example, and the monitoring center monitors the periodical transmission of this signal. If this signal is not periodically received, the monitoring center judges that the telephone line is disconnected, and guards are sent to the corresponding building to confirm safety and to take necessary measures in accordance with the situation.

At the alarm reporting apparatus end, on the P\oper ssb j5 i39-97sp0.dc-f2/6/(O) -2other hand, a current flowing through the telephone line is monitored at the time of transmission of the periodical signal described above. If the current is not detected at this time, the alarm reporting apparatus judges that disconnection exists in the telephone line, and alerts stand-by personnel, by sounding a buzzer, that the telephone line is disconnected. Between the transmissions of the periodical signal, the telephone line is open and the detection of disconnection by the line current cannot be made. Therefore, a voltage between the lines is monitored while the line is open, and the telephone line is judged as being disconnected if the voltage is not detected.

However, detection of the line voltage is conducted by connecting a high resistance between the telephone lines to cause a very small current to flow and detecting this very small current. In other words, since the detection of disconnection by monitoring the line voltage is effected by detecting a smaller current in comparison with the monitor for the line current, it is easily susceptible to the influence of noise and is likely to invite an erroneous judgement. In contrast, since the monitor for disconnection using the line 15 current uses a greater current value and is less affected by noise, disconnection can be detected more reliably. It may be therefore conceivable to shorten the transmission interval of the periodical signal and to increase the number of times of monitoring by the line current. In this case, however, another problem develops in that the operating cost of the system increases because the number of times of transmission increases.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

SUMMARY OF THE INVENTION In an alarm reporting apparatus for reporting the occurrence of an abnormality to a destination through a telephone line, the present invention is directed to detecting disconnection of a telephone line at low cost without inviting an erroneous judgement, or at least to providing a useful alternative to known apparatus.

The present invention provides an alarm reporting apparatus for reporting the RAC occurrence of an abnormality to a predetermined destination through a telephone line upon detecting an abnormality, comprising: P\OPE R\SSB\5 I )7p.doC-.4)2/I -3line voltage monitor means for monitoring a line voltage of the telephone line, and detecting an abnormality of the line voltage; line current monitor means for monitoring a line current of the telephone line, and detecting an abnormality of the line current; line closing means for closing a D.C. circuit of said telephone line; and disconnection judgement means, operatively connected to said line voltage monitor means, said line current monitor means and said line closing means, the disconnection judgement means being arranged to cause said line closing means to close said D.C. circuit of said telephone line after said line voltage monitor means detects an abnormality, and to subsequently actuate said line current monitor means in order to judge if the line is disconnected based on whether the line current monitor means detects an abnormality in i the closed line and to output a disconnection signal if the line is judged to be disconnected.

•.In an alarm reporting apparatus for reporting the occurrence of an abnormality to a predetermined destination upon detecting such abnormality, the apparatus monitors a 15 voltage applied between the telephone lines when the telephone lines are open. When any abnormality is detected by the monitor using the line voltage, the telephone line is closed and a line current is monitored when any abnormality is detected during the monitoring of this line circuit, the apparatus judges that the telephone line is disconnected, and outputs a disconnection signal.

20 When the line voltage monitor means detects an abnormality, the disconnection judgement means causes the line closing means to close the D.C. circuit of the telephone line, and when the line current monitor means subsequently detects an abnormality when the line is closed, the judgement means judges that a disconnection has occurred in the telephone line, and outputs a disconnection signal. When no abnormal input is given by the line current monitor means while the line is closed, the judgement means judges that no disconnection exists in the telephone line.

According to this construction, when a disconnection occurs while the telephone line is open, the line voltage drops and the line voltage monitor means detects an P:\OPERSSB\ 15 t 39.97spe.dc-4)210(AAI -4abnormality. Next when the line current does not flow although the telephone line is closed, the line current monitor means detects an abnormality. In consequence, the disconnection judgement means outputs the disconnection signal. On the other hand, when the line voltage monitor means detects an abnormal voltage due to the noise although disconnection does not occur, the line current flows when the telephone line is subsequently closed, and the line current monitor means detects this line current. When this line current is detected, the disconnection judgement means judges that no disconnection has occurred. Therefore, the disconnection signal is not outputted, and an erroneous operation due to the noise can be prevented.

Monitoring by the line current is effected only when disconnection is judged as occurring by the monitor of the line voltage. Therefore, the number of times of closing of V. the line can be reduced, and an increase in the operation cost of the alarm system can be prevented.

In an embodiment of the present invention, it is also possible to accumulate the S 15 very small current in a capacitor and to monitor the discharge current of the capacitor instead of detecting the very small current due to the line voltage so as to monitor the line :voltage. In this case, the influences of the noise on the discharge current become smaller, so that the line voltage can be monitored under the state where the influences of the noise are small. Therefore, the occurrence of the erroneous operation due to the noise can be reduced, and the number of times of closing the line for monitoring the line current can be i further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The above features of the present invention will be more apparent from the following description, by way of example only, of the preferred embodiments with reference to the accompanying drawings, wherein: Fig. 1 shows a structural example of an alarm system P:\OPER\SSB\I151 39-97Spe.doc-42i6/W0 to which an alarm reporting apparatus of an embodiment of the present invention is applied; Fig. 2 is a circuit diagram showing an example of the alarm reporting apparatus of an embodiment of the present invention; Fig. 3 is a circuit diagram showing a line voltage monitor circuit used for the alarm, reporting apparatus shown in Fig. 2; Fig. 4 is a circuit diagram showing a line current monitor current used for the alarm reporting apparatus shown in Fig. 2; Fig. 5 is a flowchart showing a processing operation of a CPU shown in Fig. 2; and Fig. 6 is a circuit diagram showing a modified example of the line voltage monitor circuit shown in Fig. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be explained with reference to the accompanying drawings.

Fig. 1 is a block diagram showing the construction of an alarm system to which an o alarm reporting apparatus is applied.

In Fig. 1, reference numerals 3,3 denote buildings in which the alarm reporting :apparatus 4 is installed and which is the object of monitoring. The alarm reporting 20 apparatus 4 installed in each building 3 is connected to a central monitor 2 of a monitoring centre 3 at a remote place through a telephone line 5 and a switchboard 8. Reference S. numeral 10 denotes a stand-by station in which guards stand by. The stand-by station 10 is connected to the central monitor 2 of the central monitor center 1 through the telephone line 5 and the exchange 8.

Various sensors 6, 6, such as burglar alarms, disaster alarms, etc., disposed at predetermined positions of the building under supervision are connected to the alarm reporting apparatus 4. Further, telephones 7 and facsimiles 9 are connected to the 6 telephone line 5 through the alarm reporting apparatus 4.

When any sensor 6 outputs an alarm signal in the alarm system shown in Fig. 1, the alarm reporting apparatus 4 reports an alarm to the central monitor 2.

Upon receiving this alarm report, the central monitor 2 displays the occurrence of the alarm to the personnel inside the monitoring center 1. The monitoring center 1 reports the alarm to the stand-by station 10 in accordance with its kind and sends the guards to the building in which the alarm is detected.

The alarm reporting apparatus 4 transmits a predetermined signal to the central monitor 2 periodically (every hour, for example). The central monitor 2 monitors reception of this signal and when the periodical transmission is interrupted, it judges that disconnection occurs in the telephone line 5 and sends the guards to the building.

The guards sent to the monitor building confirm safety and take necessary measures in accordance with the given situation.

Fig. 2 shows the construction of the alarm reporting apparatus 4.

In the alarm reporting apparatus 4 of this embodiment, a disconnection judgement circuit 21 is inserted between the alarm monitor circuit 12 and the telephone line 5 so as to detect disconnection of the telephone line on the side of the alarm reporting apparatus 4. Various sensors 6, 6, and facsimiles 9 are connected to the alarm monitor circuit 12.

The alarm monitor circuit 12 normally connects the telephone line 5 to the telephones 7 and to the facsimiles 9. When any of the sensors 6, 6 detects abnormality and outputs the signal, the telephone line is closed by circuit closing means 13 and the alarm signal is sent to the central monitor 2. To detect the disconnection of the telephone line 5, the alarm monitor circuit 12 periodically closes the telephone line and 7 transmits a predetermined signal to the central monitor 2. Since the construction and the operation of this alarm monitor circuit 12 are well known in the art, its detailed explanation will be omitted.

The disconnection judgement circuit 21 is disposed so as to detect the disconnection of the telephone line on the side of the alarm reporting apparatus. Input terminals L1 and L2 of the disconnection judgement circuit 21 are connected to the telephone line 5 and its output terminals Li' and L2' are connected to the alarm monitor circuit 12. One of the input terminals L1 is connected to one of the output terminals LI' by the line current monitor circuit 24, and the other input •terminal L2 is directly connected to the other output 15 terminal L2'. A line voltage monitor circuit 23 is inserted between the input terminals L1 and L2. The output signal of the line current monitor circuit 24 and that of the line voltage monitor circuit 23 are inputted to a CPU (Central Processing Unit) 22.

An alarm circuit 25, comprised a buzzer or a flashing lamp, is connected to the CPU 22. The CPU 22 is connected to the line closing circuit 13 inside the alarm er monitor circuit 12, outputs a command signal for closing ~the line, and detects the line closing state.

Fig. 3 shows the construction of the line voltage monitor circuit 23.

The voltage between the input terminals L1 and L2 is rectified by a full wave rectifier D1 and is divided by resistors R1 and R2. The voltage of the power source V1 is divided by resistors R3 and R4. Both of these divided voltages are inputted to a comparator CPI, and a transistor Tr is ON/OFF controlled by the output of the comparator CPl. A photo-diode PDI of a photo-coupler PC1 is connected between the transistor Tr and the power source Vi. A photo-transistor PTl of the photocoupler PC1 is connected to the CPU 22.

Here, when the line voltage is a steady value, the 8 output of the comparator CPl becomes L (low) and the transistor Tr is turned OFF. Therefore, no current flows through the photo-diode PD1 and the photo-transistor PT1 is turned OFF. In contrast, when the line voltage drops, the output of the comparator CPl becomes H (high) and the transistor Tr is turned ON, so that the current flows through the photo-diode PD1 and the photo-transistor PT1 is turned ON.

Fig. 4 shows the construction of the line current monitor circuit 24.

A photo-diode PD2 of a photo-coupler PC2 is connected between the input terminal L1 and the output terminal LI'. The output of a photo-transistor PT2 is S" connected to the CPU 22. Here, when the current flows 15 through the telephone line 5, the photo-transistor PT2 is turned ON, and when the current does not flow, the photo-

S

transistor PT2 is turned OFF.

The operation of the CPU 22 of the disconnection judgement circuit 21 will be explained with reference to the flowchart of Fig. 5. By the way, this disconnection :..-.judgement circuit 21 is disposed for detecting the disconnection of the telephone line 5 on the side of the

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alarm reporting apparatus 3, as already described. The processing for detecting the disconnection of the telephone line 5 on the central monitor sensor side is executed by the alarm monitor circuit 12 in the same way as in the prior art systems.

First, whether or not the telephone line 5 is open is judged at the step S1 in Fig. 5. This judgement checks the state of the line closing circuit 13 inside the alarm monitor circuit 12. When the result proves NO (closed), the flow proceeds to the step S4 and when it is YES (open), the flow proceeds to the step S2.

The line voltage is monitored at the step S2. Here, the state of the photo-transistor PTl of the line voltage monitor circuit 23 is checked. Since the telephone line 5 is open under the state of the step S2, the state 9 can be judged as normal if the circuit voltage exceeds a predetermined value, and as abnormal if it is lower than the predetermined value. In other words, the state is judged as normal if the photo-transistor PT1 is turned OFF, and the flow returns to the step S1. If this transistor is turned ON, the state is judged as abnormal and the flow proceeds to the step S3.

There is the case where the state is judged as abnormal due to the influences of noise, although no disconnection exists in practice. Therefore, the flow proceeds to the operation for confirming the *disconnection of the step S3 et seq.

At the step 53, the CPU 22 outputs the signal to the line closing circuit 13 of the alarm monitor 15 circuit 12 and the telephone line is closed inside the alarm monitor circuit 12. Incidentally, when the line is closed, a predetermined signal is transmitted from the alarm reporting apparatus 3 to the monitoring center i, whenever necessary.

At the step S4, the line current is monitored.

Here, the state of the photo-transistor PT2 of the line current monitor circuit 24 is checked. Since the r telephone line 5 is closed under the state of the step S4, the state can be judged as normal if the line current exceeds a predetermined value and as abnormal if it is lower than the predetermined value. In other words, the state is judged as normal when the phototransistor PT2 is turned ON, and the flow returns to the step S1. If this transistor PT2 is turned OFF, the state is judged as abnormal and the flow proceeds to the step S5. Since monitoring of this line current is effected by using a greater current than the monitor of the line voltage, erroneous judgement caused by noise does not occur.

At the step S5, the reporting circuit 25 outputs the alarm, and the disconnection judgement operation is completed. As the alarm output, sounding the buzzer or 10 flashing the lamp is effected, and the alarm reporting apparatus side can determine the disconnection of the telephone line As explained above, when the possibility of the disconnection is judged as existing by monitoring the line voltage, the existence of the disconnection is subsequently judged by monitoring the line current.

Therefore, even when any erroneous judgement occurs during the monitor of the line voltage due to the noise, the disconnection of the telephone line can be always judged correctly. Since the monitoring of the line current is carried out only when the line is open and when an abnormality of the line voltage is detected, the number of times of closing the telephone line can be S 15 reduced, and an increase in the cost of the system operation can be prevented.

S"In the embodiment described above, the disconnection judgement circuit 21 is constituted separately from the alarm monitor circuit 12, but the disconnection judgement circuit 21 can be assembled into the alarm monitor :....circuit 12.

Next, a modified example of the line voltage monitor circuit 24 will be explained with reference to Fig. 6.

In Fig. 6, symbol C1 represents a capacitor for building up a very small current flowing due to the line voltage. A full wave rectifier D3 for rectifying the line voltage D3, a constant voltage circuit CCl, a phototransistor PT3 of a photo-coupler PC3 and a diode D4 are connected, as a charging circuit, to this capacitor Cl.

By the way, the constant voltage circuit CC comprises a transistor TRI, a zener diode ZDl and resistors R5, R6 and R7. Further, a discharge resistor R8, a phototransistor PT4 of a photo-coupler PC4 and a photodiode PD5 of a photo-coupler PC5 are connected, as a discharging circuit, to the capacitor Cl. The photodiode PD3 of the photo-coupler PC3 in the charging circuit and the photo-diode PD4 of the photo-coupler PC4 11 in the discharging circuit are alternately turned ON and OFF in a predetermined interval by a control signal from the CPU 22.

When the telephone line 5 is not disconnected and the line voltage is normal, the photo-diode PD3 in the charging circuit is turned ON and then the phototransistor PT3 is turned ON. During this ON period, the capacitor C1 is charged by the very small current due to the line voltage through the resistor R7. Next, when the photo-diode PD4 in the discharging circuit is turned ON, the photo-transistor PT4 is then turned ON, and the capacitor C1 is discharged through the discharge resistor R8. This discharge current turns ON the photodiode PD5 of the output photo-coupler PC5 and turns ON 15 the photo-transistor The CPU 22 judges that no disconnection exists in the telephone line 5 when a turn-ON of the phototransistor PT5 is detected at the time of discharging (when the photo-transistor PT4 is turned ON). When the telephone line 5 is disconnected, on the other hand, the line voltage does not exist any more. Therefore, even when the photo-diode PD3 in the charging circuit is turned ON, the capacitor C1 is not charged, so that the ~output photo-transistor PT5 is turned OFF during discharge. The CPU 22 judges that the possibility of the occurrence of disconnection exists in the telephone line 5 when it detects turn-OFF of the output phototransistor PT5 at the time of discharge. The flow proceeds to the processing of the step S3 et seq. in Fig. 5, and confirmation by the line current is made.

Even when the noise occurs, the influences of noise is smaller than that of the discharge current of the capacitor C1 building up the very small current.

Therefore, the possibility of the erroneous judgement of the line voltage due to the noise becomes smaller, and the number of times of closing the line for monitoring the line current can be further reduced.

12- When the condition of the telephone line becomes worse and noise frequently appears on the telephone line, the line closing operation might be conducted frequently.

In such a case, the frequency of the occurrence of the judgement of abnormality by the line voltage monitor circuit 26 and the subsequent judgement of normality by the line current monitor circuit 24 is monitored, and when the CPU 22 judges that the occurrence frequency is high, the CPU 22 executes the control so that the charging/discharging interval of the capacitor Cl of the line voltage monitor circuit 26 becomes longer. The occurrence frequency in this case is calculated by, for example, counting the number of times of the occurrence of such phenomena and when the counts exceeds five times within one hour, for example, the charging/discharging interval of the capacitor C1 is again set from 30 ms to 1 second.

:i According to the present invention, the :disconnection of the telephone line can be always monitored in the alarm reporting apparatus for reporting the occurrence of the alarm to the destination, and the "operation can be carried out at a low cost without eo inviting the erroneous judgement.

o o Throughout this specification and the claims which follow, unless the context .requires otherwise, the word "comprise", and variations such as "comprises" and

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"comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

1. An alarm reporting apparatus for reporting the occurrence of an abnormality to a predetermined destination through a telephone line upon detecting an abnormality, comprising: line voltage monitor means for monitoring a line voltage of the telephone line, and detecting an abnormality of the line voltage; line current monitor means for monitoring a line current of the telephone line, and detecting an abnormality of the line current; line closing means for closing a D.C. circuit of said telephone line; and disconnection judgement means, operatively connected to said line voltage monitor means, said line current monitor means and said line closing means, the disconnection judgement means being arranged to cause said line closing means to close said D.C. circuit of said telephone line after said line voltage monitor means detects an 15 abnormality, and to subsequently actuate said line current monitor means in order to judge if the line is disconnected based on whether the line current monitor means detects an abnormality in the closed line and to output a disconnection signal if the line is judged to be disconnected.

2. An alarm reporting apparatus according to claim 1, wherein said line voltage 20 monitor means includes: o a capacitor charged by a line current when said telephone line is open; means for repeatedly charging and discharging said capacitor in a predetermined cycle; and means for outputting an alarm signal when a discharge current is not detected at the time of discharge. PAOPfiRSSB\I 5 I39-97speAM41-2l)(f0 14

3. An alarm reporting apparatus substantially as hereinbefore described with reference to the drawings. DATED this 2 nd day of June 2000 Secom Co., Ltd. By its Patent Attorneys DAVIES COLLISON CAVE