EVACUATION ALARM INTENDED TO WORK IN BUILDINGS AND SMALL REGIONS

Abstract: The invention relates to an evacuation alarm system for use in buildings and within small outdoor areas. The evacuation alarm comprises a two-way, digital transmission via a cable to allow the implementation of additional functions and, when power-consuming alarm components are used, also current supply to such components via the cable. The functions of the alarm component are controllable with the aid of a signal which is transmitted to the component in the shape of e.g. background music from a loudspeaker located therein, said sound being recuperable via a microphone or the like and reconverted to a signal which, preferably by correlation, is comparable with the original signal/background music.

Description: Evacuation alarm intended to work in buildings and small regions The present invention relates to an evacuation alarm system which is intended for use in buildings and within small outdoor areas and which comprises a new data network which, structurally and functionally, is similar to the telecommunication network but has been developed so that it can within small areas up to a few kilometers serve for the purpose of transmitting data and digital sound. In addition thereto, in order to simplify the installation and the operation, power supply has been integrated into the system. The data transmission is also used for the purpose of super- vising the system. The modular structure permits simple expansion, the addition of loop-shaped or star-shaped networks and the choice between external or internal current supply. Thanks to the fact that a supervision function has been implemented already from the outset, it has been possible to maintain and to secure the operational reliability of the system also during exceptional circumstances. Altogether this amounts to substantial advan- tages in comparison with analogous networks of prior art types. Normally, it is possible to upgrade existing, analogous networks to a system according to the invention without having to install a new cable. The base of the system is the centrally disposed network server, the main purpose of which is to formate incoming data to the protocol used in the network, to transmit and supervise data in the network and, when this is needed, to release an alarm. The server is available in different shapes and does normally cooperate with means for current supply, data multiplexing and studio equipment, if any. The receivers are so- called terminals which can have several functions in addition to the data reception and transmission proper. By way of example a terminal may communicate with other units, serve as a digital/analogous converter for the regeneration of sound or serve as an interface to other units etcetera. Accordingly, the object of the present invention is to provide an evacuation alarm system of the type above defined which in an excellent way satisfies its purposes, the system being at the same time very flexible and can be adapted to match most needs in respect of analogous and digital transmission. Also, it is possible to mix different groups of services without jeo- pardizing the operational reliability and function of the system. The invention will now be described in greater detail, reference being made to the annexed drawings, in which Fig. 1 is a block diagram illustrating an alarm unit forming part of the system according to the invention and Fig. 2 comprises two curve diagrams, the upper one indicating the power used in a thin cable and the lower one the transmitted, available average power in a cable having the same cross- sectional area. As far as the communication in the system is concerned the data transmission, which is completely digital, occurs in a block pattern at a medium-high speed. The communication is two-way and data are transmitted in a time-multiplex form. The system handles this completely internally and the transmission of the data becomes fully transparent to the user. As to the current supply, power from the network or from conventional power networks can be used directly or stored in the terminal. The system has integrated functions for the supervision of a mixed or completely decentralized current supply network. The system voltage can be selected in the range below 150 V but, normally, voltages higher than 50 V are not used. Several factors have been considered in order to simplify the installation, the final result being a pair conductor system which is independent of the polarity. The cross-sectional area of the cable does not affect the data transmission but, in systems where high power levels are to be transmitted, attention must be paid to the area. The system permits use of a loop-shaped or star-shaped network. Considering the safety aspect each terminal unit does, with the aid of its own computer, check that the communication is maintained and operates without any distur- bances, making it possible to create systems in which it is important upon interruption to reach a predetermined condition. Typical applications are evacuation alarm systems, liquid level control apparatus and equipment normally remote-controlled but capable of performing self-protecting functions. By addition of different programs to the terminal units it is possible to create more complex systems and, by definition in advance of the situations which may arise, the handling of those situations can be carried out locally in accordance with a predefined condition master. Typical applications involve activation of flash bulbs, fire cells, ventilation and heat supervision equipment. Thanks to a structured and hierarchically composed program new systems may conveniently be created which can profit from the basic modules integrated in the system. Complete software packages are available for the construction of evacuation alarm systems. The function of the evacuation alarm is governed by the correlation in the alarm unit of a normal signal/background music. In this way the solution according to the invention permits a complete control of the analogous and digital signal routes of the alarm unit and the result can be retransmitted to e.g. an alarm central unit acknowledging that the alarm is operable. Stated in other words it could be said that the alarm unit is provided with an acoustic feedback for self-checking. When the alarm unit is mounted in e.g. factory buildings having such acoustic conditions that there are generated echo signals or phase displacements, the above-mentioned polling function can be used to equa- lize and compensate the sound picture thereby improving its readability. The system can be continuously expanded in order to satisfy the existing different demands. However, it is compatible between the different versions due to the fact that the interfaces and the software are similar. In an exemplifying mixed system, operating with both analogous and digital technique, the system according to the invention does, however, always transmit data in the digital form. This guarantees that no types of analogous distortion can arise and that the system can be installed and put into operation with the use of simple means. An evacuation alarm of the type here concerned can also be activated both by a digital transmission and by the absence of transmission. When the transmission interruption control mode is used, the division into groups must take place in such a way that the proper selective activation is achieved. Generally, this is a case already when, according to the invention, old analogous systems are upgraded to the data network. When digital activation is used, individual group or general calls can be made without any restrictions. The terminal unit can operate as a "stand-alone" termi- nal with a "phantom" current supply. Since it is possible to transmit a high level power, it becomes possible to control e.g. magnetic valves, illumination, door locks or motors. By charging locally available batteries additional power can be made available tempo- rarily or during a power failure. The software can permit local decisions based on incoming signals from different sensors. Often there exists in the system a need for a two-way communication to certain spots. By way of example, entrance supervising systems can be mentioned in which there exists a need for both internal communication and for gate control. Another example is an evacuation alarm system in which it is desirable to transmit messages for either immediate use or for storing in the terminal unit. Activation of the alarm system can occur centrally or decentralized. In this way a transmission interruption in the network caused by e.g. fire will always trigger the alarm. A high reliability can be achieved by means of a local battery which is charged and supervised via the network. Various combinations can conveniently be made, it being by way of example possible to connect a flash bulb with a unit having a recorded evacuation message. When not activated, the system may produce e.g. background music. A back-up battery provides continuous information about the status of the sensors connected to the terminal unit and this only in case of a power failure. This may be important in certain types of supervision at which normally automatic functions can be replaced by manual control, when necessary. In other systems acoustic signals may be fed to a loudspeaker via a cable, the impedance of which must as a rule be low to avoid high losses in the cable. This problem is normally solved by the use of so-called line transformers which reduce the current intensity and increase the voltage. It is prior art in that connection to use a cable transmitting e.g. data signals and electric power together. This method is utilized by e.g. power distribution companies and in certain control systems etcetera. However, the power current flows through the cable from the outset, data signals being superimposed thereon etcetera. Should it be desirable in a cable having a certain cross-sectional area and forming part of a loud speaker system to increase the maximum power level that can be transmitted without the use of line transformers, the maximum power which then can be transmitted must be generated by a direct current. This power level can then cover considerably higher output power peaks than the average power value transmitted. In the system according to the invention the acoustic signal is in the shape of a "weak" signal superimposed upon the "power signal". Accumulated power can then feed the loud-speaker up to the peak value power output. The weak sound signal is amplified meaning that the drive stage is at the loud-speaker. The corresponding advantages are that, at the same output power, it will be possible to use a smaller cross-sectional cable area, that there will be no audio distortion in the cable (digital signal) and that a low voltage can be maintained in comparison with systems having line transformers in combination with loud-speakers. Consequently, in the alarm unit the direct current signal is separated from the superimposed signal in the way that the superimposed signal is detected in a receiver, whereupon the signal is fed to the amplifier for driving the loud-speaker.

Claims: Claims 1. Evacuation alarm system for use in buildings and within small outdoor areas, comprising a two-way, digital transmission via a cable to allow the implementation of additional functions and, when power- consuming alarm components are used, also current supply to such components via the cable, characterized in that the functions of the alarm component are con- trollable with the aid of a signal which is transmitted to the component in the shape of e.g. background music from a loud-speaker located therein, said sound being recuperable via a microphone or the like and reconverted to a signal which, preferably by correlation, is comparable with the original signal/background music. 2. An evacuation alarm system according to claim 1, characterized in that cables forming part of the alarm unit may exhibit a small area when an increase of the transmitted power is made by use of a direct current, said power being then useful for covering considerably higher output power peaks than the average value of the power transmitted in the alarm unit, e.g. a sound being transmitted as a weak signal superimposed on the power signal, said weak signal driving a loudspeaker via a receiver with an amplifier in the alarm unit for the purpose of making it possible in said alarm unit to separate said direct current signal from said superimposed signal by detecting said superimposed signal in a receiver, whereupon the signal is supplied to said amplifier to drive said loud-speaker.

Inventors: PONTRAM NILS, PONTRAM, NILS
Applicants: LANCAP AB, PONTRAM NILS, PONTRAM, NILS
Application year: 1998
Main classification: G08B26
IPC codes: G08B7, G08B29