Feedback from fire alarm zones.

It is no secret that modern Russian fire safety regulations have many gaps, contradictions and omissions.

Unfortunately.

One example of this is the so-called «feedback».

The term seems to be on everyone's lips, but what exactly is meant by it is a mystery shrouded in darkness.

At one time, the editorial board of the «Algorithm of Safety» magazine asked the head of VNIIPO a question about what should be understood by «feedback».

Both the question and the answer were published in No. 1 for 2004.

Later, six months later, practically the same answer, word for word, was included in the letter of the Main Directorate of the State Fire Service of the Ministry of Emergency Situations of Russia on clarifications on the application of fire safety standards NPB 10403.

In fairness, it should be noted that this very brief information, contained in one small paragraph, remains the only attempt known to us by government agencies to somehow explain their position on “feedback”.

And this, perhaps, in more than 20 years…

We tried to analyze the chronology of any mentions of “feedback” in official documents available to the general public. What we got can be seen in the table.

From the chronology of these documents and their more detailed analysis, one can make an unambiguous conclusion that there is a paradoxical situation — Russian fire safety regulations require that «feedback» be mandatory in type 4 and 5 warning systems, but do not say a word about what exactly it should be.

It is impossible to find clear and understandable requirements for «feedback» in the current official regulations.

In broad strokes, we can outline the range of pressing issues that plague people who are forced, by the nature of their work, to deal with «feedback»:

What are the specific and clearly defined goals and purposes of «feedback» —
Who, besides the dispatcher, is a user of «feedback» —
What technical means should be used to ensure the «feedback» function —
What standards and rules should be followed when planning and placing technical means of «feedback» inside a building —
What are the requirements for communication lines?
Should they be fire-resistant (FR) cables or not?
For how long should the backup power supply for the «feedback» be provided?
For what ambient noise conditions should the «feedback» be designed?
Should automatic functions for monitoring the status of the technical means of the «feedback» be implemented?

And these are only the most general, practical questions that lie on the surface, the answers to which are not yet provided by domestic standards.

As the saying goes, water does not flow under a lying stone, and we tried to analyze the requirements for similar systems abroad.

Considering the fairly frequent statements recently made by officials and voiced in many media outlets that Russia is following the path of harmonization with European standards, we decided to focus on the British standard BS 58399.

It contains a lot of structured and useful information on such systems. We will try to give a brief overview of this standard in this article.

INTRODUCTION TO BS 5839-9

Further, for convenience and brevity of presentation, we will use the term used in the standard – EVC, an abbreviation for the phrase Emergency Voice Communication.

The standard does not establish requirements for equipping buildings with EVC systems; it only provides explanations on how these systems should be designed, installed, and maintained. It clearly defines the goals and purposes of EVC systems.

In particular, it directly states that EVC systems allow firefighters and other persons to interact with each other in emergency situations (hereinafter referred to as ES).

In addition, EVC systems allow communication with physically disabled people (disabled persons) who find themselves in emergency situations and are unable to evacuate on their own.

The standard specifies that the EVC system includes:

subscriber stations (subscriber intercoms);
at least one master station (dispatcher console);
power supplies;
wired communication, power and control lines.

The EVC system does not replace the existing fire alarm system in the building, but is an independent set of technical means designed to solve specific and characteristic problems of providing two-way voice communication to people in emergency situations.

It is necessary that the EVC system allows calls to be made (communication to be initiated) by both subscribers and the dispatcher.

Communication between them must be two-way. The EVC system must not introduce any delays in the transmission of signals and data.

The conversation must be as clear as possible, as if there were no electronic means of communication at all.

The standard requires that the EVC system should not have any portable or movable components. Therefore, for example, it is not allowed to use portable radio stations and mobile phones as subscriber stations.

This is how the British standard differs from the regulations of a number of other countries, in particular the USA, where in some cases portable handsets are allowed to be used in such systems.

THE SIGNIFICANCE OF EVC SYSTEMS

The functions of EVC systems can be divided into basic and additional. The BS 5839-9 standard defines only basic functions and does not regulate additional ones. The following can be considered as basic functions:

used by the building administration at the initial stage of evacuation.

Before the arrival of the fire service, EVC systems can be used for communication between the dispatcher and the personnel inside the building responsible for evacuation.

Typically, the call will originate from a subscriber station on a specific floor of the building to notify the dispatcher that the evacuation of people from that floor has been completed;

— is used by firefighters during the evacuation process.

Once firefighters have arrived at the building, they will typically take control of the evacuation process.

One firefighter will be stationed in the control room and will communicate with other firefighters via the EVC system;

— is used by firefighters after the evacuation has been completed. Firefighters will continue to use the EVC system after the evacuation has been completed to assist in extinguishing the fire;

— is used by people with disabilities. These are people who cannot evacuate on their own, have taken refuge in safety zones and are waiting for help.

They must be able to identify their location and be able to contact personnel, such as a dispatcher or other person responsible for the evacuation. For this purpose, specially equipped safety zones must have subscriber stations that allow two-way communication.

The standard also provides examples of additional functions of EVC systems:

— is used by a limited number of personnel for non-emergency purposes. For example, a security officer patrolling a protected area uses an EVC system to communicate with the control room;

— is used in speakerphone mode. The subscriber station may have a built-in loudspeaker. This feature will allow the dispatcher to continue transmitting signals to a person in distress who is near the subscriber station;

— is used to monitor the sound environment. The dispatcher can monitor the surrounding sound environment around the subscriber station.

This feature will allow the dispatcher to continue hearing signals from a person in distress who is near the subscriber station; used in conference mode.

BS 5839-9 does not recommend the use of subscriber stations for direct communication with each other. However, it is permissible for subscribers to communicate with each other in a «conference» mode, which is organized by the dispatcher.

SUBSCRIBER STATIONS

Subscriber stations are located at strategic points within the building.

Most often, several subscriber stations are allocated, specially located so that they can be used by firefighters during the evacuation of people from the building or during fire extinguishing.

BS 5839-9 provides for two types of subscriber stations:

— Type A – subscriber stations with a handset. Conversation with the dispatcher occurs through a handset. The dispatcher is called automatically when the handset is picked up. The call is hung up in the same way if the handset is hung up.

— Type B – subscriber stations without a handset. Conversation with the dispatcher occurs through a microphone and loudspeaker built into the station body. The subscriber calls the dispatcher by pressing a special button, and he answers the call from the dispatcher in the same way.

Subscriber stations of both types must be provided with brief instructions on how to call the dispatcher.

It is preferable that these instructions be made in the form of graphic icons.

If the subscriber stations will be used by firefighters or personnel ensuring the evacuation of the building, then Type A stations should be used. Type A subscriber stations may also be used to provide communication to people with disabilities.

Type B subscriber stations are similar to call stations in intercom systems. Type B stations are used to provide communication to people with disabilities.

If the subscribers may be temporary residents of the building (for example, visitors to a shopping center), then Type B stations should be used.

A significant limitation for them is their low protection from ambient noise. Accordingly, the standard recommends that the ambient noise level should not exceed 40 dBA. Therefore, these devices should be installed in areas where there are no powerful noise sources in the form of sound and speech notification, or special acoustic «hoods» should be installed.

When an incoming call is received at the subscriber station, an audible signal should be turned on. In Type A devices, it should automatically stop after the handset is picked up or the door is opened.

In Type B devices, the ringing tone shall stop after the answer button is pressed. When an incoming call is received, the red indicator light on the subscriber station shall turn on, it may be constantly lit or flashing.

Both the microphone and the loudspeaker or earphone of the subscriber station shall have a frequency response of at least +/- 3 dB in the frequency band 250 Hz — 4 kHz, and the microphone in Type B devices shall have the same value in the frequency band 250 Hz — 5 kHz. The upper frequency limit of 4 kHz allows for an audio transmission bandwidth of 3.4 kHz, which is traditionally used in telephone communications.

This general rule is acceptable for devices with a handset, when the distance between the earphone and the subscriber's ear and the distance between the subscriber's mouth and the microphone are small enough to reduce the impact of ambient noise on the quality of communication.

In devices without a handset, a wider bandwidth is required to combat the effect of ambient noise. The amplifier stages of the subscriber station must provide a total audio signal transmission bandwidth of at least 300 Hz — 3.4 kHz.

The subscriber station is powered by the master station.

Design requirements

— The handset in type A subscriber stations must be placed inside a housing closed by a door or a removable front panel.

— All components of the subscriber station must be strong and reliable.

— In places where subscriber stations protruding from the wall surface may interfere with people or cause harm to them (for example, on evacuation routes), flush-mounted subscriber stations must be used so that they are flush with the wall surface.

— If subscriber stations are placed outdoors, they must be all-weather designed and have a housing with a protection rating of at least IP65. The protection rating of the housing of subscriber stations that are placed indoors must be at least IP3X.

— The housing or front panel of a subscriber station intended for evacuation and firefighters must be red or have explanatory inscriptions in red.

— The subscriber station shall, as a rule, be readily accessible for use at all times. If the subscriber station is located in a readily accessible public place and may be subject to vandalism or malicious interference, it shall be protected in such a way that it can be reliably opened and used in an emergency.

— If, in the event of a fire, the door of a subscriber station is automatically opened or retracted by a signal from the fire alarm system, then it shall not automatically close or lock during the reset of the fire alarm system. In addition, such subscriber stations shall also have built-in means for manual opening.

—If key-locked locks are used to protect access to subscriber stations, then all subscriber stations must have one common key. Each responsible person must have his own personal copy of the key.

— Subscriber stations at sports facilities must be lockable to prevent their malicious use. In this case, authorized personnel of the sports facility must always have access keys and be trained to use subscriber stations in emergency situations.

— A subscriber station located in a safety zone (in a shelter for people with disabilities) must be easily accessible for use at all times and must not be locked.

Placement requirements

Preferred locations depend greatly on the intended use of the subscriber stations. Stations intended for use by people with reduced mobility should be placed in designated safety areas.

Station stations intended for evacuation and fire extinguishing purposes should be placed where they can be used by firefighters and emergency evacuation personnel (e.g. in lobbies, hallways and on fire escapes).

— The height at which subscriber stations are installed should be appropriate to their intended use.

— The stations should be located in places where satisfactory communication quality can be ensured, i.e. in places that are least exposed to ambient sound noise.

— The number and locations of subscriber stations should be agreed upon with all interested parties (the designer, the building administration, the fire department, the labor protection service), and in some cases with the police.

— The number and locations of subscriber stations should be determined at the initial stage of designing the EVC system when defining its goals and objectives.

— At sports facilities (stadiums) and similar structures, subscriber stations should be located so that the distance to the nearest station is no more than 30 m.

— If the EVC system inside a building is used for use by firefighters when extinguishing a fire, subscriber stations should be located on all floors of the building that are served by fire escapes, and in the fire hall of each fire escape.

— If the EVC system inside a building is used to control evacuation, subscriber stations should be placed on all evacuation stairs on each floor of the building.

— Each subscriber station should be placed in a protected hall or in a protected corridor adjacent to the stairs. If such a hall or corridor is not available, then the subscriber station should be located inside the protected stairwell.

— In multi-story buildings, to assist in locating subscriber stations, subscriber stations should normally be installed in the same location on each floor.

— Since the subscriber station will be located inside the building along an escape route, which should by definition be free of obstructions and barriers, the subscriber station should normally be mounted on a wall. Typically, the subscriber station should be located at a height of 1.3 — 1.4 m in an easily accessible, well-lit, visible location free of obstructions.

— Subscriber stations inside a building should, as far as possible, be placed in places with the lowest possible noise level (recommended no more than 40 dBA). If the noise level is higher, its impact can be reduced to an acceptable level by installing «acoustic hoods» or «acoustic barriers».

— Subscriber stations in public buildings should, as far as possible, not be placed in places where they may be subject to vandalism and malicious acts.

— If the EVC system is intended to provide emergency communications to people with reduced mobility, subscriber stations shall be placed in each safety zone where such people can take refuge and await further assistance and, if possible, in the immediate vicinity of the evacuation lift on each floor of the building. These stations shall be placed at a height of 0.9 — 1.2 m in an easily accessible, well-lit and visible place free from obstructions.

MASTER STATIONS

The EVC system must have at least one master station, from which the entire system will be monitored and controlled.

The master station must be located in the control room, at the central fire post, at the central security post or in another similar room and must be designed for continuous use in emergency situations.

In the event of a fire, control of the master station may be transferred to a representative of the fire service. In large buildings or building complexes, there may be several locations from which the evacuation process is monitored and controlled.

Then it may be advisable to install master stations in each of these rooms.

In this case, one of the master stations must be able to become the «main» one, in order to seize control of the entire system for an indefinite period of time.

The master station must be able to receive calls from subscriber stations.

If required, the master station shall have the ability to call each subscriber
station, a group of subscriber stations, or all subscriber stations.

At a minimum, the master station shall have a handset or microphone and loudspeaker, controls for calling and receiving calls from subscriber stations, incoming call indicators, a status indicator, and a general fault indicator.

The controls on the master station must be designed for use in emergency situations. Therefore, the use of the master station must be simple and understandable, and the controls and indicators must be clearly marked.

Controls

— There must be «accept call» buttons that allow you to answer a call from each subscriber station individually. This function may be performed using other means, such as on the display and keyboard.
— If the EVC system requires that there be means to call subscriber stations, then additional controls must be provided on the master station:
— make call buttons — allow the master station to make a call to any of the subscriber stations. This function can be performed by other means, for example, on the display and keypad;
— all call button — allows the master station to make a simultaneous call to all subscriber stations;
— Optional «group call» buttons — allow the master station to make a simultaneous call to a specific group of subscriber stations.
— It is permissible to combine each of the «accept call» and «call» buttons.
— There must be means that allow switching to a conversation mode with selected subscriber stations. It is permissible for these means to be integrated into the «call», «all call» and «group call» buttons.
— It shall be possible to interrupt a conversation. For example, an ongoing call to a certain subscriber station may be interrupted by making a subsequent call to another subscriber station. However, this function shall not affect the status indicators of the subscriber stations.
— It shall be possible to test the indicators. When this function is started, all indicator lights and the audible signaling device shall be switched on at the master station.
— If a speakerphone mode is required, then a «loudspeak» button shall be provided to enable this mode.
— If an ambient sound control mode is required, then a «listen» button shall be provided to enable this mode.
— If software is used to control the master station, then a tamper-proof means of resetting the software or hardware shall be provided.
— It shall be possible to switch off the audible fault signal. At the same time, the state of the visual fault signals shall be maintained. The audible signal shall be automatically resumed after 8 hours if the fault is not eliminated. The audible signal shall also be resumed automatically in the event of new faults.
— If other controls are provided at the master station that are not related to the primary purposes of the EVC system, these controls must be clearly separated from the primary ones and must be blocked when the EVC system is used for its intended purpose.

INDICATORS

— Indicators at the master station are required to display incoming and outgoing calls, display EVC system faults, confirm the system is operational and the availability of certain additional functions.
— Each of the «call», «general call» and «group call» buttons shall be provided with an indicator. It shall change to a red flashing mode if the corresponding outgoing call has been made. After the called subscriber station has picked up the handset, the indicator's glow mode shall change to green. After the master station has interrupted (completed) the call, the indicator shall return to a red flashing mode and remain in this state until the subscriber station has hung up.
— Each of the «accept call» buttons must be equipped with a separate LED indicator. It must switch to a red flashing mode if an incoming call is received from a subscriber station. After the «accept call» button is pressed on the master station, the indicator light mode must change to green. After the master station interrupts (completes) the call, the indicator must return to the red flashing mode and remain in this state until the subscriber station hangs up.
— There shall be an audible signaling device for incoming calls. The audible signal for incoming calls shall be clearly distinguishable from other audible signals, such as a fault signal.
— If a hands-free mode is provided, the «hands-free» button shall be provided with a green indicator.
— If a sound environment monitoring mode is provided, the «listen» button shall be provided with a green indicator.
— There shall be a permanently lit green power indicator. It shall only go out in the event of a general power failure.
— The master station shall have fault indicators. They shall be yellow or amber in colour.

— It is permissible for all indications to be given not on separate LED indicators, but on a text or graphic display. The only exception is the incoming call indicator, which must be a separate indicator. Fault detection. Automatic detection of any of the following faults shall be provided:
— Short circuit or disconnection of any primary power source of the EVC system equipment, or disconnection of the primary power supply from such source.
— Short circuit or disconnection of any backup power source of the EVC system equipment, including those where backup power is provided by backup batteries.
— Disconnection of any backup battery or short circuit within a battery.
— Short circuit or disconnection of any device charging the backup batteries of the EVC system.
— Blown fuse or operated circuit breaker, isolator or protective device that could interrupt voice communications in an emergency.
— Malfunction of the subscriber intercom, including any open or short circuit in the connecting circuits (including the circuit to the microphone capsule, the circuit to the loudspeaker or telephone earphone) and any malfunction of the associated amplifier.
— An open or short circuit in the wiring between the subscriber intercom and the master station.
— A short to ground in the wiring between the subscriber intercom and the master station if it affects the main functions of the EVC system.
— Failure of any processor to correctly execute its program, including the termination of any scanning or polling process or the process of detecting any errors in memory check procedures.
— Failure of any component of the master station that makes emergency communications impossible (including the circuit to the microphone capsule, the circuit to the loudspeaker or telephone earpiece).

In the event of EVC system malfunctions, the following indications shall be given at the master stations no later than 100 seconds after the malfunction has occurred:
— Audible signal.
— Visual signal on a separate general malfunction indicator light.
— Visual signals on individual indicator lights and/or on the alphanumeric display:
— failure of power supplies;
— malfunction of communication lines;
— failure of any subscriber station;
— in the case of using radial line topology – failure of any of the cables connecting the subscriber station to the master station.

Placement requirements:

As a rule, the master station should be placed in a secure area — to prevent unauthorized access or malicious use.
Another advantage of this type of placement is that the room is likely to have a low level of constant noise, and the master station can be placed
on a table.
— The master station should be placed in close proximity to the fire alarm control panel or near the fire alarm system display devices.
— It is preferable to place the master station in a room with permanent presence of personnel or in a guarded room.
— Where it is not possible to locate the master station in a separate room and it has to be located in a freely accessible area, it should be located as close as possible to the firefighters' access point into the building. In this case, the master station should be mounted on a wall and may also need to be in a lockable enclosure. However, the master station should not be located on escape routes if possible, so that the operator is not exposed to the flow of evacuating people.
— If the operator is to stand while working with the master station, it should be installed so that the center of its control field is at a height of 1.4 — 1.5 m from the floor.
— The master station should be located in an area where the probability of a fire is low.
— The Master Station should be located, as far as possible, in places with the lowest possible noise level (recommended no more than 40 dBA). If the noise level is higher, its impact can be reduced to an acceptable level by installing «acoustic hoods» or «acoustic barriers».

ELECTRICAL SUPPLY

The main power supply for the EVC system is usually supplied from the low-voltage power supply network of the building, which must be reliable and capable of providing the maximum load connected to it in normal and emergency modes.

In order to minimize potential failures, the EVC system feeder network should be designed to be unaffected by failures and malfunctions of other equipment, as well as by power outages in the building for maintenance or energy conservation purposes.

During the life cycle of the EVC system, it is likely that the feeder network will occasionally fail, such as when the building power is interrupted or when the final circuits feeding the EVC system fail.

Accordingly, there must be backup power sources. Typically, these are automatically recharging batteries that can provide the EVC system with power while the main power grid is being repaired.

Backup sources must be reliable; switching between power sources must not affect the operability of the EVC system.

The duration of the backup power supply must be longer than the maximum expected duration of the power outage at the building input.

A power failure may occur due to a failure of the end sections of the network that supply power to the EVC system.

In the event of any failure of the normal power supply, the capacity of the backup batteries must be sufficient to enable the EVC system to be used in an emergency for a reasonable period of time. If the building has an automatically starting backup generator, the capacity of the backup batteries can be reduced, provided that this generator supplies power to the EVC system.

Requirements for the electrical network.

These requirements apply to the electrical network that serves the EVC system.

It should be considered as an integral part of the EVC system, even if it is not implemented by the EVC system installer.
— For electrical safety reasons, the main power supply to all parts of the EVC system must be supplied via a protective tripping device (e.g. a circuit breaker) from the main tripping device of the building.
— The network wiring must be dedicated exclusively to the EVC system and must not supply any other system or other equipment. The wiring must start from a point on the building power supply system that is close to the main tripping device of the building.
— Double-pole tripping devices must be installed in the immediate vicinity of the equipment supplied by the EVC system.
— The number of tripping devices between the main power input to the building and between the power source of the EVC system must be the minimum necessary.
— Each tripping device and protective device that can disconnect power from the EVC system, with the exception of the main tripping device of the building, must be provided with one of the following inscriptions:
– “EMERGENCY VOICE COMMUNICATION SYSTEM” – a protective device that serves only the EVC system, but does not have a built-in manual switch (disconnector).
– “EMERGENCY VOICE COMMUNICATION SYSTEM. DO NOT SWITCH OFF” means a manual switch (whether or not it has a protective device) that serves the power circuit of the EVC System.
– “WARNING. THIS SWITCH DISCONNECTS POWER TO THE EMERGENCY VOICE COMMUNICATION SYSTEM” means any manual switch that disconnects power from both the EVC System and other circuits.
— Each isolator, switch or protective device that is capable of disconnecting the main power to the EVC System shall be installed and protected so that it cannot be accessed by unauthorized persons.
— The supply circuits of the EVC system shall not be protected by residual current devices (RCDs), unless otherwise specified in other standards. If an RCD is required for electrical safety purposes, then the occurrence of a fault in any other circuit or equipment shall not result in the disconnection of the main supply from the EVC system.
— The electrical network shall be capable of providing the maximum load of the EVC system used, regardless of the state of any backup batteries (e.g. disconnected or completely discharged), for example when the master station is transmitting signals to all subscriber stations simultaneously.

Power Supply Requirements

These requirements apply to each power supply that is part of the EVC system:

— Switching power between the main and backup sources shall not result in any disruption to voice communications.
— A failure of the primary power supply shall not affect the backup power supply, and vice versa. The operation of a single protective device shall not result in the failure of both the primary and backup power supplies.
— The normal power supply mode shall be indicated by a green indicator, which shall be illuminated if the power supply is in good condition.
The indicator shall be located so that it is easily visible to the personnel responsible for monitoring faults in the EVC system (e.g. an indicator at each master
station).
— Each power source, primary and backup, must be capable of providing the maximum load of the system, regardless of the state of the other source.
— The backup power source must include a rechargeable backup battery and an automatic charger.
— The backup battery must be designed for a service life of at least 4 years under operating conditions that correspond to its use in the EVC system. Car batteries should not be used for this purpose.
— Each battery must be labeled with the date the battery was installed. The label must be located so that it can be read without removing the battery.
— The following are the requirements for all backup batteries:
— If the building does not have an automatic backup generator that supplies power to the EVC system, the backup batteries must be sized to support the system in a standby state for at least 24 hours and then in a talk state for at least 3 hours.
— If the building has an automatic backup generator that supplies power to the EVC system, the backup batteries must be sized to support the system in a standby state for at least 3 hours and then in a talk state for at least 3 hours.

WIRING

The components of most EVC systems are interconnected by copper cables.

Sometimes connections are made by other means, such as fibre optics. Where fibre optics are used, they must provide equivalent durability and reliability to other types of cable.

It is essential that all connections are ready to function correctly at the start of a fire and for as long as possible.

This is necessary to ensure that voice communications continue to function during evacuation and for as long as possible while the fire is being extinguished.

Therefore, cables used to connect the components of the EVC system must be fire-resistant for a long time.

Also, one of the most important issues is the operability of the electrical network that supplies the EVC system.

Even if the system has a backup power source, its reliability may not be as high as that of a conventional electrical network.

Accordingly, the cables of the power supply network must also be inherently fire-resistant.

The standards define two levels of cable fire protection – standard and extended. Cables used in the EVC system must have an extended level.

An exception may be cables used in sports facilities and laid underground, but they must have increased mechanical protection.

Usually, copper cables with a mineral sheath have the required level of mechanical protection and at the same time extended fire resistance.

The probability of failure of any part of the EVC system, which occurs due to mechanical damage to the cable, can be reduced by the following measures: use cables with increased mechanical strength; carefully select cable routing routes; provide mechanical protection for the cable in those places where it is most likely to be damaged.

Wiring monitoring does not guarantee that a cable will not fail. But monitoring is essential to minimise the time between the occurrence of a cable fault and its identification and, therefore, repair. Wiring monitoring and mechanical protection of the cable are additional measures, but not alternatives.

It is the designer's responsibility to ensure that the cables used in the EVC system are suitable in terms of their electrical characteristics, including current carrying capacity and voltage drop.

Care must be taken when selecting the cable type and routing to avoid electromagnetic interference from other cables and electromagnetic sources. This is especially true for systems where cables are used to transmit serial data.

In the latter case, the cables selected must also support the required data transfer rate.

EVC system circuits must be separated from other circuit wiring to reduce the likelihood of EVC system failure and to reduce possible negative impact on the EVC system, such as the following events:

— cable insulation failure in other circuits;
— fire caused by a fault in another circuit;
— electromagnetic interference caused by the close installation of another circuit;
— damage caused during installation or dismantling of other circuits in trays, cable channels and cable ducts in which EVC system circuits are installed.

The use of cables in accordance with the standards and in combination with the correct methods of their separation and connection are sufficient measures to separate EVC circuits from other circuits and to ensure that the EVC circuits remain operational in the event of damage to the insulation of other cables or fires in other cables.

The cables of the EVC system must be highlighted in a certain color or marked in a certain way, for example with tags, so that it is possible to identify the separation of EVC circuits from other circuits.

In this case, there will also be less chance of accidental manual intervention in the circuits of EVC systems, for example, when performing any work in the circuits of other systems.

BS 5839-9 provides the following practical recommendations for the installation of EVC wiring:
— The electrical characteristics of all cables (voltage drop, current carrying capacity, impedance) must be suitable for the EVC system.
— All cables in the EVC system, including dedicated EVC mains cables, must be fire resistant, with the exception of underground cables in stadiums and similar venues.
— Cable fastening methods must be such that the cable can remain operational in the event of a fire. For example, plastic clips, plastic ties and plastic cable channels must not be used.
— Splices in cables should be avoided whenever possible. The method of making connections in cables should be such as to minimize the likelihood of failure in the early stages of a fire. Connecting contacts should be made of materials capable of operating at high temperatures (except for connectors installed inside EVC equipment). All cable connections should be made inside junction boxes, each box should be marked «Emergency Voice Communication System».
— Except in particularly severe conditions, copper cables with a mineral sheath or copper cables reinforced with twisted-wire armour may be used.
— All conductors must have a cross-sectional area of at least 1.0 sq. mm, with the exception of cables with twisted or stranded pairs. The latter must have a cross-sectional area of conductors of at least 0.5 sq. mm.
— EVC system cables must be separated from cables, pipes or cable channels of other systems, including other security systems, such as a fire alarm system.
— If multi-wire cables are used to connect between components of an EVC system, they must not be used to connect other systems. This standard does not preclude the use of multiplexing of signals from other systems.
— Low voltage EVC cables should be separated from extra-low voltage EVC cables. In particular, the mains supply cable should not be introduced into equipment through the same cable entry as an extra-low voltage cable. Separation of low voltage and extra-low voltage circuits should also be maintained within EVC equipment.
— Wherever possible, all EVC cables should be of the same colour, which should be different from the colour of cables used in other electrical systems in the building.

We would like to separately mention some recommendations of BS 5839-9 that EVC installers should follow when laying cables:

— Surface mounted cables must be laid neatly and securely and fixed at appropriate intervals in accordance with the cable manufacturer's recommendations. Cables must not be laid across suspended ceilings.
— If a new pipe, tray or trunking is being installed, sufficient clearance and the necessary installation accessories must be provided for the cable to be laid.
— If the cable passes through the external wall of the building, it must be laid in a smooth pipe made of metal or other non-hygroscopic material embedded in the wall. To prevent the penetration of water, dust and vermin, the pipe must be installed with a slope towards the outside of the wall and sealed with a lightweight waterproof compound.
— If the cable passes through the internal wall of the building, a small shaped opening must be provided. If additional mechanical protection is required, a smooth-bore bushing should be embedded in the wall.
— Care must be taken to ensure that the ends of any bushings do not have sharp burrs that could damage the cable when it is laid.
— If the cable is laid through a ceiling, the bushing must protrude above the floor by at least 300 mm.
— Through openings in the building structure through which cables, pipes, trays or cable channels pass must be as small as possible. They must be carefully sealed with fire-resistant materials in order to maintain the specified fire resistance rating of this structure. There must be no empty space around the cable, pipe, tray or cable channel through which fire or smoke can penetrate.

CONCLUSIONS

In modern Russian reality, quite a lot of objects can «fall» under the equipment of warning and evacuation control systems of the 4th and 5th types. Here are just some of the objects listed in [2], to which these requirements apply:
— schools more than 3 stories high or with a capacity of more than 1,600 people;

— hotels, hostels, dormitory buildings of sanatoriums, boarding houses and rest homes more than 9 storeys high;
— theaters, concert halls, libraries, circuses, stadiums with more than 1,500 visitors;
— museums and exhibition halls with more than 1,000 visitors;
— shopping malls where the area of the fire compartment floor is more than 3,500 sq. m or the height is 5 storeys;
— sports halls with more than 500 visitors;
— railway stations more than 1 storey high;
— universities with a height of more than 9 floors.

And all these objects must have «feedback», which today is a big «blank spot», because there are no criteria that allow us to evaluate whether «feedback» has been implemented correctly or not at a particular object.

And it will not be any other way until clear and logical standards for «feedback» appear in Russia.

Standards that will be able to dot all the i's and cross all the t's and the provisions of which will be clearly understood by all interested parties: the population, the state, business.

Even a brief acquaintance with the British standard BS 5839-9 allows you to see that in the UK, as in many other countries, the standards and rules affecting the safety of life and health of people are developed and observed extremely carefully.

They exist and work for the benefit of people.

The standards are developed in such a way as not to omit ambiguity and polysemy in the interpretation of their provisions.

They reflect even the smallest and, as it may seem to someone, insignificant issues. But, as we know, nothing is more important than trifles, especially in matters of safety…

LISTING LIST:

1. Federal Law of July 22, 2008 No. 123-FZ. Technical Regulations «On Fire Safety Requirements».

2. SP 3.13130.2009. Fire Warning and Evacuation Management System.

3. GOST R 53325-2009 Fire-fighting equipment. Technical means of fire-fighting automation. General technical requirements. Test methods.

4. GOST 1947288 National automated telephone communication system. Terms and definitions.

5. GOST 715385 General-purpose telephone apparatus. General specifications.

6. NPB 10495. Design of fire warning systems for people in buildings and structures.

7. NPB 10403. Fire Warning and Evacuation Management Systems for People in Case of Fires in Buildings and Structures (Design of Fire Warning Systems for People in Cases of Fires in Buildings and Structures).

8. Letter of the Main Directorate of the State Fire Service of the Ministry of Emergency Situations of Russia No. 18/4/2098 dated 28.07.2004 «On Clarification of the Requirements of NPB 10403».

9. NPB 7798 Technical Means of Fire Warning and Evacuation Management. General Technical Requirements. Test Methods.

10. RND 734589 Interim Guidelines for Design of Fire Warning and Evacuation Management Systems for People in Case of Fires at National Economy Facilities.

11. Design of Fire Warning and Evacuation Management Systems for People in Case of Fires in Public Buildings. Guide to SNiP 2. 08. 0289.

12. BS 58399:2003 Fire detection and fire alarm systems for buildings – Part 9: Code of practice for the design, installation, commissioning and maintenance of emergency voice communication systems

13. Magazine «Algorithm of security». 2004. – 1. ALGORITHM 21

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D. Yakunkin, Technical Director of the company «StatusSvyaz»

Magazine «Algorithm of security» No. 5, 2011

Feedback from fire alarm zones.