JP2775065B2 - Method and system for detecting short circuit of detector line in fire monitoring system using multiplex transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses a multiplex transmission and simplifies signal processing on a relay side for monitoring and controlling an addressed sensor in a fire monitoring system. The present invention relates to a short-circuit detection method for performing short-circuit protection and detection of a line and a fire monitoring system capable of implementing the method.

[Related Art] Recently, with the rise of buildings and the like, various fire monitoring systems have been developed and proposed which output quick and accurate warnings at the time of fire occurrence and provide prompt evacuation guidance. I have.

FIG. 9 shows the basic configuration of an intelligent fire monitoring system that has recently been in the spotlight among such fire monitoring systems.

Referring to the drawing, the fire receiver 100 and the repeater 200
Are connected via a multiplex signal line 1 and a sensor power supply line l2, a sensor line l3 is derived from each repeater 200, and a different address is assigned to the derived sensor line l3. Connected to a plurality of sensors SA.

Here, the sensor SA to which the address is assigned is composed of a smoke and heat sensor, and multiplexes the detected smoke information such as the smoke concentration and temperature in multiple stages together with the set address and an analog signal which is divided into multiple levels. It is configured to reply in the form of
A detector line l3 derived from each repeater 200 has a detector line l2 from a detector power supply 104 provided on the fire receiver 100 side.
Is configured to receive power supply via the.

In such a fire monitoring system, a fire receiver
CP according to the control program stored in the memory 106 of the 100
When a multiplexed signal with a repeater address is transmitted from the control means 102 composed of U to the multiplexed signal line 1 through the multiplexed transmission control unit 101 in a polling system, the multiplexed transmission control unit 202 of the repeater 200 having the same address is transmitted. Then, the control means 204 decodes the received multiplex signal to operate the multiplex transmission control section 203, and sends a sensor monitor signal to which a sensor address is added in the form of a multiplex signal to the sensor line l3. From the sensor SA that received the signal, a reply signal with the detected fire information added to the sensor address is returned in the form of a multiplex signal, and the control means 204 provided on the repeater 200 side decodes this reply signal, The alert from the sensor is discriminated, and when the alert from the sensor is confirmed, the multiplex transmission control unit 202 is operated again to send the signal to the fire receiver 1 side.

In this manner, the fire receiver 1 that has received the sensor alert is configured to operate the fire alarm means to generate a fire alarm.

However, in such a fire monitoring system, the multiplexed signal transmitted from the fire receiver 100 is converted into a completely different multiplexed signal inside the repeater 200 and transmitted to each of the sensors SA connected to the sensor line l3. Conversely, since the return signal from each sensor SA is converted into a different multiplexed signal inside the repeater 200 and returned to the fire receiver 1, the repeater 20
It is necessary to provide the advanced signal processing function to 0, and since the signal processing functions in the system are distributed for each repeater 200, the reliability of the system is also reduced.

Also, apart from such a problem, when the sensor line l3 is disconnected for some reason, the return signal from the sensor SA connected to the terminal side from the disconnection point stops,
It is not possible to distinguish between a disconnection of the sensor line 13 and a failure of the sensor SA, and this also reduces the reliability of the system.

[Problems to be Solved by the Invention] Therefore, the present inventor simplified the configuration and functions of the repeater, centralized the functions on the fire receiver side, reduced the total cost of the entire system, and improved the reliability. Although a fire monitoring method and a fire monitoring system in a fire monitoring system using multiplex transmission that can be used have been previously proposed, the present invention proposes a further improved invention of the proposed invention, and particularly, a short circuit protection of a sensor line and a short circuit protection. It is an object of the present invention to provide a method for performing short-circuit detection and an improved fire monitoring system capable of detecting disconnection of a sensor line in addition to such short-circuit protection and short-circuit detection.

[Means for Solving the Problems] The method of the present invention proposed to achieve the above object is as follows.
A fire receiver and a plurality of repeaters are connected by a multiplex signal line, and at least one of these repeaters is led to a sensor line to which a plurality of sensors assigned an address are connected. At the end of the line is connected a terminator that continuously performs a suction operation of the current supplied to the sensor line for a predetermined time when a voltage supply of a predetermined level or more is received. Power is supplied from the detector power supply of the fire receiver through the detector power line,
A transmission switch signal of a specific multiplex transmission level, which specifies a repeater address, is transmitted from the fire receiver side to the repeater side via a multiplex signal line by a polling method, and the repeater receiving the transmission switch signal On the side, following this transmission switching signal, the monitoring signal specified by the sensor address transmitted from the fire receiver side via the multiplex signal line is converted to a level corresponding to the sensor line, and the detection is performed as it is. While the signal is sent to the receiver line, the return signal returned from the address-attached sensor receiving the monitoring signal to the detector line is converted again to a specific multiplex transmission level at the repeater side and returned to the fire receiver side. In the fire monitoring system configured to perform the operation, when the voltage level of the detector line is lower than the alert level of the detector at the repeater, the voltage level of the detector line is increased. In addition to performing a protection operation for lowering the signal to a predetermined level, the reference voltage for discriminating the alarm of the sensor is reduced to a certain level, and the short-circuit detection signal thus generated on the repeater side is transmitted to the fire receiver. Side, and from the fire receiver that received this short-circuit detection signal,
A short-circuit recovery signal is output to release the protection operation on the repeater side, and thereafter, by repeating the same operation, a predetermined number of short-circuit detection signals set in advance on the fire receiver side are continuously output from the repeater side. When receiving the signal, the fire receiver outputs a short-circuit warning signal for the detector line.

The system of the present invention, which is proposed at the same time, connects a fire receiver and a plurality of repeaters with multiple signal lines,
These repeaters derive a sensor line to which at least a plurality of sensors assigned addresses are connected, and furthermore, when a voltage of a predetermined level or more is supplied to the end of these sensor lines, the sensing is performed. A terminator is connected to perform continuous suction of the current supplied to the detector line for a predetermined time, and power is supplied to the detector line from the detector power supply of the fire receiver through the detector power supply line. Then, a transmission switching signal of a specific multiplex transmission level designating a repeater address is transmitted from the fire receiver side to the repeater side via a multiplex signal line by a polling method, and the relay receiving the transmission switching signal is transmitted. On the detector side, following this transmission switching signal, the monitor signal designated by the detector address transmitted from the fire receiver side via the multiplex signal line is changed to a level corresponding to the detector line. Then, while sending it out to the detector line as it is, the return signal returned from the sensor with address which received the monitoring signal to the detector line is converted again to a specific multiplex transmission level by the repeater side, and the fire receiver In the fire monitoring system configured to perform a basic operation to return to the side, the fire receiver monitors a sensor line derived from a repeater in the system and a sensor connected to the sensor line, and at least, It is configured to output an alarm signal at the time of alarming of the sensor and at the time of determining the short-circuit of the sensing line. For this reason, it is connected to each repeater in the system via a multiplex signal line, and these repeaters are connected. A multiplex transmission control unit for transmitting a continuity test start signal to the multiplex signal line and monitoring a test discrimination signal returned from the repeater in order to monitor the sensor line; A control means for operating the multiplex transmission control unit in accordance with a specified control program, decoding the test discrimination signal received by the multiplex transmission control unit and performing necessary processing, and detecting each repeater in the system. At least a sensor power supply connected through a power supply line for supplying a power of a level necessary for the alarming operation of the sensor, wherein the relay is transmitted from the fire receiver via a multiplex signal line. A multiplex transmission control unit for receiving the conducted continuity test start signal and returning a test discrimination signal to the fire receiver, and setting an address to be added to the multiplex signal transmitted and received between the fire receiver. When the multiplex transmission control unit and the multiplex transmission control unit receive a monitor signal of a specific multiplex transmission level specified by the detector address from the fire receiver side, the monitor signal is sensed. While converting to the level according to the sensor line and sending it out,
A level conversion control section for causing the multiplex transmission control section to perform level conversion and send back a reply signal when receiving a reply signal from the sensor designated by the address connected to the sensor line; and a sensor on the fire receiver side. A sensor line supplied with power from the power supply through the sensor power line, and a voltage level generated in the sensor line, which is generated in the sensor line, decreases to a certain level lower than the alarm level of the sensor. A short-circuit detection and protection circuit for lowering the voltage level of the sensor line to a predetermined safety level; and, when the short-circuit detection and protection circuit is activated and a short-circuit recovery signal is received from the fire receiver, the sensor line is normally closed. A short-circuit recovery circuit that instantaneously opens the recovery contact of the mold and recovers the short-circuit operation of the sensor line;
When the multiplex signal control unit receives the continuity test start signal from the fire receiver, the voltage level supplied to the sensor line is reduced for a predetermined time by a non-operation of the terminator connected to the sensor line. Level, and after a lapse of a predetermined time, a continuity test means for returning the voltage supplied to the sensor line to a normal monitoring level, and a voltage level supplied to the sensor line by the continuity test means. Is lowered to a non-operation level of a terminator connected to the sensor line for a predetermined time, and is returned to a normal monitoring level after the lapse of the predetermined time. The basic operation of extracting the voltage levels occurring in the line and comparing the extracted voltage level with a predetermined reference level is performed. When a short circuit is detected, a level discriminator for forcibly lowering the reference level to a certain level and a test discrimination signal including a disconnection detection signal and a short circuit detection signal are sent back to the fire receiver. At least control means for judging the presence or absence of a short circuit in the sensor line based on the level judgment signal from the level judgment means and sending a test judgment signal to the multiplex transmission control unit is provided.

Further, according to the present invention described in claim 3, the short-circuit detection protection circuit outputs the short-circuit detection signal when the voltage level generated in the sensor line is reduced to a predetermined level lower than the time when the sensor is sounded. Then, a short-circuit detection circuit for lowering the reference level of the level determination means to a certain level, and a short-circuit holding circuit for operating the detection signal of the short-circuit detection circuit to lower the detector line to a certain safety level are combined. It is configured.

[Operation] In the method of the present invention, a continuity test signal is sent from the fire receiver side to the repeater side, and the repeater side receiving this continuity test signal reduces the voltage level supplied to the sensor line for a fixed time. The short circuit state of the sensor line can be detected in a simple manner.

When the continuity test is performed on the repeater side in this way and a short circuit is detected, a short circuit detection signal is sent to the fire receiver side in the form of a test discrimination signal. , The short-circuit signal is once released.

When such a short-circuit detection signal is continuously transmitted to the fire receiver and reaches a predetermined number, the fire receiver first determines a short-circuit and activates the alarm means.

Further, in the system of the present invention, when a short circuit occurs in the sensor line, a short circuit protection operation is performed irrespective of the fire receiver side, so that an accident due to the short circuit is also prevented.

Furthermore, according to the system of the present invention, as a basic control operation for monitoring the address-added sensor, the repeater simply performs level conversion on the multiplexed signal transmitted from the fire receiver to determine the occurrence of the alarm. However, for a general sensor, a change in the voltage level generated in the sensor line is monitored by the repeater to determine whether the alarm has occurred.

Further, in such a system of the present invention, the short-circuit detection of the detector line is performed by changing the voltage level supplied to the detector line by a fixed time by a continuity test means provided on the repeater separately from the fire receiver, The determination is made by monitoring the change in the voltage level generated in the sensor line by the level determination means.

Embodiment An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

(Configuration of Fire Monitoring System) FIG. 1 is a block diagram showing a fire monitoring system incorporating a main part configuration of the present invention, wherein a fire receiver 1 and each of the repeaters 2. A plurality of sensors SA, which are set with a sensor address, and an address are set on a sensor line l3 connected to the signal line 1 via a sensor power supply line l2 and derived from each of the repeaters 2. Are connected together, and a terminator 4 described later is connected to the end of the sensor line 13.

In such a system, each of the sensors SA and S connected to the detector power supply line l2 is connected to the detector power supply on the fire receiver 1 side.
Power is supplied from 14.

The fire receiver 1 generates a multiplex signal in accordance with the multiplex transmission control unit 11 and the control program stored in the memory 16, and processes the multiplex signal received by the multiplex transmission control unit 11 to generate a necessary control signal. A control means 12 constituted by a CPU for outputting, and an alarm means 13 for receiving an abnormal signal and generating an alarm when the disconnection of the sensor line 13 and the alarm of the sensors S and SA are determined in the control means 12. The I / O port 15 for outputting a control signal to a control terminal device (not shown) provided outside according to a control signal from the control means 12 and a sensor line l3 through a sensor power line l2. Detector SA
.., S... Are provided with a detector power supply 14.

One of the repeaters 2 is a multiplex transmission control unit 22 for transmitting and receiving a multiplex signal of a specific level to and from the fire receiver 1, and a multiplex signal received by the multiplex transmission control unit 22 is decoded to be preset. A control means 26 configured by a CPU for performing necessary control according to a control program; an address setting unit 21 for setting an address unique to the repeater for multiplex transmission processing; and a continuity test described later and a monitoring of a general sensor. Sensor power line l3
A level discriminator 28 that compares a voltage level occurring at a predetermined reference value with a predetermined reference value and outputs a discrimination signal to the control means 26, and a sensor line 13 for conducting a continuity test of the sensor line 13 as described later. The continuity test means 24 for supplying a voltage of a predetermined level in a simple procedure, and the voltage level of the sensor line l3 is monitored, and when the monitored voltage becomes a predetermined level lower than the level generated when the sensor issues an alarm, A short-circuit detection circuit 29a for outputting a short-circuit detection signal, and a short-circuit holding circuit for lowering the voltage of the sensor line l3 to a certain safety level when receiving the short-circuit detection signal from the detection circuit 29a, and multiplex transmission. The multiplex signal of a specific level received by the control unit 22 is converted and output to a signal level suitable for the sensor line l3, and a return signal from the sensor SA whose address is set can be accepted by the multiplex transmission control unit 22. Nare A level conversion control unit 23 having a configuration to be described later, and an insulated transmission circuit 25 that performs signal transmission between the multiplex transmission control unit 22 and the level conversion control unit 23 in a state separated from the power supply. And a transmission switching circuit 27 that receives supply of the sensor power supply 14 through the sensor power supply line l2 and permits or inhibits signal transmission between the multiplex transmission control unit 22 and the level conversion control unit 23 under the control of the control unit 26. It is provided with a configuration. Further, when receiving the short-circuit detection signal from the short-circuit detecting circuit 29a, the level determining means 28 changes the reference voltage of the level determining means to a constant level.

In the fire monitoring system having such a configuration, the repeater 2 receives a multiplex signal transmitted from the fire receiver 1 at a specific multiplex transmission level, and detects a disconnection of the sensor line l3.
Each control is performed, such as the alert monitoring of a sensor with an address and the alert monitoring of a general sensor without an address.

(Basic Operation of Fire Monitoring System) Next, each control operation in the fire monitoring system will be described.

(1) Alarm monitoring of a sensor with an address The fire receiver 1 multiplexes a transmission switching start signal of a specific level assigned a repeater address through a multiplex transmission control unit 11 according to a control program stored in a memory 16. When sequentially transmitted to the signal line 1 by the polling method, in each of the repeaters 2... Connected via the multiplexed signal line 1, the multiplexed transmission control unit 22 receives the multiplexed signal, and the control unit 26 controls the address setting unit. Check with the address set in 21.

As a result, in the repeater 2 whose addresses match, after a delay of a predetermined time TO (time sufficient for the CPU of the sensor side to be in the operating state), the gate is sent from the control means 26 to the transmission switching circuit 27. A signal is transmitted, and transmission / reception of a multiplex signal between the multiplex transmission control unit 22 and the level conversion control unit 23 via the insulated transmission circuit 25 is enabled to enter a multiplex signal transmission period. In this way, when the multiplex signal transmission period starts, the multiplex transmission control unit 22 receives the detector monitoring signal with the sensor address sequentially transmitted from the fire receiver 1 via the multiplex signal line 1. After that, the signal is transmitted to the level conversion control unit 23 through the transmission switching circuit 27 and the insulated transmission circuit 25.

In the level conversion control unit 23, after lowering the voltage level of the sensor line l3 from the normal monitoring level VCC to the VDD level, the amplitude is turned ON and OFF between VDD and V2 with the peak of VDD. A multiplex signal of a level adapted to the sensor line 13 is sent to the sensor line 13.

Thus, such a multiplex signal is transmitted to the level conversion control unit 23.
Is sent to the sensor line l3 through the sensor, a sensor return signal is returned from the addressed sensor SA.
This return signal is sent to the level conversion control unit via the sensor line l3.
When received at 23, the signal is sent to the multiplex transmission control unit 22 through the insulated transmission circuit 25 and the transmission switching circuit 27. The multiplex transmission control unit 22 converts the signal into a multiplex signal of a specific level again and sends it out to the multiplex signal line 1.

In such a fire monitoring system, the sensor return signal from the addressed sensor SA includes, in addition to the address assigned to the sensor SA, when the sensor SA is a smoke or heat sensor. , And an analog signal corresponding to the density and temperature level detected by the sensor. The analog signal is, for example, a signal obtained by classifying the smoke density into stages.

On the fire receiver 1 side, the control means 12 decodes the sensor return signals sequentially sent from the addressed sensors SA... When it is determined that the alarm has been issued, a fire detection signal is output to the alarm means 13 to notify a fire.

Thus, when communication with all the sensors SA connected to the sensor line 13 of the accessed repeater 2 is completed, the fire receiver 1 sends a transmission switching end signal of a specific level via the multiplex signal line 1 to the repeater. When the repeater 2 receives the transmission switching end signal, the control means 26 stops the operation of the transmission switching circuit 27 and ends the multiplex signal transmission period. As a result, the voltage of the sensor line 13 is Level is VCC again
Return to.

In this manner, between the fire receiver 1 and each of the repeaters 2, the transmission of the monitoring signal and the reception of the return signal are sequentially and repeatedly performed by the polling method, and each time the repeater 2 is accessed, an address is assigned. A signal corresponding to the level detected by the sensor (the above-described analog signal) is returned from the fired sensor to the fire receiver 1 (the above is the time in FIGS. 2A to 2C). See chart).

Further, as understood from the above description, during the monitoring period for such an addressed sensor SA, the repeater 2
On the side, the multiplex signal transmitted from the fire receiver 1 at a specific multiplex transmission level is converted into a level corresponding to the sensor line l3, and the return signal returned from each sensor SA is controlled by the control means in the repeater 2. In 26, the data is sent to the multiplex transmission control unit 22 without any decoding. That is, the repeater 2 performs only the level conversion of the signal transmitted and received between the multiplexed signal line 1 and the sensor line 13, and all the decoding of the return signal is performed on the receiver 1 side. Therefore, in such a fire monitoring system, not only the function of the repeater 2 can be simplified and the total cost of the system can be reduced, but also the central fire receiver side can collectively centralize the management.

(2) Alert Monitoring of General Sensor Next, a control operation of the general sensor during a monitoring period will be described.

The general sensor S to which no address is assigned normally opens the sensor line l3 and, when an alarm is issued, performs an operation of short-circuiting the sensor line l3 via a predetermined resistance component.
This side can detect this condition by monitoring the voltage level occurring in the sensor line 13 and determining that the level has dropped from the normal monitoring level to the alert level of the sensor.

When the fire receiver 1 transmits a monitoring start signal of a specific level specifying a repeater address via the multiplex signal line 1, the repeater 2 having the same repeater address enters a monitoring period of the general sensor.

During the monitoring period, the level discriminating unit 28 determines the voltage level of the sensor line 13 and the reference voltage set in the level discriminating unit 28 (a fixed level that is reduced by the operation of the voltage adjusting circuit 23 when the sensor S is informed. (Set to be slightly larger) to determine whether or not the general sensor S is alerted.

That is, when the voltage level of the sensor line 13 drops below the reference voltage level, the sensor S connected to the sensor line 13 is alerting, and when the detected voltage level exceeds the reference level, the alarm is issued. Judge that there is no information.

The control means 26 receives the determination signal from the level determination means 28,
The multiplexed signal is fetched through the insulated transmission circuit 25, and the fetched discrimination signal is sent to the multiplex transmission control unit 22 to be output to the multiplex signal line 1. It is decoded by the means 12 and the alarm of the sensor S is discriminated.
A fire detection signal is output by 13 and fire notification is performed.

When the monitoring of the general sensor S connected to the sensor line 13 is completed in this way, the fire receiver 1 transmits a monitoring end signal of a specific level to the repeater 2 via the multiplex signal line 1 and relays the signal. In response to the monitoring end signal,
The capturing of the discrimination signal by 26 is ended, and the monitoring period of the general sensor is ended.

The alert monitoring of the general sensor may be performed until the repeater receives the transmission start signal and enters a multiplex transmission period for monitoring the sensor. More easily.

(Configuration of Repeater) Next, the configurations of the repeater and the terminator used in the system of the present invention will be described in more detail.

FIG. 3 shows the repeater 2 used in the system of the present invention.
1 is shown in a block diagram, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

The repeater 2 is connected to a rectifier circuit 22a composed of a bridge diode for full-wave rectifying the multiplex signal transmitted from the fire receiver 1 side, and to the terminals NA and NB of the multiplex signal line 1,
A multiplex signal receiving circuit 22b for receiving a multiplex signal transmitted from the fire receiver 1 at a specific multiplex signal level;
Alternatively, the multiplex transmission control unit 22 includes a multiplex signal transmission circuit 22c that converts a multiplex signal transmitted through the level conversion control unit 23 into a multiplex signal of a specific level and transmits the multiplex signal to the fire receiver 1. The pulsating current component rectified by the rectifier circuit 22a is sent to the constant voltage power supply circuit 22A, and stabilized power is supplied from the constant voltage power supply circuit 22A to the control unit 26 side. .

Further, the level conversion control unit 23 includes a multiplex signal receiving circuit 22b.
Monitoring signal level conversion circuit 23a for converting the multiplexed signal transmitted from the
And a return signal level conversion circuit 23b for converting a return signal from the sensor SA with an address to a signal level to be sent to the multiplex signal conversion circuit 22c of the multiplex transmission control unit 22.

The level conversion control unit 23 and the multiplex transmission control unit 22 having such a configuration are connected in a state in which signal transmission is possible via the insulated transmission circuit 25 and the transmission switching circuit 27. The output side of the circuit 23a and the input side of the return signal level conversion circuit 23b are configured to be connected to a sensor line 13 via a terminal LN.

One continuity test means 24 is connected to terminals F,
The sensor power supply 14 is supplied from FG,
A voltage regulating circuit is configured by combining a current limiting circuit 24a that outputs an output voltage Vcc equal to the constant voltage power supply circuit 24b connected in parallel via the diode D1 and the current limiting circuit 24a. Adjustment circuit to sensor line l3
The output to is controlled or interrupted by controlling the switching circuit 24c.

The level determination unit 28 includes a short-circuit detection protection circuit described later.
It has a reference voltage 28b configured to lower the reference level when receiving a short-circuit detection signal from 29,
The voltage level generated at the terminal LN of No. 3 is
The discrimination signal is output by comparing and discriminating with the control signal, and the discrimination signal is input to the control means 26 via the insulated transmission circuit 25.

Here, the reference voltage 28b is equal to the value of the general sensor S except when a short circuit occurs.
Is generated, the voltage level generated in the detector line l3 (in this embodiment, the output level VEE of the constant voltage power supply circuit)
It is set slightly higher, so that the general detector S
Is issued, an "L" level determination signal is output.

On the other hand, the short-circuit detection protection circuit 29 monitors the voltage level of the detector line l3, and outputs a short-circuit detection signal when the monitored voltage becomes a predetermined level lower than the level generated when the detector issues an alarm. It comprises a circuit 29a and a short-circuit holding circuit 29b which, when receiving a short-circuit detection signal from the detection circuit 29a, lowers the voltage of the sensor line 13 to a certain safety level.

When a short-circuit recovery signal is received from the fire receiver 1, the 29A is activated to instantaneously open the normally closed recovery contact 29c provided on the sensor line l3, thereby immediately disconnecting the sensor line. Is a short circuit recovery circuit for returning to the state of FIG.

When a short circuit occurs in the sensor line l3, since the constant voltage power supply circuit 24b of the continuity test means 24 has low impedance, the power supply VEE is short-circuited by the short-circuited sensor line l3 and an excessive current flows. In order to prevent the constant voltage power supply circuit 24b from being damaged or from burning out at the place where the short circuit of the sensor line 13 occurs, the short circuit is detected by the short circuit detection circuit 29a and the short circuit is detected. The detection signal is output to the short-circuit holding circuit 29b and the detector circuit l3 is output.
Is forcibly reduced to a predetermined level, thereby maintaining the short-circuit detection operation of the short-circuit detection circuit 29a. Further, the reference voltage level of the level determination unit 28 is reduced to substantially zero volts by a short-circuit detection signal output from the short-circuit detection circuit 29a.

(Configuration of Terminator) Next, the configuration of the terminator will be described.

As shown in the circuit example of FIG. 4, the terminator 4 sets a reference voltage (about 4 volts) as a threshold, and when a higher voltage level is input to the input terminal IN, the output terminal OUT is turned off. It is configured to include a voltage detection circuit IC10 that is open and conversely short-circuits the output terminal OUT to the ground level when the input voltage is lower than the threshold.

To explain the configuration together with the operation, when at a normal monitoring level, a voltage of VCC (about 28 volts) is supplied to the sensor line l3, and this voltage is connected to a bridge diode.
Since the voltage is depolarized by BD and divided by resistors R10 and R11 and applied to the input terminal IN of the voltage detection circuit IC10, this voltage level exceeds the threshold value (about 4 volts), and therefore the output terminal OU
T is released, and the capacitor C is charged through the resistors R10, R12, R13 and the transistor Q10.

When the continuity test period starts in this state, the first time T (approximately
30 ms), the voltage level of the sensor line l3 is VDD
(Approximately 12 volts) (see FIG. 5 (a)), so that the divided voltage level by the resistors R10 and R11 of the terminator 4 becomes lower than the threshold value, and the output terminal OUT of the voltage detection circuit IC10 is grounded. Shorted to the level.

As a result, the electric charge charged in the capacitor C is output to the output terminal.
Discharged instantaneously (about 3 milliseconds) via OUT, diode D and resistor R13.

Next, the voltage of the sensor line l3 becomes the normal monitoring level VCC.
Then, the voltage level of the input terminal IN of the voltage detection circuit IC10 exceeds the threshold value, the output terminal OUT is opened, and the capacitor C is connected to the resistors R10, R12, R13 and the transistor Q.
Charged through 10.

Since the charging time T 'is longer than the discharging time (about 60 milliseconds), the transistors Q10 and Q11 are turned on during this time T', so that the detector line 13 is terminated by the resistor R14 and the sink current (about 30mA) (see Fig. 5 (b)),
The voltage level of the sensor line 13 becomes V1 (about 17 volts).

Then, when the transistors Q10 and Q11 turn off after the time T ', the level rises again to the same level as at the time of monitoring (see FIG. 5 (a)).

In other words, such a terminator 4 charges the capacitor when the voltage level of the sensor line l3 is higher than the predetermined operation level and flows the sink current. When the voltage level falls below the predetermined operation level, the terminator 4 instantaneously switches the capacitor. In the present embodiment, the suction current flowing at this time is set to be equal to the notification current at the time of notification of the general sensor.

The threshold of the operating voltage level of the terminator 4 may be set to 17 V or less in the case of the embodiment.

(Continuity Test Operation) Next, a control operation during the continuity test period will be described.

For this continuity test, it is necessary to connect the terminator 4 to the end of the sensor line l3. As described above, the terminator 4 has the voltage level of the sensor line l3 at the level during normal monitoring.
When the voltage is lowered from VCC to VDD below the non-operating level and then returned to the level VCC at the time of monitoring again, the sink current (general detector S generates an alarm) (For example, the same current level as in the case where the power is turned on).

In the method of the present invention, a continuity test is performed by using such a terminator 4.
Referring to the time chart of FIG. 6 and FIG. 6b, when the fire receiver 1 transmits a continuity test start signal with a repeater address via the multiplex signal line 1, the fire receiver 1 In the same way as the general sensor monitoring period, the repeater 2 whose repeater address matches matches enters the continuity test period.

Then, the control means 26 outputs a cutoff signal to the continuity test means 24 for a predetermined time T through the insulated transmission circuit 25 to cut off the supply of the sensor power to the sensor line 13. As a result, the voltage level supplied to the sensor line 13 through the current limiting circuit 24a is reduced from the normal monitoring level VCC to the voltage level VDD supplied through the monitoring signal level conversion circuit 23b. The voltage is returned to the VCC level again after the elapse of the time T.
(See FIG. 6 (a)).

For such a test operation, if there is no disconnection in the sensor line l3 and it is normal, the terminator 4 operates and the sink current flows through the sensor line l3 for a predetermined time T '. The voltage occurring on line l3 does not rise to VCC and remains at level V1. When the suction operation of the terminator 4 is completed, the voltage of the normal monitoring level is supplied to the sensor line 13 so that the voltage returns to VCC.

On the other hand, if the sensor line l3 is broken in the middle, the sink current by the terminator 4 disappears, so that after the time T, the sensor power of the normal monitoring level VCC is supplied again, The voltage level of the circuit line 13 immediately returns to VCC (see FIG. 6B).

That is, if the continuity test detection signals at both the first monitoring timing and the second monitoring timing are at the “L” level, the sensor line 13 is normal, and the continuity test detection signal is at the “L” level at the first monitoring timing. If the level is "H" at the second monitoring timing, it is determined that a disconnection has occurred in the sensor line l3.

The voltage level of this detector line l3 is
The control means 26 is monitored by the level determining section 28 having the reference voltage set to a voltage level between 1 and 1 after the time T1S (the first monitoring timing) and after the time T2S after outputting the cutoff signal. It is configured that the presence / absence of disconnection of the sensor line 13 is determined by taking in a later (second monitoring timing) determination signal.

Then, the control means 26 converts the discriminated continuity test detection signal into a corresponding multiplex signal and outputs it to the multiplex signal line 1 through the multiple transmission control unit 22. The fire receiver 1 multiplexes this multiplex signal into multiplex transmission control signals. It is received by the section 11 and decoded by the control means 12, but when such a disconnection detection signal is received for the first time, it is ignored, and then a similar continuity test signal is sent to the repeater 2 assigned the same address.

When such a disconnection detection signal is continuously transmitted from the same repeater 2 a preset number of times, it is determined that a disconnection has occurred in the sensor line for the first time, and the alarm means
13 is driven to output an alarm, and at the same time, the address of the repeater 2 in which the disconnection has occurred is displayed. And I / O as needed
A control signal is output to an external control terminal device via the port 15 to perform necessary disconnection alarm notification and the like.

In the continuity test, if a short circuit has occurred in the sensor line l3, the operation of the short-circuit detection protection circuit 29 lowers the sensor line l3 to a predetermined safety level, and at the same time, the level determination means 28 Since the reference voltage 28b of the second monitoring timing is reduced to almost zero level, the first and second monitoring timings
Since the output of the level determination circuit 28a in T1S and T2S is both "H", depending on the type of the determination signal obtained as a result of the continuity test, whether the sensor line 13 is normal, short-circuited, or It is possible to determine whether a disconnection has occurred.

FIG. 7 is a configuration diagram of an internal circuit showing a main part of the repeater.

This internal configuration diagram has a configuration excluding a multiplex transmission control unit, a control unit including a CPU, and an address setting unit.

The continuity test operation will be further described with reference to FIG.
When a continuity test start signal with a repeater address is input from the fire receiver 1, the repeater 2 having the same address decodes the signal with the CPU, sends out a cutoff signal, and outputs a photocoupler of the insulated transmission circuit 25. 25a for time T (about 30 ms)
Just turn on.

As a result, the transistor Q3 is turned on, the transistor Q4 is turned off, and the transistors Q5 and Q6 are turned off, so that the power supply V supplied to the terminal LN through the transistors Q5 and Q6 is turned on.
CC and power supply VEE are cut off, and terminal LN
1, level through transistors Q1, Q2 and diode D2
VDD (about 12 volts) is supplied.

Next, when the time T has elapsed, the CPU releases the cutoff signal, so that the photocoupler 25a is turned off. As a result, the transistors Q5 and Q6 are turned on, and the power supply VCC and the power supply VEE are supplied to the terminal LN again.

However, at this time, if there is no disconnection in the sensor line l3 and it is normal, a suction current (about 30 mA) flows through the terminator 4, so that the voltage of the terminal LN becomes V1 (about 17 volts), and the suction operation by the terminator 4 (Time T ': about 60 milliseconds), the voltage level of the terminal LN returns to the level of the power supply VCC again.

On the other hand, the level determination unit 28 of the repeater 2
The power supply VCC is divided by resistors R4 and R5, and has a reference voltage 28b of level ER (about 19 volts).

The comparator CMP2 monitors the voltage level of the terminal LN and transmits a test determination signal to the CPU through the photocoupler 25d.
(The first monitoring timing TS1) and the period from when the voltage is returned to the normal monitoring level until the termination current operation by the terminator 4 is completed (the second monitoring timing TS1).
In 2), the output level of the comparator CMP2 is monitored.

Therefore, when the sensor line 13 is normally connected, the comparator CM at the time of the first and second monitoring timings is set.
The output levels of P2 are all "L" levels.

However, if the voltage applied to the sensor line l3 is changed as described above, and if a disconnection occurs in the middle of the sensor line l3, the sink current by the terminator 4 will not flow. Immediately returns to the level of the power supply VCC after the elapse of the time T. Therefore,
The comparator CMP2 outputs an “L” level during the first monitoring, and outputs an “H” level during the second monitoring.

The CPU reads the test discrimination signals at the time of the first monitoring and the second monitoring to determine disconnection, and outputs a disconnection detection signal to the fire receiver 1 through the multiplex transmission control unit 22.

Further, the repeater 2 having such a configuration also has a protection function when a short circuit occurs in the sensor line l3. Next, the short circuit protection operation will be described.

When a short circuit occurs in the sensor line l3, since the constant voltage power supply circuit 24b of the continuity test means 24 has low impedance, the power supply VEE flows through the short-circuited sensor line l3, and the constant voltage power supply circuit 24b is damaged. Or a burnout may occur at the short circuit of the sensor line l3.

For this reason, the occurrence of a short circuit is detected by the short circuit detection circuit 29a, and the short circuit holding circuit 29b is operated to forcibly lower the voltage level of the sensor line 13 to a predetermined level, thereby detecting the short circuit of the short circuit detection circuit 29a. And the transistor Q9 is turned on to lower the reference voltage level of the comparator CMP2 to substantially zero volts.

A short circuit occurs in the sensor line l3, and the voltage level of the sensor line l3 is equal to or longer than a predetermined time determined by the capacitor C1 and the resistor R6 of the short-circuit detection circuit 29a. If the voltage drops below the level determined by the diode ZD2), the transistor Q7 is turned on to turn on the transistor Q8, thereby turning off the transistor Q4, opening the bases of the transistors Q5 and Q6, and A diode connected to the collector of transistor Q8, while blocking VCC and power supply VEE from being supplied to sensor line l3 through terminal LN.
The voltage level of the terminal LN is forcibly reduced to a predetermined level via D5 and the resistor R9, and the transistor Q7 is turned on by itself to perform a short-circuit protection operation.

In such a state, since the transistor Q9 is turned on by turning on the transistor Q7, the reference voltage 28b of the comparator CMP2 is reduced to substantially zero volt, and the output of the comparator CMP2 continues to be "H". "
Level.

As described above, when the short circuit occurs in the sensor line l3 and the short circuit protection operation is being performed, when the continuity test start signal is input from the fire receiver 1 to the repeater 2, the case of the disconnection detection is performed. Similarly, the transistors Q5 and Q6 are turned off by the cutoff signal from the CPU.However, since the transistors Q5 and Q6 are already turned off by short-circuit protection and the voltage of the terminal LN has dropped to a predetermined level, the comparator CMP2 is turned off. The output continues at "H" level.

Therefore, at the first monitoring time T1S, the output of the comparator CMP2 becomes “H” level, and even if the off operation of the transistors Q5 and Q6 by the CPU is canceled after the time T1 has elapsed,
Since the off state is continued by the short-circuit protection operation, the output of the comparator CMP2 is still at the “H” level.

The CPU detects the "H" level continuity monitoring signal at the time of the first monitoring and the second monitoring to detect a short circuit,
A short-circuit detection signal is output to the fire receiver 1 side.

On the other hand, on receiving the short-circuit detection signal, the fire receiver 1 transmits a recovery signal to the repeater 2, and the CPU drives a short-circuit recovery circuit (not shown) for a predetermined time to open the detector line. Open contact 29c and set relay contact 2
9d is closed to release the self-holding of the transistor Q7.

In this way, when the short-circuit protection is activated again after the relay is released and the sensor line 13 is connected, the short-circuit detection signal is transmitted again to the fire receiver 1 by the same operation as described above, When this operation is repeatedly performed a predetermined number of times, the fire detector 1 first detects the detector line.
It is determined that the short circuit of l3 has occurred, and is notified.

Therefore, even if a short circuit occurs in the sensor line l3, the short circuit protection is activated immediately to prevent the destruction of parts and the burnout of the sensor line l3, and the short circuit is repeated after confirming the short circuit on the fire receiver 1 side. Since the notification is performed, a malfunction does not occur, and the reliability of the system can be improved.

FIG. 8 is a time chart showing the operation of each unit when a short circuit occurs.

Finally, via the repeater 2, the fire receiver 1 and the sensor SA
The operation during the multiplex signal transmission period in which the multiplex signal is transmitted and received between the multiplex signal and the multiplex signal will be described.

Repeater 2 from fire receiver 1 via multiplex signal line 1
Then, when a transmission switching start signal with an address is input, the multiplexed signal is decoded by the CPU in the repeater 2 whose address matches, and the photocoupler 25a of the insulated transmission circuit 25 is driven. By driving the photocoupler 25a, the resistance from the power supply VDD
Since a current flows to the base of the transistor Q3 through R1, the transistor Q1, and the photocoupler 25a, the transistor
Q3 turns on and transistor Q4 turns off. Then, the base currents of the transistors Q5 and Q6 are cut off, and the power supply VCC supplied to the terminal LN connected to the sensor line l3 through the transistor Q5 and the power supply VEE similarly supplied to the terminal LN through the transistor Q6. Will be shut off. As a result,
The terminal LN is connected from the power supply VDD to the resistor R1, transistors Q1, Q2
And a level VDD (approximately 12 volts) is supplied through a diode D2 to enter a transmission period of a multiplex signal with the sensor SA.
Each addressed sensor connected to sensor line l3
SA indicates that the voltage level of the sensor line 13 has dropped (the power supply VCC
From the power supply to the power supply VDD) to drive the CPUs mounted on the respective devices to enter a multiplex signal reception state.

The time T1 (approximately
25 ms) (this time T1 is
The gate signal is output from the CPU to the transmission switching circuit 27, so that the photocoupler 25b of the insulated transmission circuit 25 is in a transmittable state and the multiplexing is performed. A multiplexed signal (a multiplexed signal having an amplitude of +24 volts and −24 volts) received by the multiplexed signal receiving circuit 22 b of the transmission control unit 22 is
The transistor Q1 is turned on and off according to the multiplex signal by being transmitted to the monitoring signal level conversion circuit 23a through b.

This multiplexed signal is a photocoupler 25 at +24 volts.
b is turned off and turned on at −24 volts, so that the transistor Q1 is turned off when the multiplexed signal is at +24 volts, and the power VDD supplied through the resistor R1 is changed to the Zener diode Z.
After being dropped to about 5 volts at D1, a voltage of about 5 volts is supplied to the sensor line 13 (terminal LN) through the transistor Q2 and the diode D2. Conversely, when the multiplex signal is at -24 volts, the transistor Q1 is turned on. Power supply VDD is a resistor R
1, Terminal LN through transistors Q1, Q2 and diode D2
Supply a voltage of about 12 volts. Therefore, the multiplexed signal having the amplitude of +24 or -24 volts is converted into a multiplexed signal having an amplitude of between 5 volts and 12 volts between the terminals LN and CN by the monitor signal level conversion circuit 23a. Transmitted to SA.

On the other hand, the address-attached sensor SA that has received the level-converted multiplex signal changes its internal impedance to change the current level flowing through the sensor line l3, and outputs a reply signal. The signal is detected by the return signal level conversion circuit 23c of the level conversion control unit 23.

That is, when one addressable sensor SA sends a reply signal, the current flowing through the sensor line 13 fluctuates, and the power supply VD
The current level supplied from D through the resistor R1, the transistors Q1, Q2, and the diode D2 fluctuates, and a voltage corresponding to the fluctuation of the current level is generated across the resistor R1.

This voltage is applied to the amplifier AMP1 of the return signal level conversion circuit 23b.
After conversion and amplification by the current / voltage conversion circuit composed of
By applying the power supply VDD to the comparator CMP1 having a reference voltage divided by the resistors R2 and R3, when the current of the detector line l3 increases, the comparator CMP1 outputs an "H" level voltage. Is decreased, the comparator CMP1 outputs an "L" level voltage.
Here, the time T1 from the start of the transmission period of the multiplex signal
When (about 25 milliseconds) elapse, the transmission switching circuit 27 is driven to the conductive state by the CPU as described above, and thereby the photocoupler 25b is set to the transmittable state.
At this time, the photocoupler 27a is simultaneously turned on, so that the output voltage of the comparator CMP1 is
25c, the multiplex signal transmission circuit 22c of the multiplex transmission control unit 22
Is transmitted to

That is, the sensor return signal from the addressable sensor SA is level-converted by the return signal level conversion circuit 23b and transmitted to the multiplex signal 1.

When the transmission and reception of the fire information by the multiplex signal between the fire receiver 1 and each of the sensors SA via the repeater 2 is completed, the fire receiver 1 sends a transmission switching end signal to the repeater 2. Then, the CPU of the repeater 2 determines the end of transmission / reception of the multiplex signal, switches the photocouplers 25a and 27a to the off state, and interrupts the signal transmission of the photocoupler 25b.

This turns off transistor Q3 and turns off transistor
Since Q4 is turned on, transistors Q5 and Q6 are turned on at the same time, power supply VCC and power supply VEE are supplied to terminal LN, and detector line l3 has the voltage level of power supply VCC and returns to the original monitoring state voltage level. I do.

Finally, the operation of the general sensor monitoring period in which the alarm signal of the general sensor S having no address is transmitted to the fire receiver 1 via the repeater 2 will be described.

Repeater 2 from fire receiver 1 via multiplex signal line 1
When a monitoring start signal with an address is input to the CPU, the multiplexed signal is decoded by the CPU through the multiplex transmission control unit 22, and the
Reads the output voltage level of the level discriminating unit 28 to determine the alarm status.

Here, when the general sensor S does not issue an alarm, the terminal LN connected to the sensor line l3 is at the voltage level of the power supply VCC. However, when the sensor S issues an alarm, the sensor line l3 switches to the sensor S3. Shorted through the internal resistance of the

However, due to the current limiting circuit 24a including the transistor Q5, the resistor R8 connected to the emitter thereof, and the diodes D6 and D7 connected to the base, the voltage drop of the resistor R8 causes the forward voltage of the diode D6 (or D7) to decrease. If it exceeds (approximately 0.6 volts), the current limit is applied and the output current of the transistor Q5 is limited. When the general sensor S issues an alarm, the output voltage level of the current limit circuit 24a falls below the level of the power supply VEE. As a result, the diode D1 conducts, and power is supplied to the detector line 13 from the power supply VEE having a low internal impedance.

On the other hand, the comparator CMP2 of the level determination circuit 28a has the reference voltage 28b of the level ER (about 19 volts) obtained by dividing the power supply VCC by the resistors R4 and R5. When the voltage level of the sensor line l3 is VCC, the alarm monitor signal of the "H" level is output. However, when the detector S issues an alarm, the voltage level of the sensor line l3 drops and becomes lower than the reference voltage ER. Therefore, an "L" level general sensor determination signal is output.

Therefore, the CPU determines the alert of the general sensor S based on the level of the general sensor determination signal, and outputs the signal to the fire receiver 1.
Side, a fire discrimination signal is transmitted, and the fire receiver 1 outputs a fire alarm according to the fire discrimination signal. This general sensor monitoring period is terminated when the repeater 2 returns a notification discrimination signal.

[Effects of the Invention] As can be understood from the above description, according to the method of the present invention, a monitoring signal with a detector address is transmitted and received between a fire receiver and a detector connected to a detector line. The repeater can be easily applied to a fire monitoring system using multiplex transmission, which simply converts the level of a multiplex signal transmitted and received between the two, and can easily protect and detect the short circuit of the sensor line. .

Further, according to the system of the present invention, it is possible to provide a fire monitoring system using a multiplex transmission system in which the function of a repeater is simplified and the total cost is reduced, and which is provided with a function of detecting a short circuit of a sensing line.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fire monitoring system according to the present invention.
FIG. 3 is a time chart showing signal transmission with an addressed sensor, FIG. 3 is a block diagram of an internal circuit of the repeater, FIG.
Fig. 5 is a circuit diagram of the terminator, Fig. 5 is a time chart for explaining its operation, Figs. 6a and 6b are explanatory diagrams of the principle of the continuity test method of the present invention, and Fig. 6a is when the sensor line is normal. Fig. 6b is an explanatory diagram of the operation at the time of disconnection, Fig. 7 is a circuit diagram of the main part inside the repeater, Fig. 8 is a time chart illustrating the operation at the time of short circuit, and Fig. 9 is a conventional fire. 1 shows a basic configuration diagram of a monitoring system. (Explanation of symbols) 1 ... Fire receiver 11 ... Multiplex transmission control unit 12 ... Control means 13 ... Alarm means 14 ... Sensor power supply 2 ... Repeater 21 ... Address setting unit 22 ... Multiplex transmission Control unit 23 Level conversion control unit 24 Continuity test means 24a Current limiting circuit 24b Constant voltage power supply circuit 24c Switching circuit 25 Insulated transmission circuit 26 Control means 27 Transmission switching circuit 28 Level detector 29 Short circuit protection circuit 29a Short circuit detection circuit 29b Short circuit holding circuit 29c Short circuit recovery contact 29A Short circuit recovery circuit 4 Terminator 1 Multiple signal line l2 ... Sensor power supply line l3 ... Sensor line Vcc ... Sensor monitoring level VDD ... Non-operating level T1S ... First monitoring timing T2S ... Second monitoring timing SA ... with address Detector S: General detector without address

Claims (3)

(57) [Claims] 1. A fire receiver and a plurality of repeaters are connected by a multiplex signal line, and at least a plurality of detectors to which addresses are assigned are connected to these repeaters. Further, a terminator is connected to the end of these sensor lines so that, when a voltage higher than a predetermined level is supplied, the current supplied to the sensor line is continuously absorbed for a predetermined time. Power is supplied to the detector line from the detector power supply of the fire receiver side through the detector power supply line, and from the fire receiver side to the repeater side,
A transmission switching signal of a specific multiplex transmission level in which a repeater address is specified is transmitted via a multiplex signal line by a polling method, and the relay receiving the transmission switching signal transmits the fire switching signal following the transmission switching signal. The monitor signal specified by the sensor address transmitted from the side through the multiplex signal line is converted into a level corresponding to the sensor line, and is sent to the sensor line as it is, while the address receiving the monitor signal is In a fire monitoring system configured to perform a basic operation of converting a return signal returned from the attached sensor to the sensor line to a specific multiplex transmission level again on the repeater side and returning it to the fire receiver side, When the voltage level of the sensor line falls below the alert level of the sensor on the repeater side, a protection operation that forcibly lowers the voltage level of the sensor line to a predetermined level. And the reference voltage for discriminating the alert of the sensor is reduced to a certain level, and the short-circuit detection signal thus generated on the repeater side is transmitted to the fire receiver side. The fire receiver side that has received the signal outputs a short-circuit recovery signal to release the protection operation on the repeater side, and thereafter, by repeating the same operation, the predetermined number of times set in advance on the fire receiver side Detector in a fire monitoring system using multiplex transmission characterized in that when a short-circuit detection signal is continuously received from a repeater, a short-circuit warning signal of a detector line is output at a fire receiver. Line short detection method. 2. A fire receiver and a plurality of repeaters are connected by a multiplex signal line, and at least a plurality of detectors to which addresses are assigned are connected to these repeaters. Further, a terminator is connected to the end of these sensor lines so that, when a voltage higher than a predetermined level is supplied, the current supplied to the sensor line is continuously absorbed for a predetermined time. Power is supplied to the detector line from the detector power supply of the fire receiver side through the detector power supply line, and from the fire receiver side to the repeater side,
A transmission switching signal of a specific multiplex transmission level in which a repeater address is specified is transmitted via a multiplex signal line by a polling method, and the relay receiving the transmission switching signal transmits the fire switching signal following the transmission switching signal. The monitor signal specified by the sensor address transmitted from the side through the multiplex signal line is converted into a level corresponding to the sensor line, and is sent to the sensor line as it is, while the address receiving the monitor signal is In a fire monitoring system configured to perform a basic operation of converting a return signal returned from the attached sensor to the sensor line to a specific multiplex transmission level again on the repeater side and returning it to the fire receiver side, The fire receiver monitors the sensor line derived from the repeater in the system and the sensor connected to the sensor line, and at least when the alarm of the sensor is issued and the short-circuit of the sensor line. It is configured to output an alarm signal at the time of fault detection. For this reason, it is connected to each repeater in the system via a multiplex signal line, and to monitor the sensor lines of these repeaters, A multiplex transmission control unit for transmitting a test start signal to the multiplex signal line and receiving a test determination signal including a short-circuit detection signal returned from the repeater; A control unit for operating the transmission control unit, decoding the test discrimination signal received by the multiplex transmission control unit and performing necessary processing, and connected to each repeater in the system via a sensor power line, At least a sensor power supply for supplying a power of a level necessary for the alarm operation of the sensor, wherein the relay is configured to transmit a signal transmitted from the fire receiver via a multiplex signal line. A multiplex transmission control unit for receiving a test start signal and returning the test discrimination signal to the fire receiver; and an address for setting an address to be added to the multiplex signal transmitted and received between the fire receiver. When the setting unit and the multiplex transmission control unit receive a monitor signal of a specific multiplex transmission level designated by the sensor address from the fire receiver side, the monitor signal is converted into a level corresponding to the sensor line. A level conversion control unit that, when sending out and receiving a reply signal from a sensor designated by an address connected to the sensor line, causes the multiplex transmission control unit to convert the level and sends back a reply signal; The sensor line supplied with power from the sensor power supply through the sensor power line and the voltage level generated in the sensor line, which is provided on this sensor line, are sensed. A short-circuit detection protection circuit for lowering the voltage level of the sensor line to a predetermined safety level when the signal level drops to a certain level lower than the alarm level of the detector; When a short-circuit recovery signal is received, the normally-closed recovery contact of the sensor line is instantaneously opened to recover the short-circuit operation of the sensor line. When a continuity test start signal is received, the voltage level supplied to the sensor line is reduced to a non-operation level of a terminator connected to the sensor line for a predetermined time, and after the predetermined time has elapsed. Is a continuity test means for returning the voltage supplied to the sensor line to a normal monitoring level, and the voltage level supplied to the sensor line by the continuity test means is The sensor line is connected to the sensor line in two periods, that is, when the terminator connected to the sensor line is lowered to the non-operation level for a predetermined time and when the level is returned to the normal monitoring level after the lapse of the period. Each of the generated voltage levels is extracted, and the extracted voltage level is compared with a predetermined reference level to perform a basic operation. On the other hand, when the short-circuit detection protection circuit detects a short circuit in the sensor line, the reference level is set to a certain level. Level discriminating means forcibly lowering the test signal to the fire receiver,
Utilizing multiplex transmission characterized by comprising at least control means for determining the presence or absence of a short circuit in a sensor line based on a level determination signal from the level determination means and sending a test determination signal to the multiplex transmission control unit. Fire monitoring system. 3. The short-circuit detection protection circuit outputs a short-circuit detection signal when a voltage level generated in a sensor line falls to a predetermined level lower than a time when an alarm is issued from the sensor. A short-circuit detection circuit that reduces the reference level of the sensor circuit to a certain level, and a short-circuit holding circuit that is activated by the detection signal of the short-circuit detection circuit to lower the sensor line to a certain safety level. The fire monitoring system using multiplex transmission according to claim 2.