Public address systems in the field of transport
In accordance with the Order of the President of the Russian Federation, activities have begun to introduce the Safe City APK in all regions of Russia. For governors, this direction is one of the priorities in their activities.
On December 03, 2014, the Decree of the Government of the Russian Federation No. 2446 approved the Concept for the construction and development of the AIC "Safe City", which involves the implementation of a unified systems approach to ensuring integrated security and includes: security of the population; transport safety; coordination of the work of emergency services and departments.
Each of us has heard ads in trolleybuses, electric trains, at bus stations, railway stations, subways, airports more than once. All these announcements are made by public address systems.
Warning systems have the most wide application in almost all spheres of human activity, including in the field of transport. In the field of transport are built:
Emergency notification systems;
Sound information systems;
Public address systems.
Emergency notification systems
The main purpose of the emergency warning system is to alert people about the danger that threatens them in the event of fires, emergencies, man-made disasters, natural disasters, terrorist threats, and to provide them with information related to their personal safety.
Warning systems are a mandatory component of almost any security system, in which they are the final executive element - an intermediary between technical means and man. To ensure the safety of buildings, warning and evacuation control systems are being built, which are a set of organizational measures and technical means aimed at ensuring the safety of people. These systems are subject to high regulatory requirements, as well as customer requirements that determine the specifics of their application.
By regulatory requirements the alert system should be:
highly reliable - to function for a long time;
automatic - turn on automatically without operator intervention;
controlled - to be able to automatically control all nodes (blocks) of the system;
redundant - in the event of a power failure, it must function for the time necessary to complete the evacuation.
A modern warning system is inherent in the requirement of integration with other systems and complexes, achieved by the introduction and use of digital technologies, which allow docking both at the protocol and physical levels.
Sound information systems
Sound information systems are inherently very simple. Audio information from a microphone or a source of pre-recorded audio messages is fed to an amplifier, where it is amplified and transmitted to a loudspeaker line. In more complex tasks, for example, at airports, a system is used that is a complex information and technical complex that operates under the control of software serviced by several operators and engineers. From the point of view of technical implementation, such systems are built as multi-channel and multi-priority systems. Very high demands are placed on these systems in terms of functionality and sound quality.
Multi-priority systems
Multi-priority systems allow you to broadcast information that differs in degree of importance - emergency signals, fire warning, service messages, informational (advertising) announcements, sometimes background music. In this case, the high-priority signal must interrupt or mute the low-priority signal.
Multichannel systems
Multichannel systems allow simultaneous or separate transmission of sound and speech information to different zones via separate channels.
Public address systems
An example of a public address system is the system used in electric trains, where the so-called. half-duplex direct channel system - a communication channel of subscriber panels installed in each car, with a driver's communication selector. The return channel is a loudspeaker (sound amplification) system with all the cars at the same time.
The public address system is intended:
for operational communication of the passenger with the driver in order to transmit any emergency message through the built-in calling panel of the communication system (located: in the middle of the car: in the subway; at the end of the car in railway electric trains);
to transmit information from the driver to the passengers.
Sound information from the driver is transmitted from a microphone or sound source and broadcast simultaneously to all loudspeakers installed in the cars of the electric train.
The systems discussed above are emergency warning systems, therefore, they are (in equal measure) subject to high quality and reliability requirements.
Consider some aspects of the operation and design of these systems.
Basic principles for building warning systems
Warning systems are classified according to various criteria. According to the method of transmitting information, warning systems are divided into wireless and wired. The wired method of transmitting audio information is the simplest and most reliable in terms of design, installation and maintenance. Public address systems that transmit sound information over wires are called broadcast systems. The functioning of the broadcasting system is based on the principle of three-stage transformation, which implements the stage-by-stage transmission of a speech message from the source (speaker) to the recipient (listener), Fig.1.
Fig.1 - Stages of electroacoustic conversion
At the first stage, the acoustic energy at the input of the system is converted into a low-level electrical signal at the output. This function performs an acoustic-electric converter - a microphone. At the second stage, amplification and conversion of the electrical signal is carried out. This function is performed by a sound amplification system, for example, a broadcast amplifier, Fig. 2
Fig.2 - Appearance broadcast amplifier ROXTON MZ-120
At the third stage, the electrical signal is converted into an audible acoustic signal at the output of the entire system. This function is performed by the loudspeaker.
General aspects of the design of warning systems
The quality of the reproduced speech message is determined by the parameters and coordination of all three components - a microphone, an amplifier and a loudspeaker. This condition is necessary, but not sufficient to ensure the perceived sound quality. To ensure the latter, an organizational measure called electroacoustic calculation is necessary. Electroacoustic calculation is performed at the initial stage of design, and to a large extent determines the parameters of the system being designed. During the design process, sound pressure is calculated at certain points, for which actual noise levels are measured, noise sources are identified, expected noise levels are determined, parameters, number and layout of loudspeakers are determined to ensure proper sound quality. Acoustic calculation involves the analysis of sound propagation conditions indoors or outdoors, takes into account many additional factors of a psycho-acoustic nature.
According to existing standards, the warning system must reproduce sound information in certain ranges:
approximately 100Hz to 16kHz, in the frequency range;
approximately 75dB to 130dB, in dynamic range,
broadcast it, if possible, on long distances with minimal loss and distortion. The most important element of the warning system, the parameters of which must be taken into account in the electroacoustic calculation, is the loudspeaker.
A little about loudspeakers
Loudspeakers are used in all areas and areas in which loud notification of people is carried out. The loudspeaker is the main executive element of any public address system and largely determines the sound quality. The most important parameter that determines sound quality is the frequency response (AFC). A loudspeaker is considered to be of high quality if the unevenness of its frequency response does not exceed 10%.
Speaker settings
Most important parameters loudspeakers required for electroacoustic calculation are: sensitivity P 0 , dB, power, P W, W, loudspeaker beamwidth, SDN, deg. Depending on these parameters, it is possible to determine the sound pressure P dB, dB developed by the loudspeaker or its loudness, as:
Knowing the noise level in the protected room USH, dB and the directivity pattern of the used loudspeaker SDN, deg, we can estimate the effective area sounded by the loudspeaker:
Loudspeaker classification
Loudspeakers are classified by application, characteristics, design, protection class, etc. Consider the two most widely used types of loudspeakers, which differ in the way they are converted: electrodynamic and horn.
Electrodynamic loudspeakers
The main working unit of an electrodynamic loudspeaker is a diffuser, which converts mechanical vibrations into acoustic ones. The loudspeaker diffuser is set in motion by a force acting on a coil rigidly attached to it, which is in a radial magnetic field. Coil vibrations are transmitted to the diffuser, which in turn creates acoustic vibrations propagating in the air. Loudspeakers with electrodynamic conversion are widely used in enclosed spaces - bus station buildings, metro lobbies, electric train cars. These speakers usually have high quality sound. A characteristic example of such a loudspeaker is the ROXTON PA-620T ceiling loudspeaker, Fig.3.
Fig.3 - Appearance of the ceiling wide range loudspeaker ROXTON PA-620T
Horn loudspeakers
A horn loudspeaker consists of a horn and a driver. The horn is a matching element between the driver (emitter) and environment. The driver, rigidly connected to the horn, converts the electrical signal into sound energy, which is received and amplified in the horn. Amplification of sound energy inside the horn is carried out due to a special geometric shape that provides a high concentration of sound energy. The use of an additional concentric channel in the design makes it possible to significantly reduce the size of the horn while maintaining its quality characteristics. Horn loudspeakers are actively used in railway, sea and river transport - in any open areas, including railway platforms, as well as metro stations, they are widely used for scoring parking lots, installed on "campaign" cars. Typical examples are horn loudspeakers ROXTON HP-15T (ROXTON HP-30T) or ROXTON HS-30T (ROXTON HS-50T), Fig.4.
Fig.4 - Appearance of horn loudspeakers - plastic ROXTON HP-15/30T (left), aluminum ROXTON HS-30/50T (right)
Fig.5 - ROXTON WP-06T wall-mounted full range loudspeaker
Transformer loudspeakers have undeniable advantages over low-impedance loudspeakers - they are simple in terms of design and installation. The principle of transformer matching allows you to build long lines, which, in combination with parallel connection, allow you to implement multi-zone and distributed warning systems.
The specifics of the design of warning systems in the field of transport
Loud announcements at stations and platforms
Many of you have probably had to deal with a situation where, being at the station or platform, you could not make out or hear an informational announcement. There are several problems here, both organizational and technical. Sounding open areas requires a competent approach that takes into account possible collisions - sound reflection, high noise levels. There are many examples of incorrect sounding of stations and railway platforms. The most common mistake is to exceed the allowable speaker spacing. The reason for this error is the desire to "kill two birds with one stone" - to cope with high level noise by minimal means, for which, as a rule, the number of loudspeakers is reduced, and their power is increased. Yes, it is cheaper this way, but this leads to the appearance of an echo, exceeding the permissible volume, and uneven sounding of the territory.
The emergence of an echo
Figure 6 - Critical speaker spacing
Example. After the reconstruction of the Kazansky railway station in Moscow, an echo effect appeared on the territory of the platforms. Initially, the territory was opened and powerful sound clusters (ROXTON CS-840T sound columns) were installed to sound it. When a roof (reflective coating) appeared, an echo effect appeared with a very noticeable delay of ~ 1s. There are also reverse examples. The platforms of the Moscow railway station in St. Petersburg are sounded correctly. The loudspeakers are placed with the optimal pitch; informational announcements are well heard, the sound on the platforms is pleasant and comfortable.
Exceeding the permissible volume
The first error automatically leads to the second, associated with exceeding the permissible volume level (sound pressure) at the listening point. The sound should not be very loud; this can lead to fear and panic. So, according to existing standards, the sound pressure at the listening point should not exceed 120 dB. This can be expressed as a formula as follows:
where r 1 is the distance from the loudspeaker to the nearest listener.
The value of r 1 was introduced into the formula not by chance. So, for example, the ROXTON HS-50T horn loudspeaker (Fig. 4) has a sound pressure of about 126 dB, which a priori exceeds the critical value. But almost always (to increase the coverage area) powerful horns are installed at a sufficiently high height (r 1).
Example. Above the entrances of Moscow metro stations (metro stations Vykhino, Elektrozavodskaya, etc.), powerful horns were installed at a height of ~ 2.5 m. Minimum distance between the speaker and the listening position is approximately 1m. This arrangement, given that the sound pressure of most horns is greater than 120 dB, is an undoubted error.
Loud-speaking communication in electric trains
To date, the quality of high-profile announcements carried out by drivers of electric trains (railway, metro) leaves much to be desired. Poor quality leads not only to irritation, but also to the loss of necessary information. The reasons. The first and most banal is the moral and physical obsolescence of the equipment used. The second reason is subjective and is related to the incorrect use of technical means. So, for example, improper use of the microphone leads to poor hearing. The reasons for this may be different, for example, not a standardized distance between the speaker and the microphone capsule, Fig. 7.
Fig. 7 - Microphone design on the example of the ITC ESCORT T-621 model
Conversely, if the distance between the speaker and the microphone capsule is small, then audibility may be distorted. Poor sound quality may be due to poor sound path settings, for example, the wrong ratio of microphone input sensitivity and gain. A serious reason that interferes with the good perception of sound information inside the car is various noises, for example, the noise of an oncoming electric train, the noise of people, and the own noise of the electric train. But this noise can increase significantly, for example, due to the penetration of noise from a passing oncoming train into the open windows. Such additional noise worsens the audibility by about 6-10 times (each open window increases the noise level in the car by 1dB).
These factors can be taken into account by a comprehensive (including air conditioning) re-equipment of cars. And there are such examples. Domestic Aeroexpress trains are equipped with higher quality sound system. Speech announcements (including advertising) in cars are preceded by a signal to attract attention, and are carried out in a pleasant female voice. Announcements are well received, as it is almost silent in the insulated and air-conditioned carriages.
Emergency situation
The emergency notification system is a complex of not only technical means designed to transmit emergency information, but also organizational measures aimed at ensuring the safety of people. So, for example, the organization of emergency messages in subway cars leaves much to be desired. During a long stop of an electric train in a subway tunnel, anxiety will certainly increase among passengers (provoking panic). An unexpected, sharp, unintelligible announcement by the driver (that the train will soon move) can be replaced by a competent (pre-recorded) informational announcement of a general plan. In case of a longer stop, you can launch an additional message regarding, for example, the rules of behavior for people in the subway (which is successfully implemented when voicing escalators).
(a. emergency warning alarm signal, breakdown signal, distress signal; n. Alarmschallanlage; f. alarme, signal d "alerte, avertissement d" avarie; i. seсal o aviso de alarma) - a form of emergency informing those working on the bugle. enterprises about the danger and the need to move to special. shelter or exit to the surface. A.o. carried out with the help of special equipment or complex tech. means of communication and signaling. A.o. includes: transmission of information about the danger to subscribers located at the workplace; transmission of orders and instructions to them; receiving messages from subscribers at the control room; implementation of two-way loud-speaking communication of the dispatcher with subscribers. Main species A.o. - emergency loudspeaker. Auxiliary the role of attracting the attention of workers to the transmission of an important message is performed by sound, light or aromatic. signaling. For A.o. at the mines of the CCCP, sets of intrinsically safe equipment (IGAS-3, GIS-1) are produced, consisting of a dispatcher's console (communication control), subscriber devices, loudspeakers, additional. intercoms, etc. As communication lines between dispatching and subscriber devices A. o. special are used. cables or free cores of mine mains and distribute, telephone cables. It is allowed to use A. o. for the transfer of technology. information (subject to extraordinary and independent transmission of information about the accident in any direction).
C. B. Babkov, B. H. Mits.
Watch value emergency alert in other dictionaries
Alert Wed.- 1. The process of action on the value. verb: to notify, notify.
Explanatory Dictionary of Efremova
Alert— alerts, cf. (official). Action on verb. notify - notify.
Explanatory Dictionary of Ushakov
Parameter Alarm Value— See Parameter value alarm
Economic dictionary
Emergency Incident— Emergency
incident on a ship of the navy of the Russian Federation, which resulted in
damage to the ship resulting in loss of seaworthiness and requiring at least 48 hours........
Economic dictionary
Alert- -I; cf.
1. to Notify - notify. O. about the meeting.
2. Message, news. Send someone. with notification.
Explanatory Dictionary of Kuznetsov
Parameter Value Emergency- parameter of a product or product, which alone or together with other parameters characterizes the possibility of occurrence emergency. Z.p.a. applied........
Economic dictionary
Incident Emergency- in marine insurance, an accident refers to an insured event. There are: 1) an accident on a ship, as a result of which there was a loss of seaworthiness ........
Economic dictionary
Agreement, Emergency— In ocean and sea transportation insurance: a document issued by a cargo insurer in order to release cargo held after the occurrence of an insured event, ........
Economic dictionary
It is important not only to say something, but also to be heard. That is why the question of the most appropriate way to provide reliable information about the occurrence of any situations to people in the room (employees, customers, etc.) is now so acutely raised. Communicating with everyone personally or shouting is quite difficult. That is why there was a need for other, more reliable methods. The public address and notification system has become the most acceptable solution this question.
What is loud notification for?
Today, a lot of different high-quality devices are offered to create a speakerphone. Using such a public address system, it is possible in the shortest possible time, in large numbers and at the same time to notify people in the building about a fire or other emergencies. However, in normal mode, loud announcement can also be used to broadcast a wide variety of events, announcements or background music. Nowadays, it is rare to find an organization that does not use some kind of scheme for one-way notification. And there are quite a few reasons for introducing a public address system. Let's consider some of them.
Efficiency of notification
With the help of loudspeakers and notifications, important announcements will be heard simultaneously by all employees and customers who are around. Currently, there is simply no more efficient method of alerting people. In addition, using this method, you can change your messages very quickly, which is quite convenient at construction sites, factories, factories and other industrial facilities. Reliable dispatch communication between specialists and local managers is simply indispensable for any factory.
Selecting an alert object
Thanks to selector communication, the object of obtaining information can be chosen by yourself. Public address systems allow you to independently exclude any premises or territory, so that information is broadcast only in the place where it is necessary. This method is ideal for educational institutions, serious large industrial enterprises, hospitals, etc.
Ease of use
Usually they have an extremely simple and intuitive instrument interface, and therefore it is not only very convenient to use such tools, but also quite easy. After installation and configuration by the masters of all equipment, almost every person will be able to use the speakerphone, without having a specific education.
Horn loudspeakers
This is the best option for the street and large open objects. Such a loud notification is often used in parks, swimming pools, sports fields, factories, and various exhibitions. Due to the excellent speech quality and sound power, the range of the horn is very high. Such loudspeakers are held in most cases on universal mounting brackets and are easy to set up. It is for this reason that the installation and use of devices does not cause practically any problems.
In addition, horn loudspeakers are well protected from various temperature influences, humidity and dust. Due to this, they can be used in almost any type of premises, as well as in open spaces. Street loud notification is installed on the facades of houses, concrete pillars, which significantly increases the list of possible locations for using such a device.
The choice of loudspeakers is quite diverse, which is why you should approach the choice of the device as carefully as possible. In order to competently and profitably order a horn, it is important to choose only trusted suppliers, because very often low-quality devices of absolutely incomprehensible origin are on sale.
speakerphone
Such modern hands-free devices are suitable for gas stations, various registries, cash desks in banks, information desks and many other such establishments. Thanks to good quality speech relay, resistance to temperature and moisture, the use of such devices makes communication between the manager and the client the most convenient and enjoyable. There is no need to raise your voice or listen during the conversation. Moreover, the worker can independently adjust the volume of the speaker, which ensures the comfort of his work.
EMERGENCY NOTIFICATION OF THE PERSONNEL OF MINES AND MINES VIA RADIO CHANNEL
Vasilioglo Anastasia Dmitrievna
5th year student, Department of Electrical Engineering, Power Engineering, Electromechanics, NMSU "Gorny", St. Petersburg
E-mail: collection _ stasia @ mail . en
Ivanov Sergey Leonidovich
scientific supervisor, Dr. tech. sciences, professor,Department of Mechanical Engineering, NMSU "Gorny", St. Petersburg
Semenov Mikhail Alekseevich
scientific supervisor, Ph.D. those. Sciences, Associate Professor,Department of Electrical Engineering, Power Engineering, Electromechanics, NMSU "Gorny", St. Petersburg
One of the main tasks of ensuring labor safety at mining enterprises is timely prompt notification of personnel about the occurrence of an accident. In the safety rules PB 05-618-03 (clause 41), emergency notification is the transmission by a mining dispatcher of messages (code, text, voice) to underground workings individually for each miner, regardless of his location before, during and after the accident. The tasks of monitoring mine personnel are directly related to emergency notification. They are also reflected in clause 41 of PB 05-618-03: search or emergency positioning - detecting a person and determining his location under a blockage through a layer of rock mass at least 20 m thick with an error of no more than 2 m within 2 days after falling under the blockage in case of an accident and rescue operations; observation or technological positioning - determining the position of personnel in underground workings under normal conditions with an accuracy of the mine working area at the time of the accident.
Based on the content of paragraph 41 of PB 05-618-03 presented above, the following requirements can be formulated for the emergency warning system for underground personnel in mines and mines:
1. The notification should cover the entire area of underground mine workings;
2. Alert signals must be received by every miner or engineer located in underground workings, regardless of location;
3. The warning system must remain operational before the accident, during the accident and after the liquidation of the accident;
4. The notification time should be minimal (no more than a few minutes);
5. The amount of information transmitted by the alert should be sufficient for the personnel to understand the nature of the accident and possible ways evacuation.
For the most part, these requirements are met by systems that use a radio channel operating through the rock mass to transmit warning signals. These include: "Earth-3M", "SUBR-1P", "Radius-2", "SUBR-1SVM", "Granch", "Talnakh" and others. The most common of them at mining enterprises, functionally more developed and constantly improving, are the SUBR-1 and Radius-2 systems. Moreover, "Radius-2" meets all five points of the requirements formulated above.
Other underground radio communication systems that have become widespread in mining enterprises in last years, based on a radiating cable and microcellular technologies (DECT, WiFi) have much wider functionality and are able to perform all the functions of an emergency notification, but they do not comply with paragraph 3 of the above requirements. The presence of cables and equipment in underground workings in the event of an accident will lead, first of all, to their failure, and hence to loss of communication with underground personnel.
Warning systems through the rock mass do not have stationary equipment in mine workings. They consist of a transmitter located on the surface of the mining operation and receivers, which are supplied to all underground personnel. Consequently, in the event of an accident, no equipment will be damaged and communication with the dispatcher will remain operational.
How such systems work, let's look at the example of a wireless underground notification complex, paging, surveillance and search for people caught in an accident - "Radius-2". The complex consists (Fig. 1) of the transmitting equipment of the PRD, the antenna-feeder device of the AFU and the receiving devices of the PRM. The transmission equipment includes a remote control remote control Remote control of the mountain dispatcher.
Figure 1. The structure of the complex "Radius - 2"
The transmitting antenna of the complex, which is a grounded dipole or a frame covering a mine field, can be suspended on power line supports, laid on the ground surface in the ground or in mine underground workings that are not dangerous for gas and dust. The antenna is connected to the PRD power amplifier, which, depending on the geometric dimensions of the mine field, the geoelectric properties of rocks, is selected from a range of 1.25; 2.5; 5.0; ten; 15 kW.
The receiving device PRM, which is built into the body of the explosion-proof mine head lamp, provides the following functions: notification of an accident, personal call to workers, regardless of where they are in the mine; search for people caught in the accident in the mine; location monitoring, automatic personnel records of mine personnel.
In the event of a pre-emergency or emergency situation, a mining dispatcher with a remote control transmits coded radio signals of an alert or a paging call to underground workings through the rock mass. The capacity of the codes of the Radius-2 complex is: personal call - 1024, general notification by type of accident -4, transmission of digital or text messages - 16. Transmission is carried out by means of low-frequency electromagnetic waves using a frequency grid from the lower range of 25 Hz to 2500 Hz with step 50 Hz. The frequency grid allows you to select the optimal transmission frequency through the rock mass, depending on their conductivity. The transmitting device programmatically selects the optimum by switching from one frequency to another.
Receivers pick up low-frequency signals and convert them into flashing lamp lamps of various frequencies and durations and in parallel into sound signals. By the type of these signals, miners receive information about ongoing events in the mine - an accident or a call to talk on the phone.
The zone of operation of the Radius-2 complex is up to 2000 m deep through the mountain range, up to 15 km along the strike of the mine field.
To implement the search for people caught in an accident, a miner's radio beacon is built into the receiving device. It is turned on by the dispatcher with the remote control after giving a signal about an accident and starts emitting special signals with a power of up to 10 mW. Based on these signals, during the liquidation of the accident, the rescue service can determine the location of the miner using the radio direction finder "Radius ShRP" through the rock mass at a distance of 5-15 m.
Location monitoring or positioning of personnel was carried out in the Radius-2 complex using the technology of active RFID tags, which are high-frequency transmitters (434.5; 433.3 MHz) built into mine headlights. Receivers (readers) of these signals are installed in certain places of the mine, where it is necessary to control the presence of personnel and are connected to the dispatcher's computer by a fiber-optic communication channel. The reading distance is up to 40 m. In an emergency, when the fiber optic channel is destroyed, the computer will record the position of the personnel at the time of the accident, which will become the starting point for searching for people caught in the accident.
Thus, the "Radius-2" system ensures the fulfillment of all five points of the requirements for emergency warning systems for underground personnel in mines and mines. However, paragraph 5 requires further development and improvement of the system. Indeed, in four code signals about the type of accident, it is difficult to contain information about the nature of the accident, the specific place where it occurred, its development and consequences, and also to outline the fastest way to the surface. In the complexes "SUBR-1P" and "SUBR-1SVM" such development was embodied in the transmission of text messages to individual miner's pagers, which are supplied to engineers and work managers. Text messages are programmed according to the positions of the emergency response plan (up to 508 messages, 40 characters each). In addition, arbitrary text messages can be transmitted, which are received by an individual receiving device and transmitted at a high frequency to the miners' pagers.
Point 5 of the requirements formulated above can be fully implemented only with voice notification. It is known that the frequency band of the voice range is in the range of 300-3500 Hz. The highest frequency of the range (3500 Hz) is 1000 Hz higher than in the operating frequency range of the Radius-2 complex. An increase in the frequency of the transmitted signal increases the risk of its rapid attenuation in the rock mass and, consequently, a decrease in the range (depth) of the voice alert.
At St. Petersburg Mining University, studies were carried out to determine the depth of propagation of an electromagnetic field during the transmission of speech signals through a rock mass. The research results are presented in fig. 2 in the form of graphs characterizing the decrease in the strength of the electromagnetic field (E, μV/m) depending on the depth of its propagation (L, m) in the rock mass at different frequencies of the speech range. Calculations were made for the average integral conductivity of rocks of the rock mass equal to 10 -2 S/m. Such conductivity is characteristic of anthracites, mudstones, siltstones, wet clays, quartz-sulphurous shales and other rocks. It can be seen from the graphs that the strength of the electromagnetic field at the lower frequency (300 Hz) at a depth of 1200 m is about 12 μV/m, which is quite sufficient for satisfactory operation of the receiving devices. At a frequency of 3500 Hz, already at a depth of 500 m, the electromagnetic field strength becomes less than 9 μV / m, which speaks in favor of unstable radio communications.
This leads to the following conclusion: emergency notification in voice format is possible only at depths of less than 500 m, which is unacceptable for modern mines and mines, the depth of which underground workings are 1000 m or more.
Figure 2. Attenuation of the electromagnetic field during the transmission of a speech signal through a rock mass for various frequencies in the range:
1 - at a frequency of 300 Hz; 2 - at a frequency of 1000 Hz; 3 - at a frequency of 3500 Hz.
This conclusion does not mean that speech notification should be abandoned. Ways to increase the depth of transmission should be sought. One of these ways is to correct the amplitude-frequency characteristic of the transmitting path, which is aimed at amplifying in more the high-frequency part of the speech spectrum, as the most attenuated when propagating in a mountain range. Such a decision suggests itself on the basis of an analysis of the characteristics presented in Figs. 2.
If we compare, for example, the electric field strength at frequencies of 300 Hz and 3500 Hz at a transmission depth of 500 m, it turns out that at a frequency of 3500 Hz it has decreased by a factor of 24 compared to a frequency of 300 Hz. This means that in order to increase the transmission range (more than 500 m), it is necessary to compensate for the decrease in high-frequency components. To do this, it is required to increase the gain of the transmitting path for the higher frequencies of the speech range by at least 24 times compared to the gain of the low-frequency components.
This problem can be solved by introducing into the final cascade of the transmitting path a correction chain of series-connected inductance L and capacitance C, connected in series with the transmitter antenna. This circuit should have a predominantly capacitive resistance, so that with an increase in the frequency of the speech signal, its total resistance decreases, and the gain of the cascade increases.
The values of the parameters L and C must be chosen taking into account the occurrence of the resonant frequency fres = 1/2π. The value of fres should be less than all frequencies of the speech spectrum, and even more so, the frequency of 3500 Hz. For these reasons, the product LC should not exceed 2·10 -9 . It is not difficult to implement such a corrective chain.
We have tested the final stage of the transmission path in the form of a low-frequency amplifier based on a bipolar transistor. Its parameters were calculated taking into account the corrective circuit. When testing such a cascade, an increase in the electromagnetic field at frequencies from 300 to 1000 Hz by about 1.5 times was observed, and at frequencies from 1000 to 3500 Hz, its smooth decrease by about 2 times. At the same time, the electromagnetic field strength at a depth of 500 m for the high frequency spectrum was 450 μV/m, which is about 45 times higher than without the corrective chain. This means that the field can extend to depths greater than 500 m.
Further studies have shown that with the selected final stage with a corrective circuit, the electromagnetic field at a frequency of 3500 Hz can reach a depth of 800 m, providing a strength within 15 μV / m, which is quite enough to provide a stable voice announcement.
Bibliography:
1.Babenko A.G. Principles of building multifunctional safety systems for coal mines, experience and prospects for their use in Kuzbass / A.G. Babenko, S.E. Lapin, A.V. Wilhelm, S.M. Orzhehovsky - Labor safety in industry, 2011, No. 1. P. 16-22.
2. Within the radius of increased attention to the miner / Coal of Kuzbass, International Scientific and Practical April - 2011. P. 68-69. magazine, March - April 2011. pp. 68 - 69.
3. Drabkin A.L., Proskuryakov R.M., Semenov M.A. The system of wireless impulse single-sideband transmission of speech signals through a rock mass using repeaters / Izvestiya vuzov "Mining Journal" No. 2, 2002. P. 107-111.
4. "Week of comfort and safety of life" in Kuzbass approved the know-how of the Krasnoyarsk Scientific Research Center "Radius". Izvestia of the region dated November 24, 2011. Special issue.
5.Semenov M.A. Compensation system for the decrease in the electric field in a rock mass // Online Electrician: Power Engineering. New technologies, 2012 - [Electronic resource] - Access mode - URL: http://www.online-electric.ru/articles.php?id=9(Date of access: 05/10/2012).
6. Ferkho V.A., Vesnin V.N. Issues of equipping with technical means of emergency notification and determining the location of personnel in underground mine workings of mines and coal mines. Mining Journal of Kazakhstan, 2010, No. 8, pp. 47-50.
(a. emergency warning alarm signal, breakdown signal, distress signal; n. Alarmshallanlage; f. alarme, signal d "alerte, avertissement d" avarie; and. seсal o aviso de alarma) - a form of emergency information for those working on the bugle. enterprises about the danger and the need to move to special. shelter or exit to the surface. A.o. carried out with the help of special equipment or complex tech. means of communication and signaling. A.o. includes: transmission of information about the danger to subscribers located at the workplace; transmission of orders and instructions to them; receiving messages from subscribers at the control room; implementation of two-way loud-speaking communication of the dispatcher with subscribers. Main species A.o. - emergency loudspeaker. Auxiliary the role of attracting the attention of workers to the transmission of an important message is performed by sound, light or aromatic. signaling. For A.o. at the mines of the CCCP, sets of intrinsically safe equipment (IGAS-3, GIS-1) are produced, consisting of a dispatcher's console (communication control), subscriber devices, loudspeakers, additional. intercoms, etc. As communication lines between dispatching and subscriber devices A. o. special are used. cables or free cores of mine trunk and distribution, telephone cables. It is allowed to use A. o. for the transfer of technology. information (subject to extraordinary and independent transmission of information about the accident in any direction). C. B. Babkov, B. H. Mits.
- - bringing signals to the authorities, troops and the population: about the danger of an air attack, radioactive, chemical, biological contamination, about natural disasters etc....
Dictionary of military terms
- - bringing to the authorities and troops in a short time the established signals, orders and information of the military command about the actions of the enemy and friendly troops ...
- - bringing to the bodies of day-to-day management, forces and means of the RSChS and the population of warning signals and relevant information about emergencies through the warning system ...
Civil protection. Conceptual and terminological dictionary
- - bringing to the authorities and troops in a short time the established signals, orders and information of the command ...
- - informing the population about the dangers arising from the conduct of hostilities or as a result of these actions, one of the main tasks in the field of civil defense ...
Emergency Glossary
- - bringing to the authorities, troops, naval forces and the population signals about the danger of an air attack, radioactive, chemical and biological contamination, natural disasters and ...
Marine vocabulary
- - "..." emergency alert" - notification of search and rescue services about aircraft in distress;..." Source: Decree of the Government of the Russian Federation of 11.03 ...
Official terminology
- - ".....
Official terminology
- - Etc. about...
Spelling Dictionary of the Russian Language
- - NOTIFY, -I'm eating, -I'm eating; - still; owls, whom about what. The same as notifying. O. employees about the meeting...
Explanatory dictionary of Ozhegov
- - NOTIFICATION, alerts, cf. . Action under ch. notify-notify...
Explanatory Dictionary of Ushakov
- - notification cf. 1. the process of action according to Ch. notify, notify 2. The result of such an action...
Explanatory Dictionary of Efremova
- - ...
Spelling Dictionary
- - notify...
Russian spelling dictionary
- - ...
Word forms
- - Cm....
Synonym dictionary
"Emergency Alert" in books
Early warning
From the book The Forgotten Side of Change. How creativity changes reality author Brabander Luc DeEarly Warning In the spring of 1883, sailors sailing between the islands of Java and Sumatra noticed strangely smooth, rolling waves that they had not seen before. They looked at a nearby uninhabited volcanic island and saw that above
Psychic Alert
From the book Theosophical Archives (compilation) author Blavatskaya Elena PetrovnaPsychic Alert Translation - K. Leonov “Can any of the numerous readers of The Theosophist enlighten me as to the influence exerted on me in the case which will be discussed below? I, of course, categorically deny that it was some kind of spiritual
5.4 EMERGENCY RESCUE
From the book Rockets and People. hot days cold war author Chertok Boris Evseevich5.4 EMERGENCY RESCUE On December 10, Mishin held a meeting of the Council of Chiefs, at which they considered the modified Soyuz LCI program and the draft schedule for the manufacture of 7K-L1 spacecraft for circling the Moon. The first manned lunar flight was proposed in June 1967. Prior to this in
Caller Position Announcements
From the author's bookCaller Position Announcements Alert settings for callers waiting in the queue.
Death notice and condolences
From the book The Complete Modern Encyclopedia of Etiquette author Yuzhin Vladimir IvanovichDeath notification and condolences If a family member dies, all relatives, friends and good acquaintances are immediately informed by telegram, telephone call or in writing. The recipient of the notice must, if possible, personally take part in
Fire warning
From the book Universal Handbook foreman. Modern construction in Russia from A to Z author Kazakov Yury NikolaevichWarning people about a fire In each house (residential block) with a height of 3 floors, autonomous smoke fire detectors (hereinafter referred to as detectors) must be installed that meet the requirements of NPB 66 and are placed in accordance with special requirements. Assignment for
Twitter Presentation Alert
From the book Proshow Producer Version 4.5 Manual by Corporation PhotodexNotifying presentations on Twitter ProShow has built-in support for notifying you on Twitter about your new presentations. This option is available every time you upload a presentation to any public media website. When the upload is complete, a window will appear
Crash
From the book System Programming in the Windows Environment author Hart Johnson MAbort Any termination of program execution for reasons other than reaching the end of a try block and falling through or executing a __leave statement is considered an abort. The result of executing the __leave statement is to jump to the end of the __try block and
From the book Federal Constitutional Law "On the Constitutional Court Russian Federation" author Russian LegislationArticle 51. Distribution of materials. Notification of the meeting Notification of the meeting of the Constitutional Court of the Russian Federation, copies of appeals and received responses to them, copies of the audited acts, and, if necessary, other documents are sent to the judges and participants
38. Don't forget about PR, organizational details and notification of participants
From the book 50 tips for non-material motivation author Ivanova Svetlana Vladimirovna38. Do not forget about PR, organizational details and notification of the participants "Whatever you call a yacht, so it will sail." The result of a competent PR is a great first impression, and as they say, you will not get a second chance to make a first impression. It's very important to do it right -
Emergency lighting
From the book Rules for the installation of electrical installations in questions and answers [A guide for studying and preparing for a knowledge test] author Krasnik Valentin ViktorovichEmergency lighting Question. What types of emergency lighting are divided into? Answer. It is divided into safety lighting (designed to continue working in case of emergency shutdown of working lighting) and evacuation (6.1.21). Question. What are the requirements for
Chapter III Trajectories, control, navigation, radio communications, emergency return
author Shuneiko Ivan IvanovichChapter III Trajectories, control, navigation, radio communication, emergency
Emergency return from deep space. Emergency return during the phase of entering the flight path to the Moon
From the book Manned Flights to the Moon author Shuneiko Ivan IvanovichEmergency return from deep space. Emergency return during the phase of entering the flight path to the Moon
Emergency return on the active section of the exit to the ISL trajectory
From the book Manned Flights to the Moon author Shuneiko Ivan IvanovichEmergency return on the active phase of entering the ASL trajectory If the LRE of the service compartment failed at the beginning of the active phase of entering the orbit of the ASL, the return of the command compartment to the antipode point can be carried out by three methods. Method I. If the LRE of the service compartment
Emergency return from ISL orbit
From the book Manned Flights to the Moon author Shuneiko Ivan IvanovichEmergency reentry from AIS orbit If it is necessary to perform an emergency return from a holding orbit around the Moon, insertion into the Earth flight path is made earlier than planned and the return trajectory is aimed at the landing point in the middle of the Pacific Ocean.
Loading...