JP7270351B2 - fire alarm system - Google Patents

Description

The present invention relates to a fire alarm system for notifying of fire.

Fire alarm systems are known that include a receiver and multiple sensors. In a fire alarm system, a receiver and a plurality of sensors are connected by transmission lines, and data is transmitted and received between the receiver and the plurality of sensors (see, for example, Patent Document 1). .

JP 2006-48211 A

If there is an anomaly in the transmission line between the receiver and the multiple sensors, data will not be transmitted or received normally between the receiver and the multiple sensors. As a result, there has been a problem that the receiver may not be able to report the occurrence of fire even though the detector has detected the fire.

Therefore, the present invention has been made in view of these points, and provides a fire alarm system capable of reducing the influence of an abnormality in a transmission line between a receiver and a plurality of sensors. With the goal.

The fire alarm system of the present invention comprises a sensor for detecting the occurrence of an abnormality in an installed area, and a receiver for receiving a sensor signal transmitted by the sensor, the sensor a sensor transmitter for transmitting a signal; and a sensor controller for causing the sensor transmitter to transmit the sensor signal, wherein the receiver connects between the sensor and the receiver. a current detection unit for detecting a transmission current flowing through a transmission line to which the a receiver control unit that determines that there is an abnormality in the transmission line when the transmission current detected by the current detection unit is less than a predetermined threshold.

The receiver further comprises a receiver transmitter for transmitting a receiver signal to the sensor, the sensor having a sensor receiver for receiving the receiver signal, and the receiver control The unit causes the receiver transmission unit to transmit the receiver signal including request information for requesting the sensor to transmit the sensor signal, and causes the receiver to transmit the receiver signal after transmitting the receiver signal. It may be determined that there is an abnormality in the transmission line based on the transmission current while the receiver is receiving the sensor signal.

The sensor further includes a current adjustment unit that adjusts the transmission current while transmitting the sensor signal, and the receiver control unit determines that there is an abnormality in the transmission line, the causing the receiver transmitter to transmit the receiver signal including a current increase request requesting the sensor to increase the transmission current or a current decrease request requesting the sensor to decrease the transmission current, and controlling the sensor; The unit transmits the sensor signal with the transmission current changed to the current adjusting unit when the sensor receiving unit receives the receiver signal including the current increase request or the current decrease request. You may let

The receiver control section causes the receiver transmission section to transmit the receiver signal indicating the magnitude of the transmission current detected by the current detection section, and the sensor control section controls the transmission current indicated by the receiver signal. The transmission current may be changed by the current adjustment unit based on the magnitude of the transmission current.

The fire alarm system comprises a plurality of sensors, and the receiver control section causes the receiver transmission section to transmit the receiver signal further including identification information for identifying each of the plurality of sensors. , the sensor further has a storage unit for storing its own identification information, and the sensor control unit stores the identification information included in the receiver signal received by the sensor receiving unit in the storage unit. The sensor transmitter may be caused to transmit the sensor signal on condition that it matches the stored identification information.

The receiver further has a display section for displaying an alarm indicating that there is an abnormality in the transmission line, and the receiver control section controls the identification signal included in the receiver signal transmitted by the receiver transmission section. the receiver signal transmitted by the receiver transmitter when it is determined that the transmission line is abnormal based on the transmission current while the sensor signal corresponding to the information is being received from the sensor; The alarm may be displayed on the display together with information specifying the sensor corresponding to the identification information included in the.

The receiver control unit outputs a first type alarm when the transmission current is less than a first threshold, and when the transmission current is greater than or equal to the first threshold and less than a second threshold larger than the first threshold A second type alarm may be output in certain cases, and it may be determined that the transmission current is normal when the transmission current is equal to or greater than the second threshold.

ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to reduce the influence by there being abnormality in the transmission line between a receiver and several sensors.

It is a figure which shows the outline|summary of the fire information system S. FIG. FIG. 4 is a diagram schematically showing transmission waveforms when the FSK transmission system is used; FIG. 4 is a diagram schematically showing voltages of signals received by a receiver; FIG. 3 is a diagram schematically showing voltages of signals received by a receiver; FIG. 10 is a diagram for explaining the effect when the sensor increases the transmission current; It is a figure which shows the structure of a receiver. 3 is a diagram showing an example of the internal configuration of a transmission circuit; FIG. FIG. 3 is a diagram showing an internal configuration example of a transmission current measuring circuit; It is a figure which shows the structure of a sensor. FIG. 5 is a diagram showing the relationship between the value of transmission current and the content of abnormality determination; It is a figure which shows an example of the electric current adjustment part which a sensor has. 4 is a flow chart of an operation in which a receiver control section executes processing for controlling transmission current; FIG. 4 is a flow chart of the operation of the sensor controller to adjust the transmission current; FIG.

[Outline of fire alarm system S]
FIG. 1 is a diagram showing an outline of a fire alarm system S. As shown in FIG. The fire alarm system S is a system that detects a fire and notifies that a fire has occurred. A fire alarm system S includes a receiver 1 and a plurality of sensors 2 (2A, 2B, 2C). A plurality of sensors 2 incorporate various sensors such as fire sensors and smoke sensors, and sense the occurrence of abnormalities in the installed area. The receiver 1 and each of the plurality of sensors 2 are connected via a transmission line T so that data can be transmitted and received. When the sensor 2 senses fire or smoke, it transmits a sensor signal indicating the occurrence of an abnormality to the receiver 1 via the transmission line T, and the receiver 1 receives the sensor signal transmitted by the sensor 2. receive. The receiver 1 and the sensor 2 transmit and receive data by, for example, the FSK (Frequency Shift Keying) transmission method.

FIG. 2 is a diagram schematically showing transmission waveforms when the FSK transmission system is used as an example of the transmission system. In the FSK transmission system, data 0 and data 1 are assigned sinusoidal signals having the same amplitude and different frequencies.

The transmission line T is generally made of a conductor whose main component is copper. A copper wire contains a resistance component (R), an inductance component (L), and a capacitance component (C), so that the transmitted signal is attenuated or the transmission waveform is distorted. The impedance (Z) increases as the distance between the receiver 1 and the sensor 2, that is, the transmission distance, increases, increasing the amount of signal attenuation.

3 and 4 are diagrams schematically showing voltages of signals received by the receiver 1. FIG. FIG. 3 shows waveforms of signals received by the receiver 1 when the distance between the receiver 1 and the sensor 2 is relatively small. FIG. 4 is a diagram showing waveforms of signals received by the receiver 1 when the distance between the receiver 1 and the sensor 2 is greater than that in FIG.

In FIG. 3, although the transmission wave height Vst and the reception wave height Vsr are slightly different, they show substantially the same values. Impedance Z is represented by Z=R+jωL+1/jωC. The received wave height Vsr is smaller than the transmitted wave height Vst due to the influence of R, L, and C described above. In FIG. 4, since the influence of R, L, and C of the transmission line T is increased, the difference between the transmitted wave height Vst and the received wave height Vsr is larger than in the case shown in FIG.

Address 1 to address n in FIGS. 3 and 4 are assigned to the plurality of sensors 2, respectively. The larger the number of the address, the greater the distance from the receiver 1 and the smaller the received wave height Vsr. there is Thus, the longer the transmission distance, the more the signal received by the receiver 1 is attenuated, and the probability that the data cannot be demodulated normally increases.

This phenomenon is caused not only by the transmission distance, but also by the fact that a wire that does not meet the design specifications of the receiver 1 and the sensor 2 is used as the transmission line T, or the transmission line T in the middle between the receiver 1 and the sensor 2 It also occurs due to a defective connection state of the transmission line T or an insulation failure caused by water adhering to the transmission line T. For example, when the sensor 2 is connected to the transmission line T, the connection may be in a semi-contact state due to an operation mistake. growing.

In the fire alarm system S of this embodiment, the receiver 1 detects failure of the transmission line T based on the magnitude of the signal received from the sensor 2 . Furthermore, when the receiver 1 detects a failure of the transmission line T, the receiver 1 instructs the sensor 2 connected via the transmission line T in which the failure has occurred to increase the current during transmission. . By operating the receiver 1 and the sensor 2 in this manner, the signal received by the receiver 1 from the sensor 2 can be appropriately demodulated regardless of the state of the transmission line T. FIG.

FIG. 5 is a diagram for explaining the effect when the sensor 2 increases the transmission current. FIG. 5(a) shows the state before the transmission current is increased, and the peak value of the sensor signal received by the receiver 1 is A1. FIG. 5(b) shows the state after the transmission current is increased, and the peak value of the sensor signal received by the receiver 1 is increased by ΔA from the peak value A1 in FIG. 5(a). is A2.
The configurations of the receiver 1 and the sensor 2 will be described in detail below.

[Configuration of Receiver 1]
FIG. 6 is a diagram showing the configuration of the receiver 1. As shown in FIG. The receiver 1 has a power supply circuit 11 , a user IF section 12 , a reception circuit 13 , a transmission circuit 14 , a transmission current measurement circuit 15 , a current/voltage conversion circuit 16 and a receiver control section 17 .

The power supply circuit 11 generates power for each circuit of the receiver 1 .
The user IF unit 12 includes a display unit (for example, a display) that displays an alarm indicating that a fire has occurred and an alarm indicating that there is an abnormality in the transmission line T, and a sound generation unit (for example, a speaker) that generates an alarm sound. , and a user interface such as an operation unit that receives user operations. The user IF unit 12 notifies the user of an alarm in a manner that allows the user to distinguish whether the alarm is a fire alarm indicating that a fire has occurred or a line failure alarm indicating that the transmission line T has an abnormality. The user IF unit 12 displays, for example, a fire alarm and a track fault alarm in different colors, or generates alarm sounds of different sounds.

The receiving circuit 13 is a circuit that functions as a receiver receiving section that receives a sensor signal from the sensor 2 . The receiving circuit 13 has an amplifying circuit for amplifying the signal received from the sensor 2 via the transmission line T, for example. The receiving circuit 13 may further include, for example, a differential amplifier circuit for impedance conversion, a bandpass filter, an impedance matching circuit, and the like.

The transmission circuit 14 is a circuit that functions as a receiver transmission section that transmits a receiver signal generated by the receiver control section 17 to the sensor 2 . FIG. 7 is a diagram showing an internal configuration example of the transmission circuit 14. As shown in FIG. The transmission circuit 14 has an impedance element 141 , a transistor 142 and an impedance element 143 . In FIG. 7, transistor 142 is illustrated as a bipolar transistor, but transistor 142 may be another type of transistor such as a field effect transistor.

Impedance element 141 and impedance element 143 are, for example, resistors, but may also include inductors or capacitors. The impedance element 141 functions as a protection resistor to prevent the transistor 142 from failing due to the flow of a current exceeding the rated current when the transistor 142 is saturated.

The base of the transistor 142 is connected to, for example, a D/A converter of the receiver controller 17 . The emitter of transistor 142 is grounded via impedance element 143 and the collector of transistor 142 is connected to current/voltage conversion circuit 16 via impedance element 141 . Transistor 142 changes the current flowing between the collector and the emitter based on the magnitude of the current input from receiver control section 17 . The collector-to-emitter current is the current that transistor 142 sinks from transmission line T. FIG.

If the voltage applied to the base of the transistor 142 by the receiver control unit 17 is Vb, the base-emitter voltage is Vbe, the intrinsic amplification factor of the transistor 142 is h, and the impedance value of the impedance element 143 is Z, the transmission current I is It is represented by the following formula.
I=h×(Vb−Vbe)/Z
Therefore, by varying the voltage applied to the base of the transistor 142 by the receiver control section 17, the transmission circuit 14 can generate the FSK signal.

The transmission current measuring circuit 15 functions as a detection section that detects the transmission current flowing through the transmission line T connecting between the receiver 1 and the sensor 2 . FIG. 8 is a diagram showing an internal configuration example of the transmission current measuring circuit 15. As shown in FIG. The transmission current measurement circuit 15 has an impedance element 151 and an amplifier 152 .

The impedance element 151 is an element having impedance provided between the receiver 1 and the current/voltage conversion circuit 16, such as a resistor. Impedance element 151 may comprise an inductor or a capacitor. Amplifier 152 amplifies the potential difference across impedance element 151 . The amplifier 152 inputs an analog signal corresponding to the amplified potential difference to the receiver control section 17 .

The current/voltage conversion circuit 16 is a circuit for generating a voltage on the transmission line T corresponding to the value of the current drawn by the transmission circuit 14, and serves as an electric element for generating a voltage corresponding to current fluctuations. , for example with resistance. When the current/voltage conversion circuit 16 has a resistance, the voltage of the transmission line T changes due to a voltage drop in the resistance corresponding to the value of the current drawn by the transmission circuit 14 . The current/voltage conversion circuit 16 generates, for example, a sinusoidal voltage corresponding to the sinusoidal current flowing from the transmission circuit 14 .

The receiver control section 17 is a circuit that controls each section of the receiver 1, and has, for example, a CPU (Central Processing Unit) and a storage section. The storage unit is, for example, ROM (Read Only Memory) and RAM (Random Access Memory). For example, when the receiver control unit 17 receives a detection signal indicating that a fire or smoke has been detected from the sensor 2 via the receiving circuit 13, the receiver control unit 17 causes the user IF unit 12 to display that a fire has occurred. , a speaker (not shown) to generate an alarm sound.

The receiver control unit 17 has an A/D conversion circuit, converts the analog signal input from the amplifier 152 into a digital value, and acquires the value of the potential difference between both ends of the impedance element 151 to obtain the transmission current. Determine the size of Further, the receiver control section 17 may determine whether or not the data is normally received by comparing the data transmitted from the sensor 2 with the expected value. Details of the operation of the receiver control unit 17 will be described later.

[Structure of sensor 2]
FIG. 9 is a diagram showing the configuration of the sensor 2. As shown in FIG. The sensor 2 has a power supply circuit 21 , a transmission circuit 22 , a reception circuit 23 , a sensor circuit 24 and a sensor control section 25 .

A power supply circuit 21 generates power for each circuit of the sensor 2 .
The transmission circuit 22 is a circuit for transmitting the sensor signal generated by the sensor control section 25 to the receiver 1 . The transmission circuit 22 has an internal configuration equivalent to that of the transmission circuit 14 of the receiver 1, for example. When receiving a request to transmit a sensor signal from the receiver 1 in a line confirmation mode, which is a mode for confirming the state of the transmission line T, the transmission circuit 22 transmits a sensor signal for line confirmation. Transmitter circuit 22, when transmitting a sensor signal for line verification, uses a sensor signal that can be transmitted on transmission line T to allow transmission current to be verified in a state that is most susceptible to the specific impedance of transmission line T. It is preferable to transmit the signal that toggles the current amplitude most frequently (ie, the signal with the highest frequency) of the instrument signals.

The receiving circuit 23 is a circuit for receiving the signal transmitted by the receiver 1 . The receiving circuit 23 has an internal configuration equivalent to that of the receiving circuit 13 of the receiver 1, for example. The receiving circuit 23 inputs the received receiver signal to the sensor control section 25 .

Sensor circuit 24 is a circuit that includes sensors for sensing abnormal conditions such as fire or smoke. The sensor circuit 24 inputs a sensing signal output by the sensor to the sensor control section 25 .

The sensor control section 25 is a circuit that controls each section of the sensor 2, and has, for example, a CPU and a storage section. For example, the sensor control unit 25 controls the transmission circuit 22 to transmit a sensor signal to the receiver 1 based on the abnormality detection signal input from the sensor circuit 24, or controls the control signal received from the receiver 1. The sensor circuit 24 is controlled based on.

The storage unit is, for example, ROM and RAM, and stores a sensor ID (eg, address) that is identification information of the sensor 2 itself. The sensor control unit 25 transmits the sensor signal to the transmission circuit 22 on condition that the sensor ID included in the receiver signal received by the reception circuit 23 matches the sensor ID stored in the storage unit. to be sent. By operating the sensor control unit 25 in this way, even when a plurality of sensors 2 are connected to the same transmission line T, the plurality of sensors 2 are prevented from transmitting sensor signals at the same time. can be

[Method for Determining Abnormality of Transmission Line T]
A method by which the receiver control unit 17 determines that an abnormality has occurred in the transmission line T will be described in detail below.
The receiver control unit 17 determines that there is an abnormality in the transmission line T when the transmission current detected by the transmission current measuring circuit 15 while the receiving circuit 13 is receiving the sensor signal is less than a predetermined threshold. do. The predetermined threshold value is, for example, the value of the transmission current when the probability that the receiving circuit 13 cannot receive the sensor signal normally exceeds the allowable range. When the receiver control unit 17 determines that the transmission line T has an abnormality, the receiver control unit 17 causes the user IF unit 12 to display that the transmission line T has an abnormality, or causes the speaker to generate an alarm sound.

The receiver 1 may determine that there is an abnormality in the transmission line T when set to a line confirmation mode for confirming the presence or absence of an abnormality in the transmission line T. In the track confirmation mode, the receiver control unit 17 caused the transmission circuit 14 to transmit a receiver signal including request information for requesting the sensor 2 to transmit the sensor signal, and caused the receiver signal to be transmitted. It may be determined later that there is an abnormality in the transmission line T based on the transmission current while the receiving circuit 13 is receiving the sensor signal.

Since the receiver control unit 17 has such a configuration, the receiver control unit 17 can receive the sensor signal after transmitting the receiver signal including the request information instead of constantly monitoring the transmission current. Since it is sufficient to monitor the transmission current while there is a possibility, the processing of the receiver control section 17 is reduced. The transition to the track confirmation mode may be performed by the operation of the administrator of the fire alarm system S, or the receiver 1 may periodically execute the track confirmation mode.

When a plurality of sensors 2 are provided in the fire alarm system S, the receiver control unit 17 controls the receiver including identification information (hereinafter referred to as a sensor ID) for identifying each of the plurality of sensors 2. The signal may be transmitted by transmission circuit 14 . By including the sensor ID in the receiver signal, the receiver control section 17 can transmit individual request information to the sensor 2 .

The receiver control unit 17 can use the sensor IDs to sequentially confirm whether or not there is an abnormality in the transmission line T between each of the plurality of sensors 2 . Specifically, the receiver control unit 17 sequentially sends a receiver signal including a sensor ID and request information requesting transmission of the sensor signal to the transmission circuit 14 while changing the sensor ID. send. For example, the receiver control unit 17 causes the transmission circuit 14 to transmit one receiver signal, waits until a sensor signal responding to the receiver signal is received, and then transmits the next sensor signal including a different sensor ID. The receiver signal is transmitted to the transmitter circuit 14 .

The receiver control unit 17 detects an abnormality in the transmission line T based on the transmission current while receiving the sensor signal from the sensor corresponding to the sensor ID included in the receiver signal transmitted by the transmission circuit 14. Determine whether or not there is If the receiver control unit 17 determines that there is an abnormality in the transmission line T, the receiver control unit 17 sends an alarm to the user IF together with information specifying the sensor corresponding to the sensor ID included in the receiver signal transmitted by the transmission circuit 14. It is displayed on the display unit of the unit 12 . For example, the user IF unit 12 has a light emitting diode corresponding to each of the plurality of sensors 2, and when the receiver control unit 17 determines that an abnormality has occurred in one transmission line T, an abnormality has occurred. The light-emitting diode corresponding to the sensor 2 connected via the transmission line T judged to have been turned on is turned on.

The receiver control section 17 may control the user IF section 12 so as to output different determination contents depending on the value of the transmission current. FIG. 10 is a diagram showing the relationship between the value of transmission current and the content of abnormality determination.

For example, the receiver control unit 17 controls the user IF unit 12 to output a first type alarm when the transmission current is less than the first threshold (for example, less than α1 in FIG. 10). The receiver control unit 17 instructs the user to output a second type alarm when the transmission current is equal to or greater than the first threshold and less than a second threshold that is greater than the first threshold (for example, α1 or more and less than α3 in FIG. 10). It controls the IF unit 12 . The receiver control unit 17 determines that the transmission current is normal when the transmission current is equal to or higher than the second threshold (α3 or higher in FIG. 10), and controls the user IF unit 12 so as not to output an alarm. The receiver control unit 17 may output an alarm when the transmission current is equal to or greater than a third threshold (α4 or greater in FIG. 10) that is greater than the second threshold and the transmission current is excessive.

The first type of alarm is an alarm that is output when the sensor 2 is out of order, the sensor 2 is not connected to the transmission line T, or the like. The second type of alarm is an alarm that is issued when it is estimated that the transmission line T is abnormal while the sensor 2 is estimated to be normal.

The receiver control section 17 may control the user IF section 12 to output a plurality of types of second type alarms based on whether or not the receiver signal is normally received. For example, when the data error rate after demodulating the sensor signal is less than the allowable range (for example, α1 or more and less than α2 in FIG. 10), the receiver control unit 17 outputs an alarm recommending improvement. The user IF unit 12 is controlled as follows. If the data error rate after demodulating the sensor signal is above the allowable range (for example, α2 or more and less than α3 in FIG. 10), the receiver control unit 17 outputs an alarm prompting confirmation of the transmission line T. The user IF unit 12 is controlled so that In this manner, the receiver control unit 17 controls the user IF unit 12 so as to output different types of alarms based on the transmission current and the data error rate, so that the user can accurately determine the state of the transmission line T. be able to understand and take appropriate action.

[Transmission current adjustment]
The fire alarm system S may operate to change the transmission current when it is determined that the transmission line T has an abnormality. The fire alarm system S operates, for example, to increase the transmission current when the transmission current is too small, and to decrease the transmission current when the transmission current is too large. Specifically, when the receiver control unit 17 determines that there is an abnormality in the transmission line T based on the transmission current, a current increase request requesting the sensor 2 to increase the transmission current or decrease the transmission current cause the transmitter circuit 14 to transmit a receiver signal containing a current reduction request requesting that the transmitter circuit 14 The sensor 2 has a current regulator that regulates the transmission current while transmitting the sensor signal, and the sensor controller 25 causes the receiver circuit 23 to receive the receiver signal containing the current increase request. If so, cause the current adjustment unit to transmit the sensor signal with the transmission current changed (increased or decreased).

FIG. 11 is a diagram showing an example of a current adjusting section included in the sensor 2. As shown in FIG. FIG. 11 shows the transmitter circuit 22, the receiver circuit 23, the sensor controller 25 and the current regulator 27. FIG. The current adjusting section 27 has a current limiting circuit 26 and a switch 251 .

The transmission circuit 22 has an impedance element 221, a transistor 222 and an impedance element 223, like the transmission circuit 14 shown in FIG. The sensor control section 25 has a switch 251 that forms the current regulation section 27 together with the current limiting circuit 26 . Current limiting circuit 26 is connected to the emitter of transistor 222 along with impedance element 223 . The current limiting circuit 26 switches between a state of being connected in parallel with the impedance element 223 between the emitter of the transistor 222 and the ground and an open state based on the state of the switch 251 of the sensor control section 25. .

When switch 251 is short-circuited, impedance element 223 and current limiting circuit 26 are connected in parallel between the emitter of transistor 222 and the ground. When the switch 251 is not short-circuited, the impedance element 223 is provided between the emitter of the transistor 222 and the ground, and the current limiting circuit 26 is not provided. As a result, when the switch 251 is short-circuited, the impedance between the transmission line T and the ground becomes smaller than when the switch 251 is not short-circuited, the current drawn by the transistor 222 increases, and the transmission current increases. do.

Instead of causing the transmission circuit 14 to transmit a receiver signal including a current increase request for increasing the transmission current or a current decrease request for decreasing the transmission current, the receiver control unit 17 causes the transmission current measurement circuit 15 to detect The transmitter circuit 14 may be caused to transmit a receiver signal indicative of the magnitude of the transmitted current. In this case, the sensor control section 25 causes the current adjustment section 27 to change the transmission current based on the magnitude of the transmission current indicated by the receiver signal. The current limiting circuit 26 is, for example, a variable resistor, and the sensor control unit 25 transmits when the transmission current is greater than or equal to a first threshold (eg, α1 in FIG. 10) and less than a second threshold (eg, α3 in FIG. 10). The resistance value of the current limiting circuit 26 is adjusted so that the current reaches the second threshold. Current limiting circuit 26 may have multiple resistors and a switch for selecting one or more of the respective resistors.

Sensor control 25 may decrease the transmission current. For example, when the transmission current is equal to or greater than a third threshold (eg, α4 in FIG. 10) that is greater than the second threshold, the sensor control unit 25 controls the transmission current to be greater than or equal to the second threshold and less than the third threshold. The resistance value of the limiting circuit 26 may be adjusted. The sensor control unit 25 reduces the transmission current when the transmission current is greater than the reference value, thereby stabilizing the level of the receiver signal received by the receiver 1 and reducing power consumption. be able to.

[Operation flowchart of fire alarm system S]
FIG. 12 is a flow chart of the operation of the receiver controller 17 of the receiver 1 executing control for adjusting the transmission current. The receiver control section 17 first sets the address to 1 (S11), and transmits request information requesting transmission of a sensor signal to the sensor 2 of the address 1 (S12). The receiver controller 17 measures the transmission current while the sensor 2 of address 1 is transmitting the sensor signal (S13).

The receiver control unit 17 determines whether or not the measured transmission current is smaller than the minimum allowable value (eg α3 in FIG. 10) (S14). When the receiver control unit 17 determines that the measured transmission current is smaller than the minimum allowable value (YES in S14), it transmits request information for increasing the transmission current to the sensor 2 of address 1 (S15). ). When the receiver control unit 17 determines that the measured transmission current is equal to or greater than the minimum allowable value (NO in S14), it determines whether the measured transmission current is greater than the maximum allowable value (eg, α4 in FIG. 10). Determine (S16).

If the receiver control unit 17 determines that the measured transmission current is greater than the maximum allowable value (YES in S16), it transmits request information for decreasing the transmission current to the sensor 2 of address 1 (S17 ). When the receiver control unit 17 determines that the measured transmission current is equal to or less than the maximum allowable value (for example, α3 or more and α4 or less in FIG. 10), the request information is not transmitted to the sensor 2 of the address 1. , to S18.

Subsequently, the receiver control section 17 sets the next address as the address of the sensor 2 whose transmission current is to be adjusted (S18). The receiver control unit 17 determines whether or not the adjustment of the sensors 2 of all addresses has been completed (S19). If the adjustment of the sensors 2 of all addresses has not been completed (NO in S19), The processing up to S18 is repeated. When the adjustment of the sensors 2 of all addresses is completed (YES in S19), the receiver control section 17 ends the transmission current adjustment process.

FIG. 13 is a flow chart of the operation of the sensor controller 25 adjusting the transmission current. When the sensor control unit 25 receives the request information from the receiver 1 (S21), it identifies the content of the request information and determines whether or not the request information includes an instruction to increase the transmission current (S22). When the sensor control unit 25 determines that the request information includes an instruction to increase the transmission current (YES in S22), it activates the transmission current adjustment circuit (S23). In the case of the example shown in FIG. 11, the sensor control section 25 reduces the resistance value on the transmission path by turning on the switch 251 to increase the transmission current.

When the sensor control unit 25 determines that the request information does not include an instruction to increase the transmission current (NO in S22), it determines whether or not the request information includes an instruction to decrease the transmission current (S24). When the sensor control unit 25 determines that the request information includes an instruction to decrease the transmission current (YES in S24), the sensor control unit 25 stops the transmission current adjustment circuit (S25). In the case of the example shown in FIG. 11, the sensor control section 25 causes the switch 251 to be turned off to increase the resistance value on the transmission path and reduce the transmission current.

A resistor and a switch connected in parallel are further provided between the impedance element 223 shown in FIG. 11 and the ground so that the sensor control section 25 can further reduce the transmission current. good too. The sensor control unit 25 makes the switch conductive in a steady state. The sensor control unit 25 makes the switch non-conductive when it is necessary to reduce the transmission current, thereby increasing the resistance between the emitter of the transistor 222 and ground, thereby reducing the transmission current. can be done.

[Effect of fire alarm system S]
As described above, the receiver 1 measures the transmission current while the sensor 2 is transmitting the sensor signal, and if there is an abnormality in the transmission current, issues an alarm indicating that there is an abnormality. When the receiver 1 issues an alarm, the administrator of the fire alarm system S can quickly discover a failure of the transmission line T connecting the receiver 1 and the detector 2 .

Further, when the receiver 1 detects that there is an abnormality in the transmission current, the receiver 1 causes the sensor 2 to adjust the transmission current so that the transmission current becomes an appropriate value. By adjusting the transmission current in cooperation with the receiver 1 and the sensor 2, the wave height of the sensor signal received by the receiver 1 becomes a substantially constant value, so that the receiver 1 can correctly receive the sensor signal. You can increase your odds.

Further, since the wave height of the sensor signal received by the receiver 1 becomes a substantially constant value, the configuration of the receiving circuit of the receiver 1 can be simplified. In general, when the amount of variation in the amplitude and frequency of the transmission current is large, the receiving circuit often requires a complicated circuit configuration composed of multi-stage amplifiers such as active filter circuits. However, according to the present embodiment, it is possible to suppress fluctuations in the amplitude and frequency of the transmission current, thereby simplifying the receiving circuit.

[Modification]
In the above description, the receiver 1 monitors the transmission current while the sensor 2 is transmitting the sensor signal, and the sensor 2 increases the transmission current when the transmission current is small. In such a case, the receiver signal transmitted by the receiver 1 is also attenuated because the impedance of the transmission line T is too large. Therefore, the receiver control unit 17 may increase the transmission current when transmitting the receiver signal when determining that the transmission current is less than the threshold. As an example, the receiver 1 has a circuit such as the current adjustment section 27 shown in FIG. 11, and the receiver control section 17 switches a switch similar to the switch 251 in FIG. can be reduced, the transmission current can be increased.

Moreover, the sensor 2 has a transmission current measurement circuit equivalent to the transmission current measurement circuit 15 in FIG. If so, a sensor signal may be sent to the receiver 1 containing request information requesting an increase in current. In this case, the receiver controller 17 increases the transmission current in response to receiving the sensor signal.

The sensor control section 25 may send a sensor signal including the value of the transmission current measured by the transmission current measurement circuit to the receiver 1 . In this case, the receiver controller 17 increases or decreases the transmission current based on the value of the transmission current included in the received sensor signal.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist thereof. be. For example, specific embodiments of device distribution/integration are not limited to the above-described embodiments. can be done. In addition, new embodiments resulting from arbitrary combinations of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment caused by the combination has the effect of the original embodiment.

1 receiver 2 sensor 11 power supply circuit 12 user IF unit 13 reception circuit 14 transmission circuit 15 transmission current measurement circuit 16 voltage conversion circuit 17 receiver control unit 21 power supply circuit 22 transmission circuit 23 reception circuit 24 sensor circuit 25 sensor control unit 26 current limiting circuit 27 current adjusting units 141, 143, 151, 221, 223 impedance element 142 transistor 152 amplifier 222 transistor 251 switch

Claims (5)

A sensor that senses the occurrence of an abnormality in an installed area, and a receiver that receives a sensor signal transmitted by the sensor,
The sensor is
a sensor transmitter for transmitting the sensor signal;
a sensor controller that causes the sensor transmitter to transmit the sensor signal;
has
The receiver is
a current detection unit that detects a transmission current flowing through a transmission line connecting between the sensor and the receiver;
a receiver receiver that receives the sensor signal from the sensor;
a receiver transmitter for transmitting a receiver signal to the sensor;
receiver control for determining that there is an abnormality in the transmission line when the transmission current detected by the current detection unit while the receiver receiving unit is receiving the sensor signal is less than a predetermined threshold value; Department and
has
The sensor is
a sensor receiver that receives the receiver signal;
a current adjuster that adjusts the transmission current while transmitting the sensor signal;
further having
The receiver control unit causes the receiver transmission unit to transmit the receiver signal including request information for requesting the sensor to transmit the sensor signal, and causes the receiver signal to be transmitted. Later, the receiver receiving unit determines that there is an abnormality in the transmission line based on the transmission current while receiving the sensor signal, and if it is determined that there is an abnormality in the transmission line, the sensing causing the receiver transmitting unit to transmit the receiver signal including a current increase request requesting the device to increase the transmission current;
The sensor control unit causes the current adjusting unit to transmit the sensor signal while changing the transmission current when the sensor receiving unit receives the receiver signal including the current increase request. ,
Fire alarm system. The receiver control unit causes the receiver transmission unit to transmit the receiver signal indicating the magnitude of the transmission current detected by the current detection unit,
The sensor control unit causes the current adjustment unit to change the transmission current based on the magnitude of the transmission current indicated by the receiver signal.
The fire alarm system according to claim 1. The fire alarm system comprises a plurality of the sensors,
The receiver control unit causes the receiver transmission unit to transmit the receiver signal further including identification information for identifying each of the plurality of sensors,
The sensor further has a storage unit that stores its own identification information,
The sensor control unit controls the sensor transmission unit on the condition that the identification information included in the receiver signal received by the sensor reception unit matches the identification information stored in the storage unit. causing the sensor signal to be sent to
The fire alarm system according to claim 1 or 2. The receiver further has a display unit that displays an alarm indicating that there is an abnormality in the transmission line,
The receiver control unit controls the transmission current based on the transmission current while receiving the sensor signal from the sensor corresponding to the identification information included in the receiver signal transmitted by the receiver transmission unit. When it is determined that there is an abnormality in the transmission line, the alarm is displayed on the display unit together with information specifying the sensor corresponding to the identification information included in the receiver signal transmitted by the receiver transmission unit. ,
The fire alarm system according to claim 3. The receiver control unit
outputting a first type alarm when the transmission current is less than a first threshold;
outputting a second type of warning when the transmission current is equal to or greater than the first threshold and less than a second threshold larger than the first threshold;
Determining that the transmission current is normal when the transmission current is equal to or greater than the second threshold;
The fire alarm system according to any one of claims 1 to 4.

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