GB2476587A - Control system with extended control signal - Google Patents

Abstract

In a data transmission system, e.g. a fire alarm system for a premises, a control device and a plurality of terminal devices e.g. sensors are connected to each other through transmission path (Fig.1, not shown). A pulse signal composed of a data string is transmitted between the control device and the terminal devices. The string includes a start bit ; a mode region indicating whether the signal is for collecting data from or controlling the terminal devices; an address region designating one or more terminal device(s); a command region comprising a command for the selected terminal devices; a return data region for terminal devices to return data to the control device, and a stop bit (Fig.3A, not shown). The string may be expanded by replacing the stop bit with an extension bit (A6), followed by an extra data return region (A7) and a stop bit (A8), so that terminal devices with increased capabilities can return extra data without affecting the operation of the conventional devices.

Description

DATA TRANSMISSION SYSTEM AND MONITORING SYSTEM

The disclosure of Japanese Patent Application No. 2009-293905 filed on December 25, 2009 including specification, drawings and claims is incorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a data transmission system using a transmission path, and more particularly to a technology that is effectively applied to data transmission in a monitoring system, such as a fire protection system, a security system, and the like.

In a fire protection system provided with a monitoring device (receiver) which is installed in, for example, a building, a factory, or an event site to monitor the occurrence of disasters such as fire and the like by receiving detected signals from a heat detector, a smoke detector, and a gas leak detector, the monitoring device (receiver) and a plurality of detectors are connected to each other with a transmission path to transmit the detected signals therethrough.

In this structure, the length of the transmission path is likely to become extremely long. It is preferable to reduce the number of transmission lines for transmitting signals and the number of power lines for supplying power in the system.

Accordingly, a two-line data transmission system is practically used in a monitoring system illustrated in Fig. 7, that monitors the occurrence of disasters such as fire and the like by receiving detected signals from a heat detector, a smoke detector, a gas leak detector, and the like.

In this data transmission system, a monitor device (receiver) and a plurality of terminal devices such as detectors and repeaters are connected to each other via a transmission path which is composed of two transmission lines to supply power and transmit signals through the transmission path, simultaneously.

For example, in such a two-line data transmission system, as disclosed in JP-A-60-028341, digital data is transmittedlreceived by defining "0" and "1" in a binary signal as waveforms (pulses) illustrated in Figs. 8B and 8C and connecting a number of the pulses to generate a pulse string illustrated in Fig. 8A.

Specifically, a region indicated by a mark T in Fig. 8A denotes a transmission data region for addresses, commands and the like to be transmitted from the monitoring device (receiver) to the terminal device, and a region indicated by a mark R in Fig. 8A denotes a return data region from the terminal device. Although the technical term "region" is used in this specification, it is also referred to as "segment" or "field" in the art. When returning the data, the monitoring device (receiver) successively outputs a signal that indicates "1" as illustrated in Fig. 8C, and the terminal device controls whether to make a current flow through the transmission lines during a period in which a signal descends to a low level. In Fig. 8A, a portion indicated by slant lines denotes a state where a current flows through the transmission lines, and the monitoring device (receiver) detects this state, so that data of "0" and "1" can be received.

Recently, with large-sized buildings, diversification of detectors, large-sized fire protection systems, and high-performance systems, the amount of information that is desirable for the monitoring device (receiver) to collect from the terminal device side is increasing.

However, in the data transmission system disclosed in JP-A-60-028341, the return data region R is composed of a small number of bits and has no extension property, and thus only data that can be represented by a small number of bits can be transmitted. Because of this, it is difficult to apply the data transmission system of JP-A-60-02834 1 to the large-sized and high-performance fire protection system in which the number or classifications of detectors is increased. As a result, if a large-sized or high-performance fire protection system is used, it is necessary to replace all of the monitoring device (receiver) and the terminal devices with new ones, and this causes a sharp increase in cost.

SUMMARY

It is therefore an object of at least one embodiment of the present invention to provide a data transmission system and a monitoring system. in which a terminal device corresponds to a new data transmission system can be added and connected to the existing transmission lines corresponds to a conventional data transmission system while remaining the existing terminal devices correspond to the conventional data transmission system to collect data.

In order to achieve the above described object, according to an aspect of at least one embodiment of the present invention, there is provided a data transmission system in which a control device and a plurality of terminal devices are connected to each other through a transmission path and a pulse signal composed of a data string is transmitted between the control device and each of the terminal devices, wherein the data string has a structure in which a mode region that stores information indicating whether the data string is for collecting data or for controlling one or more of the terminal devices, an address storage region that stores information for designating one or more of the terminal devices, a command region that stores information indicating contents of a command for one or more of the terminal devices, and a return data region in which return data is to be stored are arranged between a start bit and a stop bit which is replacable by an extension bit corresponding to a waveform different from a waveform to which the stop bit corresponds, and wherein an extended return data region in which extended return data is to be stored is added following the extension bit when the stop bit is replaced by the extension bit.

According to a second aspect of at least one embodiment of the present invention, there is provided a monitoring system comprising a monitoring device and a plurality of terminal devices connected to a transmission path extended from the monitoring device, the monitoring system is configured to transmit a pulse signal composed of a data string between the monitoring device and the terminal devices through the transmission path, wherein the data string has a structure in which a mode region that stores information indicating whether the data string is for collecting data or for controlling one or more of the terminal devices, an address storage region that stores information for designating one or more of the terminal devices, a command region that stores information indicating contents of a command for one or more of the terminal devices, and a return data region in which return data is to be stored are arranged between a start bit and a stop bit which is replacable by an extension bit corresponding to a waveform different from a waveform to which the stop bit corresponds, and wherein the monitoring device transmits the data string in which an extended return data region in which extended return data is to be stored is added following the extension bit when the stop bit is replaced by the extension bit.

According to the first or second aspect of at least one embodiment of the present invention, the stop bit can be replaced by the extension bit. If a terminal device has a function of discriminating the extension bit, the data string can be extended. Since the extended return data region can be added to the data string having the extension bit, a large amount of data which is unable to be transmitted by the conventional terminal device, can be transmitted. Thus, it is possible to add and connect a terminal device which corresponds to a new data transmission' system to the existing transmission lines which correspond to a conventional data transmission system while remaining the existing terminal devices which correspond to the conventional data transmission system to collect data. It is possible to expand the scale of the already installed monitoring system or to make it high-performance only by partially reconstruct the system.

There is no need to entirely replace the devices used in the system by new ones, and thus the increase in cost can be avoided.

In the data transmission system, a waveform in the return data region may be changed in accordance with the return data returned from one or more of the terminal devices, and a waveform in the extended return data region may be changed in accordance with the extended return data returned from one or more of the terminal devices.

In the monitoring system, a waveform in the return data region of the data string which is transmitted from the monitoring device through the transmission path may be changed in accordance with the return data which one or more of the terminal devices returns, and a waveform in the extended return data region of the data string which is transmitted from the monitoring device through the transmission path may be changed in accordance with the extended return data which one or more of the terminal devices returns.

With the above configuration, since the waveform of the data string in the return data region and the extended return data region is changed according to the data that is returned from the terminal device, it is possible to easily realize the function of supplying the power together with the data string through the transmission path.

In the data transmission system, the return data region may include a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the return data is to be stored, the data region arranged between the head region and the end region, and the extended return data region may include a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the extended return data is to be stored, the data region arranged between the head region and the end region.

In the monitoring system, the return data region may include a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the return data is to be stored, the data region arranged between the head region and the end region, and the extended return data region may include a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the extended return data is to be stored, the data region arranged between the head region and the end region.

With the above configuration, since the sub-start bit and the sub-stop bit are added to the head region and the end region of the return data region and the extended return data region by the terminal device, the monitoring device can reliably detect that the terminal device responds, which can correspond to the data range in the return data region and the extended return data region and the data string including the extension bit.

In the data transmission system, the information stored in the mode region may be represented by a first pulse waveform or a second pulse waveform which have the same time length and different waveforms, and the stop bit may be represented by the same waveform as the first pulse waveform and the extended bit may be represented by the same waveform as the second pulse waveform.

In the monitoring system, the information stored in the mode region may be represented by a first pulse waveform or a second pulse waveform which have the same time length and different waveforms, and the stop bit may be represented by the same waveform as the first pulse waveform and the extended bit may be represented by the same waveform as the second pulse waveform.

With the above configuration, since the waveform for representing the information stored in the mode region and the waveform for representing the stop bit and the extension bit can be used in common, it is not necessary to generate various types of the waveform, and thus a burden of the control device or the monitoring device can be reduced. Also, since the number of the types of the waveform is small, it becomes possible to increase the data return speed by shortening the time length of a unit waveform.

According to the aspects of at least one embodiment of the present invention, a data transmission system and a monitoring system in which a terminal device corresponds to a new data transmission system can be added and connected to the existing transmission lines corresponds to a conventional data transmission system while remaining the existing terminal devices correspond to the conventional data transmission system to collect data can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings: Fig. 1 is a schematic diagram illustrating a system configuration of a monitoring system to which a data transmission system is applied according to an embodiment of the present invention; Fig. 2 is an explanatory diagram illustrating definition of waveforms that form a data string used for transmitting data in the monitoring system according to the embodiment; Figs. 3A to 3C are explanatory diagrams illustrating examples of a data string that is used for transmitting data to a conventional terminal device in the monitoring system according to the embodiment; Figs. 4A and 4B are explanatory diagrams illustrating examples of a data string that is used for transmitting data to a terminal device having new functionality in the monitoring system according to the embodiment; Fig. 5 is a flowchart illustrating a data transmission processing procedure by the conventional terminal in the monitoring system according to the embodiment of the present invention; Fig. 6 is a flowchart illustrating a data transmission processing procedure by the terminal device having new functionality in the monitoring system according to the embodiment; Fig. 7 is a schematic diagram illustrating a system configuration of a conventional monitoring system; Fig. 8A is an explanatory diagram illustrating a data string used for transmitting data in the conventional monitoring system; and Figs. 8B and 8C are explanatory diagrams illustrating definition of waveforms that form a data string used for transmitting data in the conventional monitoring system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 illustrates an embodiment in which the present invention is applied to a fire monitoring system (this is also referred to as a fire detection and alarm system in the art) as an example. The fire monitoring system according to this embodiment includes a receiver 10 (this is also referred to as a control panel or a fire alarm control panel in the art) as a control device or a monitoring device, repeaters 30A and 30B (the repeater is also referred to as an input output module in the art) connected to the receiver 10 through a transmission path 20, and heat detectors 41A and 41B, smoke detectors 42A and 42B, and a smoke exhausting damper 43, which are connected to the repeaters 30A and 30B, respectively. Also, the heat detectors 41 A and 41 B and the smoke detectors 42A and 42B may be directly connected to the receiver 10 via the transmission path 20 without passing through the repeaters 30A and 30B.

Although not clearly illustrated in Fig. 1, the transmission path 20 is composed of two transmission lines through which signals are transmitted and the power is supplied. In this embodiment, a device that is connected to the receiver 10 as the monitoring device via the transmission path 20 so as to transmit data is generally called a terminal device. Accordingly, not only a detector but also a repeater is a terminal device. In the fire monitoring system, a press button type transmitter, which is manipulated by a person to notify the occurrence of an abnormality, may be connected to the transmission path 20. Also, as a terminal device connected to a smoke defense repeater, a door ejector, a fireproof shutter, or the like, may be used.

In Fig. 1, the reference numeral "41 A" denotes a conventional type heat detector, "42A" denotes a conventional type smoke detector, "41B" denotes a heat detector having new functionality, which can perform extended transmission according to the data transmission system of the embodiment of the present invention, and "42B" denotes a smoke detector having new functionality, which can perform the extended transmission. As illustrated in Fig. 1, in the fire monitoring system according to the embodiment of the present invention, the conventional detectors and the detectors having the new functionality, which can perform the extended transmission are connected to the transmission path 20 and thus the fire monitoring system can perform data transmission even when old and new detectors coexist in the system.

The receiver 10 shown in Fig. 1 is a receiver having new functionality, which can perform the extended transmission according to the data transmission system of the embodiment of the present invention. Also, when a detector having new functionality is connected to a repeater, the repeater 30B having new functionality, which can perform the extended transmission is used instead of the conventional type repeater 30A.

A nonvolatile memory provided in the receiver 10 stores a table in which addresses of all repeaters 30A and 30B and detectors 41A, 41B, 42A, and 428 and information that indicates the classification of devices (with discrimination between old and new ones) are stored. The receiver 10 can perform the transmission of data (including a control command) with the respective terminal devices by polling or addressing using the addresses stored in the table.

Next, data transmission to the conventional type terminal devices 30A, 41A, and 42A and data transmission to terminals 30B, 4lB, and 42B having new functions, by the receiver (monitoring device)1O, will be described in detail.

Figs. 3A to 3C and 4A and 4B illustrate examples of the data string that is used for transmitting data in the monitoring system according to the embodiment of the present invention, and Fig. 2 illustrates definition of a unit waveform that constitutes the data string in Figs. 3A to 3C and 4A and 4B. In Figs. 3A to 3C and 4A and 4B, the waveforms indicated by dotted lines mean that bit data to be transmitted is not predetermined, and any one of "0" and "1" is input according to the data to be transmitted or returned, and the waveforms indicated by hatching means that the data returned from the terminal device side is "1". The system that transmits and returns the data and at the same time, supplies the power via the two transmission lines can be implemented by a related art such as an invention disclosed in JP-A-60-028341 as described above, and thus the explanation thereof will be omitted.

The data string illustrated in Figs. 3A to 3C and 4A and 4B is basically output from the receiver 10. Figs. 3A to 3C illustrate the data strings that are used for transmitting data with the conventional type terminal device.

Fig. 3A illustrates the data string that is used by the receiver 10 to collect classification information from the respective terminal devices, Fig. 3B illustrates the data string that is used to collect information (in the description, it is called analog data) on the subject of monitoring such as the terminal device state, detection amount, and the like, and Fig. 3C illustrates the data string that is used by the receiver 10 to control the respective terminal devices by sending a command to the terminal devices.

As illustrated in Fig. 3, the transmission data string used in this embodiment includes a head region Al that stores a start bit that becomes a start pulse on the transmission path, a mode region A2 that stores information that indicates whether the data string is for collecting data or for controlling the terminal device, an address region A3 that stores information indicating an address which is the identification information of the terminal device, a command region A4 that stores information indicating the contents of a command for the terminal device, a return data region A5 that stores return data, and an end region A6 that stores a stop bit that becomes a stop pulse on the transmission path.

In the address region A3, an address and a parity bit for error check are stored. In the command region A4, a command code, a parity bit, and a command end bit that indicates a command end are stored. In the return data region AS, a return start bit (sub-start bit), data that is returned from the terminal device to the receiver, a parity bit, and a return stop bit (sub-stop bit) are stored.

The waveform of the return data region A5 output from the receiver 10 is a repetition of "0" as illustrated in (B) of Fig. 2, and this waveform is changed as indicated by hatching or a dotted line as illustrated in Figs. 3A to 3C and 4A and 4B in accordance with the data that is returned from the terminal device. This change of the waveform is directly or indirectly detected by the receiver, and thus the data output from the terminal device can be recognized.

The return start bit at the head region of the return data region A5 and the return stop bit at the end region of the return data region AS are set to necessarily output "1" by the terminal device.

Accordingly, the receiver monitors these bits, and if it is not "1", the receiver may process it as a transmission error.

In the data string of Fig. 3C that is used for sending a command from the receiver 10 to the terminal device, the return data region A5 may be omitted. Even in this case, the return stop bit may be provided. Also, in the data string of Fig. 3C, by providing the return data region AS, the data string has the same configuration as other data strings. Thus, the processing procedure of the data string of Fig. 3C can be in common with that of the other data strings to simplify its design. If the return data region A5 is omitted in the data string of Fig. 3C, the transmission from the receiver to the terminal may be considered as access by addressing. In this case, information of the mode region A2 may be considered as information indicating whether the transmission from the receiver 10 corresponds to polling or addressing.

Fig. 4A illustrates a data string that is used by the receiver 10 to collect terminal classification information from a terminal device having new functionality, and Fig. 4B illustrates a data string that is used by the receiver 10 to collect information on the subject of monitoring, such as a terminal state and a detected amount, from a terminal device having new functionality. Since the data string that is used by the receiver 10 to send a command to the terminal device having new functionality to control the terminal device is the same as the data string for the conventional type terminal as illustrated in Fig. 3C, the illustration and explanation thereof will be omitted.

As illustrated in Figs 4A and 4B, from the head region Al in which a start bit is stored, to the return data region A5 in which return data is stored, the data string that is to be transmitted to the terminal device having new functionality is the same as the data string for the conventional type terminal device. On the other hand, the waveform that is stored in the end region A6 is different from the waveform that is stored in the end region A6 of the data string for the conventional type terminal illustrated in Figs. 3A and 3B. Specifically, while the waveform (stop bit) of the end region A6 in the data string for the conventional type terminal device is the same as the waveform of"l" as illustrated in (A) of Fig. 2, the waveform that is stored in the end region A6 in the data string that is to be transmitted to the terminal device having new functionality is the same as the waveform of "0" as illustrated in (B) of Fig. 2 that is different from the waveform as illustrated in (A) of Fig. 2.

The receiver 10 is configured to transmit the data string, in which the extended return data region A7 and the end region A8 in which the stop bit is stored are added following the region A6 that stores the waveform of (B) of Fig. 2, to the terminal device having new functionality. The extended return data region A7 is similar to the return data region AS in the data string for the conventional type terminal device, and stores a return start bit, data that is returned from the terminal device to the receiver, a parity bit, and a return stop bit. The waveform of the stop bit that is stored in the end region A8 is the same as the waveform ("1" in (A) of Fig. 2) of the stop bit stored in the end region A6 of the data string for the conventional type terminal device. Since the return start bit and the return stop bit are added to the head and the end of each of the return data region AS and the extended return data region A7, the receiver as the monitoring device, can reliably detect that a terminal device is responding, which can correspond to the data string that includes the data range and the extension bit in the return data region and the extended return data region.

As the return data which is to be stored in the extended return data region A7 of the data string (see Fig. 4A) that includes the classification information collection command, for example, in the case where a code that indicates a "repeater" as a classification is stored in the return data region AS, a code that discriminates between a "repeater for fire reporting" and a "repeater for smoke defense" may exist. In the same manner, in the case where a code that indicates a "heat detector" or a "smoke detector" as the classification is stored in the return data region AS, a code that discriminates between the detectors having different detection methods or functions may be stored and returned.

The terminal device having new functionality has a function of detecting the data string output from the receiver 10 to the transmission path 20 and discriminating whether the waveform contained in the region A6 is the waveform as illustrated in (A) of Fig. 2 or the waveform as illustrated in (B) of Fig. 2, and if the waveform in the region A6 is the waveform as illustrated in (B) of Fig. 2, the terminal device performs a process of carrying return data on the waveform in the extended return data region A7 that follows the region A6. That is, the waveform contained in the region A6 as illustrated in (B) of Fig. 2 functions as the data extension signal (extension bit) for the terminal device having new functionality.

On the other hand, in the case where the waveform contained in the region A6 is the waveform as illustrated in (A) of Fig. 2, the terminal having new functionality ends the data return process at a time point where the waveform is detected. Since the conventional type terminal device connected to the transmission path 20 does not have a function of discriminating whether the waveform contained in the region A6 is the waveform as illustrated in (A) of Fig. 2 or the waveform as illustrated in (B) of Fig. 2, it performs the same operation as that in the case where the data string as indicated in Figs. 3A and 3B is transmitted even if the data string as indicated in Figs. 4A and 4B is transmitted thereto. That is, the conventional type terminal device sends no response with respect to the region A6 and the region A7.

Fig. 5 illustrates a data transmission processing procedure in the conventional type terminal device. The conventional type terminal device continuously monitors signals on the transmission line, and if a signal is input, it first determines whether the signal is a start bit (start pulse) (step Si). Here, if it is determined that the signal is not the start bit ("No"), the conventional type terminal device ends the process without performing any process. If it is determined that the signal is the start bit ("Yes"), the conventional type terminal device discriminates whether the mode refers to information collection by checking the waveform in the mode region A2 in step S2.

If it is determined that the mode is the information collection mode ("Yes") in step S2, the terminal device determines whether an address contained in the address region A3 coincides with the address that is allocated to the terminal device itself (step S3). Here, if it is determined that the address does not coincide with its address ("No"), the terminal device ends the process.

If it is determined that the address coincides with its address ("Yes"), the terminal device determines whether the command is a command for the collection of analog information such as the terminal device state or the like by checking the waveform in the command region A4 in step S4.

If it is determined that the command is the information collection command ("Yes") in step S4, the terminal device performs the process of preparing analog data to be returned (step S6) and the process of outputting the prepared return data (step S7), and returns to step Si.

On the other hand, if it is determined that the received data string is not the command for the collection of analog information from the waveform in the command region A4 ("No") in step S4, the terminal device proceeds to step Si 0, and detennines whether the command is a command for the collection of the classification information. Here, if it is determined that the command is the classification information collection command ("Yes"), the terminal device performs the process of outputting the return data (classification code) (step Si 2), and returns to step Si.

Also, if it is determined that the mode is not the information collection mode from the waveform in the mode region A2 ("No") in step S2, the terminal proceeds to step S15, and determines whether the mode is a terminal control mode. Here, if it is determined that the mode is not the terminal control mode ("No"), the terminal device ends the process. If it is determined that the mode is the terminal control mode ("Yes"), the terminal device determines whether the address contained in the address region A3 coincides with the address that is allocated to the terminal device itself (step Si 6). If it is determined that the address does not coincide with its address ("No"), the terminal device ends the process. If it is determined that the address coincides with its address ("Yes"), the terminal device generates and outputs a control signal in the terminal device according to the control command in the command region A4 in step Si 7. Then, the terminal performs the process of outputting the received control command as the return data (step Si 8), ends the process, and then returns to step Si.

Fig. 6 illustrates a data transmission processing procedure in a terminal device having new functionality. The difference between the flowchart of Fig. 6 and the flowchart of Fig. 5 is that the flowchart of Fig. 6 includes a process (step S8) of determining whether an extension signal (extension pulse) exists in the data string after the return data output process in step S7 in the flowchart of Fig. 5, a process (step S9) of adding and outputting the return data when it is determined that the extension signal exists in step S8, a process (step Si 3) of determining whether an extension signal exists following the return data region A5 in the data string after the return data output process in step Si2 in the flowchart of Fig. 5, and a process (step S14) of adding and outputting the return data when it is determined that the extension signal exists in step S13. Otherwise, the process is the same as the process in the flowchart of Fig. 5, and thus the duplicate explanation thereof will be omitted.

As described above, the terminal device having new functionality has a function of determining whether the extension signal exists following the return data region A5 in the data string and a function of adding and outputting the return data when it is determined that the extension signal exists. On the other hand, the conventional type terminal device does not have such a function. Thus, even in the case where the conventional type terminal device and the terminal device having new functionality coexist on the same transmission path 20 and are connected together, any terminal devices are able to perform the data transmission normally.

Also, since the conventional type terminal device and the terminal device having new functionality perform the above-described process in response to the data transmission from the receiver 10, the receiver 10 can detect a connection error based on a response to the classification information collection command from the terminal device in the case where the addresses registered in the table stored in the receiver 10, information indicating the terminal classification, and classification information collected from the terminal device through the transmission path 20 do not coincide with each other.

Specifically, for example, if the conventional type terminal device is connected to a point (address), to which the terminal device.having new functionality should be connected, the conventional type terminal device does not respond to the extended data region even though the receiver 10 outputs the data string to which the extension signal has been added, and thus the receiver 10 can detect that the tenninal device having new flmctionality is not connected. Also, even in the case where the terminal device responds to the extended data region, the receiver 10 can detect the connection error if the returned classification information is different from the data in the table that is maintained in the receiver 10.

In the terminal device having new functionality, the processes according to the flowcharts of Figs. 5 and 6 may be suitably changed if necessary. That is, during a typical monitoring operation, the data collection and control may be performed through transmission of a non-extendable data string as illustrated in Figs. 3A to 3C, and the system to which the embodiment of the present invention is applied can perform such a process.

Although the present invention has been described in detail based on the embodiments, the present invention is not limited to the above-described embodiments. For example, although the system in which the heat detectors and the smoke detectors are used is described in the embodiments, the fire detector is not limited to those described above. Diverse detectors, such as an ion-type fire detector, a complex fire detector that can simultaneously detect heat and smoke, a fire detector using a pyroelectric element, and the like, may be connected to the transmission path. Also, the arrangement of the regions of the data string that is transmitted through the transmission path is not limited to that illustrated in Figs. 3A to 3C or 4A and 4B, and for example, the address storage region and the mode region may be arranged in reverse order.

Further, in the above-described embodiments, although the conventional type terminal device and the terminal device having new functionality coexist in the system, the conventional type terminal device may be considered as a low-function device and the terminal having new functionality may be considered as a high-function device. That is, in the case of installing a monitoring system in a new building or the like, a system in which low-function devices and high-function devices coexist may be constructed, and through this, the cost of the whole system can be suppressed. Also, since it is possible to operate the new high-function device as an old-fashioned low-function device, a detector maker can continuously provide old-fashioned low-function devices as its products, and thus the stock of the old-fashioned devices can be reduced during the transition from old-fashioned devices to new devices.

Also, in the above-described embodiments, although the examples show that the return data region A5 is extended in the data string to be transmitted, the address region A3 can also be extended by applying the same method even in the case where it is desired to extend the address region A3. Accordingly, a monitoring system having many more terminal devices (for example, 256 or more terminal devices) can be constructed on a single transmission path.

In the foregoing description, although the examples show that the present invention is applied to a fire monitoring system, the present invention can be widely used in fire protection systems further including gas leak detectors for detecting noxious gases such as CO as a detector, security systems including moving object detectors, and other monitoring systems, and in cases of transmitting data between a control device and a plurality of terminal devices which are relatively far apart from the control device.

Claims (8)

1. What is claimed is: 1. A data transmission system in which a control device and a plurality of terminal devices are connected to each other through a transmission path and a pulse signal composed of a data string is transmitted between the control device and each of the terminal devices, wherein the data string has a structure in which a mode region that stores information indicating whether the data string is for collecting data or for controlling one or more of the terminal devices, an address storage region that stores information for designating one or more of the terminal devices, a command region that stores information indicating contents of a command for one or more of the terminal devices, and a return data region in which return data is to be stored are arranged between a start bit and a stop bit which is replacable by an extension bit corresponding to a waveform different from a waveform to which the stop bit corresponds, and wherein an extended return data region in which extended return data is to be stored is added following the extension bit whenthe stop bit is replaced by the extension bit.
2. 2. The data transmission system as set forth in claim I, wherein a waveform in the return data region is changed in accordance with the return data returned from one or more of the terminal devices, and wherein a waveform in the extended return data region is changed in accordance with the extended return data returned from one or more of the terminal devices.
3. 3. The data transmission system as set forth in claim 1, wherein the return data region includes a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the return data is to be stored, the data region arranged between the head region and the end region, and wherein the extended return data region includes a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the extended return data is to be stored, the data region arranged between the head region and the end region.
4. 4. The data transmission system as set forth in any one of claims 1 to 3, wherein the information stored in the mode region is represented by a first pulse waveform or a second pulse waveform which have the same time length and different waveforms, and wherein the stop bit is represented by the same waveform as the first pulse waveform and the extended bit is represented by the same waveform as the second pulse waveform.
5. 5. A monitoring system comprising a monitoring device and a plurality of terminal devices connected to a transmission path extended from the monitoring device, the monitoring system is configured to transmit a pulse signal composed of a data string between the monitoring device and the terminal devices through the transmission path, wherein the data string has a structure in which a mode region that stores information indicating whether the data string is for collecting data or for controlling one or more of the terminal devices, an address storage region that stores information for designating one or more of the terminal devices, a command region that stores information indicating contents of a command for one or more of the terminal devices, and a return data region in which return data is to be stored are arranged between a start bit and a stop bit which is replacable by an extension bit corresponding to a waveform different from a waveform to which the stop bit corresponds, and wherein the monitoring device transmits the data string in which an extended return data region in which extended return data is to be stored is added following the extension bit when the stop bit is replaced by the extension bit.
6. 6. The monitoring system as set forth in claim 5, wherein a waveform in the return data region of the data string which is transmitted from the monitoring device through the transmission path is changed in accordance with the return data which one or more of the terminal devices returns, and wherein a waveform in the extended return data region of the data string which is transmitted from the monitoring device through the transmission path is changed in accordance with the extended return data which one or more of the terminal devices returns.
7. 7. The monitoring system as set forth in claim 5, wherein the return data region includes a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the return data is to be stored, the data region arranged between the head region and the end region, and wherein the extended return data region includes a head region to which a sub-start bit is added by one or more of the terminal devices, an end region to which a sub-stop bit is added by one or more of the terminal devices and a data region in which the extended return data is to be stored, the data region arranged between the head region and the end region.
8. 8. The monitoring system as set forth in any one of claims 5 to 7, wherein the information stored in the mode region is represented by a first pulse waveform or a second pulse waveform which have the same time length and different waveforms, and wherein the stop bit is represented by the same waveform as the first pulse waveform and the extended bit is represented by the same waveform as the second pulse waveform.