Loop (security and fire alarm). Radial alarm systems - application features and development prospects Operating principle of a fire alarm loop

V.N. Korenev,
Ph.D., Head of Development
and implementation of Security Systems LLC,
Novosibirsk city

Threshold signaling loops, despite their low information content and susceptibility to interference, continue to be used in various systems alarm system. This is due to the fact that there are still many non-addressable detectors and sensors on the alarm product market that have two stable states at their output, corresponding to normal and alarm. They successfully compete with addressable products due to their low cost and compatibility with various control and control devices.

Despite the simplicity of the circuitry, threshold alarm loops can be made much more informative than is implemented in existing equipment. This becomes possible with the use of modern microprocessor technology, which increases the ADC bit capacity, data processing performance, and the amount of built-in memory, and at the same time reduces the price.

However, an increase in information content is associated with an increase in controlled events and the complexity of algorithms for transition from one state to another. It is becoming increasingly difficult to describe these processes. Therefore, when developing such products and describing them for users, it is convenient to use physical and software models of the alarm loop.

Each threshold alarm loop (AL) of the device can be described by models from two points of view:

From a physical point of view– this is an electrical circuit connecting the device with detectors (sensors) through wire connections (Fig. 1). Each AL has various circuit design options selected by the developer. The connection diagram shows the detector contacts, resistors and other components that ensure the operation of the alarm loop.

Any detector can be represented as an electrical contact, which, when triggered, abruptly changes its resistance: it becomes either closed (contact resistance is zero) or open (contact resistance is infinity).

The detector contacts are connected by wire connecting lines to the terminals of the control panel.

In the control panel, the terminals are connected to a “Resistance Meter”, which measures electrical resistance the entire AL circuit, and the “Decision Device”, based on the value of its resistance, makes a decision about whether the detector has worked or not.

Fig.1. Threshold alarm loop model

The AL is connected to the resistance meter through the terminals located on the board of the control panel (RCD). The meter measures the electrical resistance of the entire AL circuit, and the deciding device, based on the value of its resistance, decides whether the detector has worked or not.

From an information point of view is a software object consisting of a fixed set of events. An event in the loop can occur as a result of a change in the loop resistance, or come from outside, in the form of control commands. The set of events is determined SHS tactics. Each SHS tactic includes:

Type of alarm loop (fire, security, emergency and control) and name;
Electrical connection diagram;
Scale of AL resistance ranges, divided by thresholds;
Linking states to AL resistance ranges;
List of AL events;
Matrix of events.

As an example of the use of terms, consider the “Single-threshold” fire alarm loop tactics. This tactic provides for the issuance of a “Fire” signal when any one or more detectors are triggered:

Alarm loop type – fireman, single-threshold .
Electrical circuit diagram - can be performed in several versions (Fig. 1.1.):

with normally closed contacts of detectors (K1, K2). In this case, the contacts are connected in a loop line in series, and the control resistors are connected in parallel with the contacts of the detectors;
with normally open contacts of the detector (K3, K4). In this case, the contacts of the detectors are connected in parallel to the loop line, and the control resistors are connected in series with the contacts;

Fig.2. Electrical circuits switching on fire detector contacts.

3) Resistance range scale, divided by the developer by resistance thresholds into 8 ranges: D1 ... D8 (Fig. 3).

Fig.3. ShS resistance range scale

When the contacts of the detectors are closed and opened in various combinations, the resistance of the loop falls into one or another range.

Linking states to AL resistance ranges

Loop states are understood as physical or logical properties that characterize a loop when its resistance changes.

In the “Single-threshold” ShPS, the developer assigned the following states:

Norm;
Fire;
Break.

These states are assigned to ranges:

List of AL Events

An event is a transition from one state to another. In this case, both the states of the loop itself and other states of the device related to the loop are taken into account.

In the “Single-threshold” ShPS, the developer has assigned the following events:

Reset- an event in the device at the time of its reboot (power on);
Not ready- an event meaning that after a reboot the loop resistance is not in the “Normal” range;
On duty– the resistance of the loop has moved into the “Normal” range [D5];
Fire– loop resistance in any of the “Fire” ranges [D2] [D3] [D4] [D6] [D7];
Closure- loop resistance is in the “short circuit” range [D1];
Break- loop resistance is in the “Open” range [D8];

Event Matrix

The event matrix determines the sequence of events when states change. Using a matrix it is convenient to represent the loop operation algorithms. The matrix is a table that contains the following elements:

Fig.4. Appearance event matrices.

The principle of using the matrix to describe the loop operation algorithm is presented in Fig. 5. As an example, in the far left column, let’s select the current status as “On Duty”. Let's highlight the line with events in the field of events that are possible while in this status with a green background. Next, let’s consider what event will happen when a new “Fire” loop state appears:

Fig.5. An example of how the matrix works when the “Fire” condition occurs

As a result of the matrix’s operation, the plume switched to a new current status of “Fire”. Analysis of the influence of new loop states in the “Fire” status shows that no other physical change in the loop resistance will change this status. In order to remove a loop from the “Fire” status, it must be transferred to a new “Reset” state. This state can come to the loop from the outside: for example, when the reset button is pressed.

Thus, the matrix representation significantly facilitates the description of complex algorithms for the operation of threshold alarm loops and can be used both in their development and in describing the operation of the product in the user manual. Obviously, the matrix representation is also convenient when describing the algorithms of other components of alarm products.

Literature:

Pinaev A., Nikolsky M. Assessment of the quality and reliability of non-addressable devices fire alarm//Journal "Security Algorithm", No. 6, 2007.
Neplohov I.G. Analysis of the parameters of a two-threshold PPKP loop // Safety Algorithms No. 5, 2010.
Device for monitoring dangerous situations and warning "Khranitel-IT"//

New technologies, energy-saving components, ability software perform certain actions and other innovations in last years changed not only the manufacturing technology of fire detectors, but also the methods of their installation and installation. This, in turn, caused changes in existing standards and regulations for the design of fire alarm systems. For example, the radial stub topology, which has long been used and was considered traditional until recently, is now increasingly being replaced by a ring topology. Possibility of installation large quantity fire detectors in one loop without reducing their reliability and performance makes the use of ring loops quite attractive compared to radial ones. Modern ring loops are multifunctional and allow, in addition to connecting automatic and manual fire detectors, to control additional equipment using various I/O modules.

Advantages of using analog ring loops:

Fig.1. Radial loops Fig.2. Ring train

Maximum information content of the loop, achieved by using intelligent fire detectors and their full addressing;
High reliability of the ring loop, compared to the radial one - in the event of a break or short circuit, the radial loop partially or completely fails; in the ring loop, devices called insulators automatically cut off the damaged area, and the loop continues to function as two radial branches. If the loop breaks, the insulators are not activated;
Possibility to create radial branches if necessary for optimization cable diagram;
Less labor costs and consumption of cable materials with the same number of detectors.

Esserbus - maximum reliability, minimum costs
ESSER fire control panels support esserbus and esserbus-PLus ring loops. The esserbus ring loop is a two-wire loop with the following features:

Maximum cable length 3500 m;
Up to 127 devices per loop;
Up to 127 groups of detectors per loop;
Up to 63 radial branches (up to 32 devices per branch) per loop;
Up to 32 transponders per loop (up to 100 transponders per control panel);
The voltage in the loop is 27.5 V.

In addition to the features of the esserbus technologies described above, there is the esserbus-PLus ring loop with improved characteristics. The new cable supports automatic detectors IQ8Quad series with built-in alarm devices, IQ8Alarm series addressable alarm devices and IQ8Wireless wireless devices. To connect all these devices, no additional wiring is required, i.e. Data transmission, signals and power supply for all loop devices are carried out over just two wires. The esserbus-PLus loop is supported only by the IQ8Control series control panels.

Alarm loop (AL) is one of the components object system security and fire alarm system. This is a wire line that electrically connects the remote element (elements), the output circuits of security, fire and security-fire detectors with the output of control panels. A fire alarm loop is an electrical circuit designed to transmit alarm and service messages from detectors to the control panel, as well as (if necessary) to supply power to the detector. The AL usually consists of two wires and includes remote (auxiliary) elements installed at the end of the electrical circuit. These elements are called load or terminating resistor.

Let's consider a two-wire alarm loop. As an example, Figure 2.4 shows a combined fire alarm with a load Rn at the end.

Rice. 2.4 Combined fire alarm loop with load Rn at the end

In addition to the load resistance, there are a number of factors that create additional load in the AL circuit - this is the equivalent resistance of the AL wires themselves, the “leakage” resistance between the AL wires and between each loop conductor and the “ground”. The permissible limit values of these parameters during operation are indicated in the technical documentation for a specific device. The AL input is connected to the elements of the control panel.

AL is one of the most “vulnerable” elements of an on-site fire and security alarm system. It is exposed to various external factors. The main reason for the unstable operation of the system is the violation of the loop. During operation, a failure may occur in the form of a break or short circuit of the loop, as well as spontaneous deterioration of its parameters. It is possible to deliberately interfere with the electrical circuit of the loop in order to disrupt its proper functioning (sabotage). At the connection points of the AL, its fastening and laying, current “leakages” may form between the wires and conductors to the “ground”. The leakage resistance is greatly influenced by the presence of moisture. For example, in rooms with high humidity, the resistance between the wires reaches several kOhms.

Let's consider the most common AL methods:

With a description of the direct current loop, used as a remote element by a resistor;

With AL power supply with alternating pulse voltage and used as a load by series connected resistors and a semiconductor diode;

With AL power supply with pulsating voltage and used as a remote element - a capacitor.

The control method with DC power supply involves continuous monitoring of the input resistance of the alarm loop. Figure 2.5 shows a diagram of a typical control unit of a control panel. In the AL control unit, the input resistance is determined by the amplitude value analog signal Uk, removed from the divider arm, which is formed by an AL with an input resistance Rin and a measuring element - a resistor - R and:

U = U p R in / (R in + R and)

Rice. 2.5. Diagram of a typical control unit of a control panel.

The output of the analog-to-digital converter (ADC) is set to

Two voltage thresholds corresponding to the upper and lower limits of the zone of permitted values of the AL input voltage. During operation and changes in the resistance of the loop and the “leakage” resistance, the input resistance of the loop should not go beyond the permissible values. Because exact value threshold can be set only with a certain error determined by the technological spread R and the error of the ADC, then in this case under valid value This implies upper and lower threshold zones. When R reaches the upper (which corresponds to a break in the alarm loop) or lower threshold (which corresponds to a short circuit of the alarm loop conductors), the device must switch to alarm mode. The optimally selected value is considered to be the value of the remote resistor (load resistance), which ensures monitoring of the alarm loop with the specified parameters and generation of an “Alarm” notification when the detector installed in this alarm loop is triggered.

Let's figure out what an alarm loop (AL) is and how to organize it correctly. Let's start with the fact that a security loop is connecting line(electric circuit) combining various alarm sensors (DS) or detectors - in the context of this article these are synonyms.

In addition, the loop contains a terminal device (OU), which coordinates it with control panel(PKP).

The terminal device can be:

resistors;
capacitors;
diodes.

What exactly is installed at the end of the loop depends on specific model PKP. It is worth noting that in systems burglar alarm resistors are most often used, so we will focus on this option. Structural scheme The loop is shown in Figure 1.

I immediately drew all possible types of sensors, we will now consider their operation, but in a real situation, as a rule, one connection option and detectors with the same tactics for generating an alarm notification are used.

Combinations of different connections are also possible, but they are quite rare. Now let's move on to consider the main types of loops and the principle of their operation.

Attention! The numbering of loop types in this article is arbitrary. Moreover, each manufacturer can put its own interpretation into the concept of AL type. Be sure to keep this in mind!

TYPES OF SIGNALING LINES

1. AL with sensors that operate “to open.”

A very common option in security alarms. When the detector is triggered, the electrical circuit is broken and the current in the loop drops to zero. The same thing will happen if there is no power to the detector. But if the sensor malfunctions, there are two options:

the contacts will open;
will remain closed even if an intruder is detected.

In the first case, everything is clear and simple - the device will work and the malfunction will thus make itself known. The second option is dangerous because it can only be detected by fully checking the functionality of the sensor, which no one does every day. The only consolation is that such cases are rare, but, nevertheless, they do happen.

2. AL with a sensor that operates on “short circuit”.

The only difference from the first option is in the connection diagram and in the fact that when triggered, the loop is closed. It is rarely used in security alarms, at least I have not encountered this method.

3. Using a detector with loop power.

Although not often, such sensors are used. If in the first two cases the voltage is supplied via a separate line, then here the detector operates from the voltage supplied to the alarm loop by the control panel. In this case, the alarm signal is generated by an increase in DC current consumption, which is monitored by the control panel.

In this case, the number of connected sensors can be limited to a few pieces. Specific value for their various types should be indicated in the passport of the security device (as well as the possibility of using this option).

4. Addressable alarm loop.

If so far we have considered cases where current monitoring of the AL was carried out, then when using addressable detectors, information about their state is transmitted to digital form. Accordingly, the information content of the alarm system increases. The DS can diagnose its condition and transmit it to the control panel.

PARAMETERS AND FAULTS

Since the security alarm loop is an electrical circuit, it is characterized by the following electrical parameters like current, voltage and resistance. Moreover, the first two are secondary, and the performance of the AL depends on the resistance, which determines its three main states:

"norm";
"break";
"closure".

The normal resistance of the loop should, as a rule, not exceed 1 kOhm, without taking into account the size of the terminal resistor.

It is worth explaining a little the principle of operation of the PKP-ShS-OU combination.

The device supplies voltage to the loop because in good condition the circuit is closed in it appears electricity. Its value characterizes the state of the AL. Normal current limits are set by the terminal device. Deviation in one direction or another triggers an alarm.

The resistance of the loop itself, and this also includes the resistance of the transition contacts in the sensors, determines the maximum permissible deviations. If there is a short circuit in all or part of the loop (one of the faults), the current consumption increases, and a break causes it to disappear. This is the essence of current control.

Thus, there is another critical parameter - the leakage resistance between the wires of the loop, since it is a two-wire line, or “ground”, and one of the conductors. This characteristic is indicated in the control panel passport, but it would be better if its value is about 1 mOhm. Although many devices operate with leaks of several tens of kOhms.

In conclusion, one question that sometimes comes up: what is maximum length security alarm loop? The answer is any at which the electrical parameters discussed above are ensured.

* * *

The site materials are for informational purposes only and cannot be used as guidelines or official documents.

A.V. Rodionov
Deputy Head of the Systems Engineering Department of NVP "Bolid"

Many articles have been written about the fact that radial systems are increasingly being replaced by modern addressable analog systems, which have potentially greater reliability, functionality and information content. Of course, this is true, but radial systems do not stand still!

What are radial alarm systems? Let us define right away that within the framework of this article, by “radial” we mean traditional wired alarm systems, the basis of which is the alarm loop.

Radial signaling systems also have another name - beam. This is due to the fact that each loop forms a kind of beam or radius emanating from the center, which is the control panel.

Advantages of radial signaling systems

The use of modern digital signal processing algorithms in receiving and control devices can significantly increase the reliability of signal detection from detectors and, as a result, reduce the likelihood of false alarms. If we talk about the reliability of the detectors themselves, the indicators are almost the same for both modern threshold and addressable detectors, the elemental base of which and the methods for detecting alarm/fire factors largely coincide. Radial signaling systems have the right to further successful existence according to the following (far from complete) number of indicators:

versatility: any detectors work with any alarm control panel;
the possibility of implementing security and fire zones on one control panel;
low criticality to the parameters of the wired line of the loop;
acceptable reliability indicators;
widespread;
applicability for most types of objects;
wide range domestic producers;
low cost.

It is worth noting that radial systems are not always the best way suitable for certain types of objects. For large facilities where it is necessary to install and maintain several thousand fire detectors, addressable analogue systems are more suitable, since the total costs per detector will be less than in radial systems, and the number of detectors will be smaller. However, for small and medium-sized objects the cost technical means protection, as well as the costs of their installation and maintenance will be lower. In addition, for security alarm purposes, contact detectors are traditionally used, which are ideally suited for radial control panels.

But the main indicator, of course, remains the market demand for wired radial fire alarm systems: according to expert assessments, the share of such systems accounts for up to 70% of the domestic market.

A little history

One of the first alarm systems to appear in our country was created on the basis of a telephone post in the State Hermitage. It was a burglar alarm that used previously installed telephone lines. Until the 1990s Most of the control panels were used as equipment that combined the functions of security and fire alarms, while the tactics for working with both security and fire detectors were the same. The introduction of new standards required the manufacturers of PPCP to separate these functions. The accumulated experience in the development and operation of domestic devices proved the possibility of combining security and fire functions on one device, and computing tools that were sufficiently developed at that time made it possible to realize this unique opportunity without contradictions in terms of the requirements of the standards for security and fire alarms. In the fact that this phenomenon, unique in world practice, has become a reality, a huge role belongs to the Okhrana Research Center, which at that time was part of the VNIIPO. At the same time, foreign addressable, addressable-analog and radio-channel OPS systems began to appear on the market, but the economic crisis of 1998 acutely highlighted the need to develop their domestic functional analogues. Over the past years, developers have worked intensively to solve this problem, and now a number of domestic manufacturers produce their own systems, which are not inferior in quality or functions to foreign ones.

Radial systems also developed: fire control panels learned to determine the number of triggered detectors in a loop (single-threshold and double-threshold fire loops), a verification procedure was introduced for the one triggered from the broadcaster; For security control panels, such functions as protection against sabotage (substitution of a detector), control of opening the detector body, control of a disarmed alarm system, automatic arming of the alarm system, etc. have become available.

Features of use

Let's consider some features of using wired radial fire alarm systems.

Security loops

The tactics of operation of security loops are quite simple: the loop can be either normal (protected), or in alarm, or disarmed. Any violation (transition beyond the normal range) of the armed loop automatically puts it into alarm mode. Most security detectors operate by breaking the loop during an alarm, but what if an attacker decides to block the transmission of an alarm message by jumping the external wires of the loop connected to the detector? To protect against this type of sabotage, modern receiving and control devices monitor a sharp change in the resistance of the loop, even by a small value. If you install a hidden resistor of a small value inside the detector body, the device will detect an abrupt change in resistance in the loop at the moment the jumper is connected and go into alarm mode. At the same time, if the resistance of the loop changes smoothly, for example, in the case of a change in leakage between the AL wires or the wire and the ground, the device should not interpret these changes as an attempt at sabotage. In Fig. Figure 1 conventionally shows circuits and diagrams of loop resistance in both cases.

However, what if the attacker turned out to be more cunning and installed a jumper inside the detector body, at the alarm contact terminals? And in this case, you can find a way out! If the detector has a case opening sensor (tamper), the device will record the fact that the detector case has been opened, which, of course, should attract the attention of the security service. And finding and eliminating the jumper is already a trivial task for the engineering service. Circuits and loop resistance diagrams for this case are shown in Fig. 2.

Of course, the task of protecting against possible sabotage is not solved only by these methods, but when reasonable approach The considered features of the implementation of a security alarm will prevent material losses and significantly save time and effort when searching for potential points of attack by an attacker.

Fire plumes

The operating tactics of fire lines are significantly different from those of security lines. For fire alarms, the main thing is a reasonable compromise between two tasks:

do not issue a false fire report;
respond to the presence of fire factors. The function of determining fire factors and transmitting an alarm message is performed by fire detectors, and the control panel must be able to reliably detect this notification and make a decision on how to respond to it in order to avoid possible losses both from the fire itself and from the consequences of the operation of the means. fire automatics.

What features of the implementation of fire trails can be useful in this case?

The ability to automatically reset the fire detector to return it to its original state after activation. This feature is extremely important for implementing the verification function (request) of a detector triggered in a loop. Detectors are not perfect and may generate false fire alarms. To make sure that the notification is not false, the device resets the detector and waits for it to trigger again. Only after repeated activation is a decision made about the presence of a fire hazard in the protected area.
Possibility of detecting several triggered detectors in one loop. As is known, the equipment of the fire alarm system, when at least two fire detectors are triggered, must generate control commands automatic installations fire extinguishing, or smoke removal, or fire warning, or control of engineering equipment of objects. For loops that can distinguish between the activation of one, two or more detectors, a special designation has been introduced: two-threshold. The use of two-threshold loops allows you to save on the number of detectors installed in one room (three detectors in one loop, instead of four in two loops for single-threshold AL), and also save on wires. In Fig. Figure 3 shows diagrams and diagrams of two-threshold fire alarm systems.
Implementation of mechanisms that minimize the influence of transient processes in loops. Internal circuits Most detectors can be represented in the form of an equivalent RC circuit, which allows one to evaluate the processes occurring in a loaded loop. The more detectors included in a loop, the higher its equivalent capacity. The higher the loop capacity, the more time completion of transition processes.

In what cases do transient processes occur in loops and what can they affect? It is necessary to take into account transient processes primarily in loops with alternating voltage. Each time the polarity is changed, charge/discharge cycles of the internal capacitance of the detector occur, and the voltage in the loop does not “equalize” immediately. As a rule, control and control devices maintain a certain pause before starting to measure the voltage in the loop after changing the polarity. The duration of such a pause must obviously be greater than the duration of the transition process and, as a rule, is hundreds of milliseconds (200-300 ms). But this time may not be enough if there are too many detectors in the loop! In this case, the duration of the transition process is longer than the pause allotted for its completion, and the measurement results are distorted. This effect is also inherent in loops with constant voltage: in the event of a power supply voltage drop in the loop or in the event of a break in the terminal element of the loaded loop. Distortion of the measurement results of the plume parameters under the influence of the transition period may cause the formation of a false fire signal. This must be taken into account when calculating the number of detectors included in one loop. Voltage diagrams in alarm loops during transient processes are shown in Fig. 4. How to minimize the influence of transient processes if the calculation maximum quantity detectors in a loop is determined only by the maximum load current of the loop, and the nonlinear characteristics of the detectors are not given? This problem must be solved by the receiving and control device itself, actually calculating the derivative of the process of changing the state of the loop. This may somewhat delay the response time when the detector is triggered, but it reliably protects against false alarms.

Development prospects

As already noted, it is premature to write off traditional radial signaling systems. Among the promising tasks is further expansion of the functionality of such systems in terms of integration with engineering systems of objects. Development of the so-called technological alarm system based on hardware existing systems security-

fire alarm is justified by the fact that most of engineering equipment (pumps, valves, gate valves, etc.) has contact outputs that are ideal for inclusion in radial alarm loops. In addition, work is constantly underway to improve the reliability of wired radial systems. Here we can distinguish three components, each of which contributes to the overall reliability indicator:

detector;
wired loop as a communication channel;
receiving and control device.

Evolution of radial system segments

Looking back about 10 years, we will see what development path detectors have gone through and what great job was done. While the external design of the detectors has changed slightly, the internal content has evolved quite significantly. The use of microcontrollers has made it possible to use mathematical methods processing signals from primary converters responding to fire or alarm factors. This allows you to filter out random or induced noise, adjust the threshold level of the alarm factor if necessary, and accumulate data on its changes over time. Developed self-diagnosis functions of smoke fire detectors now make it possible to detect a malfunction of the optical channel or a malfunction of the detector’s own circuit, preventing the formation of false fire signals. Further improvement in the reliability of detectors, multifactor detection of alarm/fire, and the use of new methods and algorithms of operation determine the ways of their development. Following the development of detectors, control and monitoring devices have also gone through a similar path of development. But the most “underdeveloped” segment of radial systems remains the loop itself, as a communication channel between detectors and a control panel. Nowadays, having a two-wire line for transmitting a binary state is an unaffordable luxury. In the long term, when the cost of an addressable analogue detector approaches the cost of a traditional threshold detector, radial systems will give up their leading positions, but in the short term, while the cost of addressable systems is quite high, there is no broad alternative to radial systems. But this statement does not mean that radial systems will not develop.

Hybrid systems

There are already hybrid systems on the market that combine the advantages of targeted and threshold systems. In such hybrid systems, called polling address-threshold systems, the following advantages of address systems are realized:

positioning of the fire/intrusion location accurate to the location of the detector;
performance check and automatic identification of each faulty detector;
indication of need Maintenance detector;
possibility of loop branching;
no need to break the cable when removing the detector from the socket.

The prospect for the development of radial systems, in the author’s opinion, lies in the combination of conventional threshold loops and polling address-threshold alarm loops within one device. The cost of one addressable threshold detector will probably be comparable to the cost of two traditional threshold detectors, but for small and medium-sized objects their use will reduce the cost of the system as a whole. If there is a serviceability monitoring function, it is allowed to install one detector in a room instead of two conventional threshold ones.

So, at the end of the article we can draw the following conclusions:

for small and medium-sized objects, radial OPS systems are the most effective in terms of costs, reliability and functionality rational decision;
the use of mechanisms to protect against sabotage of security zones potentially reduces the risk of material losses;
verification of the state of fire detectors, as well as taking into account the influence of transient processes in fire loops can minimize the number of false fire signals;
the use of two-threshold fire plumes allows optimizing costs for materials and equipment;
promising direction development of radial OPS systems: interrogation address-threshold systems.