History of medieval shields (23 photos). Portable signals Square shield

3.2. Portable signals include:

rectangular shields are red on both sides or red on one side and white on the other,

square shields yellow (reverse side green),

lanterns on poles with red fire,

red flags on poles.

3.3. Portable signals meet the following requirements:

a red rectangular shield (or a red flag on a pole) during the day and red fire lantern on a pole at night - “Stop! It is forbidden to pass the signal” (Fig. 3.3,a);

yellow square shield day and night (Fig. 3.3, b) when a dangerous place is located:

• on the stretch - “Driving at a reduced speed is allowed, there is a dangerous place ahead that requires stopping or proceeding at a reduced speed”;

  on the main track of the station - “Driving at a reduced speed is allowed, there is a dangerous place ahead that requires proceeding at a reduced speed”;

  on other station tracks - "It is allowed to transmit the signal at the speed indicated in the warning, and in the absence of it - at a speed of no more than 25 km/h."

Reverse side of the square shield (green) day and night (Fig. 3.3, c) on the stretch and on the main track of the station indicates that the driver has the right to increase the speed to the set speed after passing the dangerous place with the entire train.

Fencing obstacles to train traffic and work areas on haul tracks

3.4. Any obstacle to the movement of trains on the stretch must be protected by stop signals, regardless of whether a train is expected or not.

Work areas on the stretch that require stopping trains are fenced in the same way as obstacles.

Obstacles on the stretch are fenced off on both sides at a distance of 50 m from the boundaries of the fenced area with portable red signals. From these signals at a distance B indicated in column 4 of the table. 3.1, depending on the guide descent and the maximum permissible speed of trains, three firecrackers are placed on the stretch and portable speed reduction signals are installed at a distance of 200 m from the first firecracker closest to the work site, in the direction from the work site.

Schemes for fencing obstacles and work sites on a single-track section are shown in Fig. 3.4a, on one of the tracks of a double-track section - in Fig. 3.4, b, on both tracks of the double-track section - in Fig. 3.4, c.

Portable speed reduction signals and firecrackers must be guarded by signalmen standing with hand-held red signals 20 m from the first firecracker towards the work site. Portable red signals must be under the supervision of the work manager.

When carrying out work with a deployed front (more than 200 m), the work sites are fenced in the order indicated in Fig. 3.4, g.

Portable red signals installed at a distance of 50 m from the boundaries of the area requiring fencing must be guarded by signalmen standing near them with hand-held red signals.

If the place of an obstacle or work on a stretch is located near the station and it is impossible to fence this place in the established manner, then from the side of the stage it is fenced as indicated above, and from the station side a portable red signal is installed on the axis of the track opposite the input signal (or signal sign " Station boundary") with the placement of three firecrackers, guarded by a signalman (Fig. 3.5).

If the location of the obstacle or work is located at a distance of less than 60 m from the input signal (or the “Station Boundary” signal sign), then firecrackers are not placed on the station side. The diagram of the obstacle fencing in front of the input signal is shown in Fig. 3.5.

Fig.3.5

When a train approaches a portable yellow signal, the driver must sound one long whistle of the locomotive (multi-unit train), and when approaching a signalman with a manual red signal, give a stop signal and take measures to immediately stop the train in order to stop without passing the portable red signal.

To distinguish themselves from other railway workers, signalmen must wear a yellow hat with a top.

Places of obstacles to the movement of trains and places of work on multi-track sections are fenced in accordance with the procedure established by the Ministry of Railways.

3.5. If an obstacle suddenly appears and there are no necessary portable signals, you should immediately install a stop signal at the site of the obstacle (Fig. 3.6): during the day - a red flag, at night - a lantern with a red light and on both sides at a distance B indicated in column 4 of the table. 3.1, depending on the guide descent and the maximum permissible speed of trains on the stretch, place three firecrackers.

Fig.3.6

Firecrackers must be guarded by railway employees, who are required to stand with hand red signals at a distance of 20 m from the first firecracker towards the location of the obstacle.

Signals are installed first on the side of the expected train. On single-track sections, if it is not known from which side the train is expected, signals are installed primarily on the side of the descent to the fenced area, and on the site - on the side of the curve or notch.

The detailed procedure for the actions of workers when fencing suddenly arisen obstacles is determined by the relevant instructions of the Ministry of Railways.

3.6. Places through which trains can only pass with a conductor (at a speed of less than 15 km/h), as well as interweaving tracks on double-track sections at the same level, are fenced off as a place of obstacles to movement, but without laying firecrackers. Written warnings are issued about the installation of these signals on trains.

If it is necessary to let a train pass with a conductor for which a warning has not been issued, laying firecrackers is mandatory.

If the passage of trains with a conductor is established for a long time, then portable red signals can be replaced with cover traffic lights, left in the closed position, with warning traffic lights installed in front of them (Fig. 3.7).

Fig.3.7

The installation of these cover traffic lights is announced by order of the head of the railway, and in this case warnings are not issued to trains.

When the fenced area of ​​the track posts is opened on both sides, the movement of trains between these posts is carried out using one of the used means of signaling and communication without a conductor. At the same time, in some cases, a conductor may be appointed to monitor the movement of a train through a fenced area at a set speed.

3.7. In all cases, firecrackers are placed in the amount of three pieces: two on the right rail of the track along the train and one on the left (see Fig. 3.6). The distance between firecrackers should be 20 m.

3.8. Portable speed reduction signals and signal signs “Start of a dangerous place” and “End of a dangerous place” are installed according to the diagrams shown in Fig. 3.2.

If the place requiring a reduction in speed on the stretch is located near the station and it is impossible to fence it in the established order, then from the side of the stage it is fenced as indicated above, and from the station - in the order indicated in Fig. 3.8.

Fig.3.8

When approaching a portable yellow signal, the driver is obliged to blow one long whistle of the locomotive (multi-unit train) and drive the train so as to proceed through the place fenced off by the portable signal signs “Start of a dangerous place (Fig. 3.9, a) and “End of a dangerous place” (Fig. 3.9, b), at the speed indicated in the warning, and in the absence of a warning - at a speed of no more than 25 km/h.

The signal sign "End of dangerous place" is placed on back side"Beginning of a Dangerous Place" sign.

Portable speed reduction signals and signal signs “Start of a dangerous place” and “End of a dangerous place” on station tracks and multi-track sections can be used with shortened poles.

3.9. Places of work on the track that do not require fencing with stop or speed reduction signals, but require warning of workers about the approach of a train, are fenced with portable signal signs “C” for blowing a whistle, which are installed near the track where the work is being carried out, as well as at each adjacent main track (Fig. 3.10).

Portable signal signs "C" are installed in the same order at adjacent main tracks and during work performed, fenced by stop signals (see Fig. 3.4, b and 3.5) or speed reduction signals.

On sections where trains operate at speeds of more than 120 km/h, portable signal signs “C” are installed at a distance of 800-1500 m from the boundaries of the work area.

33. A yellow disc (Fig. 68) gives a signal - movement is allowed with a decrease in speed and readiness to proceed through a dangerous place, fenced with signal signs “Start of a dangerous place” and “End of a dangerous place” (Fig. 95, 96), at the speed set owner of infrastructure or owner of non-public railway tracks.

A green disk (Fig. 69) means the train has passed a dangerous place. On single-track sections, the driver sees such a signal on the left side in the direction of travel.

Places established by the owner of infrastructure or the owner of non-public railway tracks and requiring a constant reduction in speed are fenced on both sides on public railway tracks at a distance of 50 m, and on non-public railway tracks - 15 m from the boundaries of the dangerous place with permanent signal signs “Start of dangerous places" and "The end of a dangerous place." From these signal signs, at a distance A specified in column 3 of Table 1, depending on the guide descent and the maximum permissible speed of trains, constant speed reduction signals are installed on public railway tracks, and on non-public railway tracks at a distance of the braking distance determined and installed by the owner of non-public railway tracks (hereinafter referred to as distance “T”) - speed reduction signals.
In Table 1 and in all diagrams indicated in this appendix, distances are given in meters.

Table 1

Schemes for installing permanent speed reduction discs and “Start of a dangerous place” and “End of a dangerous place” signal signs for the infrastructure owner on a single-track section are shown in Fig. 70, on one of the railway tracks of a double-track section - in Fig. 71, on both railway tracks of the double-track section - in Fig. 72, on non-public railway tracks - respectively, in Fig. 73, 74, 75.

34. Portable signals include:
1) rectangular shields, red on both sides or red on one side and white on the other;
2) square shields of yellow color (the reverse side is green);
3) lanterns on poles with red fire and red flags on poles.

35. Portable signals impose the following requirements:
1) a red rectangular shield (or a red flag on a pole) during the day and a red lantern on a pole at night - stop! It is prohibited to pass the signal (Fig. 76);

2) a yellow square shield day and night (Fig. 77) when a dangerous place is located:
on a stretch - driving at a reduced speed is allowed, there is a dangerous place ahead that requires stopping or proceeding at a reduced speed;
on the main railway track of a railway station - movement is allowed at a reduced speed; there is a dangerous place ahead that requires traveling at a reduced speed;
on other station railway tracks - it is permitted to transmit the signal at the speed specified in the warning, and in the absence of it - on public railway tracks at a speed of no more than 25 km/h, and on non-public railway tracks - at a speed of no more than 15 km/h .

The reverse side of the square shield (green) day and night (Fig. 78) on the stretch and on the main railway track of the railway station indicates that the train driver has the right to increase the speed to the set speed after passing the dangerous place with the entire train.

36. Any obstacle to the movement of trains on the stretch must be fenced off with stop signals, regardless of whether a train is expected or not.
Work areas on the stretch that require stopping trains are fenced in the same way as obstacles.
Obstacles on the stretch are fenced off on both sides on public railway tracks at a distance of 50 m, and on non-public railway tracks - 15 m from the boundaries of the fenced area with portable red signals. On public railway tracks from these signals at a distance B indicated in column 4 of Table 1, depending on the guide descent and the maximum permissible speed of trains on the stretch, three firecrackers are placed at a distance of 200 m from the first firecracker closest to the work site , in the direction from the work site, and on non-public railway tracks at a distance “T” portable speed reduction signals are installed.
On non-public railway tracks, when carriages move forward, the installation distance of portable signals increases by the length of the train operating on a particular section.
Schemes for fencing obstacles and work sites on public railway tracks on a single-track section are shown in Fig. 79, on one of the railway tracks of a double-track section - in Fig. 80, on both railway tracks of the double-track section - in Fig. 81, and on non-public railway tracks - respectively, in Fig. 82, 83, 84.

On public railway tracks, portable speed reduction signals and firecrackers must be guarded by signalmen standing with hand-held red signals 20 m from the first firecracker, and on non-public railway tracks - from speed reduction signals towards the work site (obstacle site). Portable red signals must be under the supervision of the work manager.
When carrying out work with a deployed front (more than 200 m), the work sites are fenced in the order shown in Fig. 85. On public railway tracks, portable red signals installed at a distance of 50 m, and on non-public railway tracks - 15 m from the boundaries of the area requiring fencing, must be guarded by signalmen standing near them with hand-held red signals.

If the place of an obstacle or work on a stretch is located near a railway station and it is impossible to fence this place in the established manner, then from the side of the stage it is fenced as indicated in this paragraph, and from the side of the railway station a portable red signal is installed on the axis of the railway track opposite the entrance traffic light (or signal sign “Station boundary”). At the same time, on public railway tracks with the laying of three firecrackers, guarded by a signalman (Fig. 86), and for non-public railway tracks without laying firecrackers (Fig. 87). If the location of the obstacle or work is located at a distance of less than 60 m from the entrance traffic light (or the “Station Boundary” signal sign), then firecrackers are not placed on the side of the railway station, and portable speed reduction signals are not installed on non-public railway tracks. The diagram of the obstacle fencing in front of the entrance traffic light on public railway tracks is shown in Fig. 86, and on non-public railway tracks - in Fig. 87.

On non-public railway tracks, an obstruction site for work on hauls, requiring trains to travel at a reduced speed, is fenced at a distance “T” from the boundaries of the fenced area with portable speed reduction signals.
The diagram for installing a speed reduction signal on a single-track section is shown in Fig. 88, on one of the double-track railway tracks - in Fig. 89, on both double-track railway tracks - in Fig. 90.

When a train approaches a portable yellow signal, the driver is obliged to sound one long whistle of a locomotive, multiple unit train, special self-propelled railway rolling stock, and when approaching a signalman with a manual red signal, give a stop signal and take measures to immediately stop the train in order to stop without passing the portable red signal.
To distinguish themselves from other railway workers, signalmen must wear a yellow hat with a top.
Places of obstacles to the movement of trains and places of work on multi-track sections are fenced in accordance with the procedure established by the owner of the infrastructure, the owner of non-public railway tracks.

37. If an obstacle suddenly appears on a stretch and there are no necessary portable signals, you should immediately install a stop signal at the site of the obstacle (Fig. 91): during the day - a red flag, at night - a lantern with a red light and on both sides on public railway tracks at a distance B , indicated in column 4 of Table 1, depending on the guide descent and the maximum permissible speed of trains, place three firecrackers on the stretch, and on non-public railway tracks, install a stop signal on the side of the expected train - at a distance “T”.

Firecrackers must be guarded by employees of the departments of the infrastructure owner or the owner of non-public railway tracks, who are required to stand with manual red signals at a distance of 20 m from the first firecracker towards the location of the obstacle.
Signals are installed first on the side of the expected train. On single-track sections, if it is unknown from which side the train is expected, signals are installed primarily on the side of the descent to the fenced area, and on the site - on the side of the curve or notch.
The detailed procedure for the actions of workers when fencing suddenly arisen obstacles is determined by the owner of the infrastructure, the owner of the non-public railway tracks.

38. Places through which trains can pass only with a conductor (at a speed of less than 15 km/h), as well as interlacing railway tracks on double-track sections at one level, are fenced off as a place of obstacles to movement, but without laying firecrackers. Written warnings are issued about the installation of these signals on trains.
If it is necessary to let a train pass with a conductor for which a warning has not been issued, laying firecrackers is mandatory.
If the passage of trains with a conductor is established for a long time, then portable red signals can be replaced with cover traffic lights, left in the closed position, with warning traffic lights installed in front of them (Fig. 92).

The installation locations of cover traffic lights are determined by the owner of the infrastructure, the owner of non-public railway tracks.
When the fenced area of ​​the track posts is opened on both sides, the movement of trains between these posts is carried out using one of the used means of signaling and communication without a conductor. In some cases, a conductor may be appointed to monitor the movement of a train through a fenced area at a set speed.

39. In all cases, firecrackers are placed in the amount of three pieces: two on the right rail of the railway track along the train and one on the left (Fig. 91). The distance between firecrackers should be 20 m.

40. Portable speed reduction signals and signal signs “Start of a dangerous place” and “End of a dangerous place” are installed on public railway tracks according to the diagrams shown in Fig. 70, 71, 72, and on non-public railway tracks - in Fig. 73, 74, 75.
If a place requiring a reduction in speed on a stretch is located near a railway station and it is impossible to fence it in the established manner, then from the side of the stretch it is fenced as indicated in this paragraph, and from the side of the railway station on public railway tracks - in the manner specified in Fig. 93, and on non-public railway tracks - in Fig. 94.

When approaching a portable yellow signal, the driver of a locomotive, multiple unit train, or special self-propelled railway rolling stock is required to blow one long whistle and drive the train so as to proceed through the place fenced off by portable signal signs “Beginning of a dangerous place” (Fig. 95) and “End of a dangerous place” "(Fig. 96), at the speed indicated in the warning, and in the absence of a warning on public railway tracks - at a speed of no more than 25 km/h, and on non-public railway tracks - no more than 15 km/h.
The signal sign “End of a dangerous place” is placed on the reverse side of the sign “Beginning of a dangerous place”.

Portable speed reduction signals and signal signs “Start of a dangerous place” and “End of a dangerous place” on station railway tracks and multi-track sections can be used with shortened poles.

41. Places of work on the railway track that do not require fencing with stop or speed reduction signals, but require warning of workers about the approach of a train, are fenced with portable signal signs “C” - blowing a whistle, which are installed near the railway track where the work is being carried out, as well as each adjacent main railway track. The arrangement of signal signs “C” is shown in Fig. 97, where for non-public railway tracks the distance from the work site to the signal sign “C” is equal to the distance “T”.

Portable signal signs “C” are installed in the same order at adjacent main railway tracks and during work performed, fenced by stop signals (Fig. 80, 86 - 90) or speed reduction signals.
On sections where trains operate at speeds of more than 120 km/h, portable signal signs “C” are installed at a distance of 800 - 1500 m from the boundaries of the work area.

42. Any obstacle to movement along station railway tracks and turnouts must be fenced off with stop signals, regardless of whether a train (shunting train) is expected or not.
When fencing a place of obstacle or work on a station railway track with stop signals, all switches leading to this place are set in such a position that railway rolling stock cannot enter it, and are locked or sewn up with crutches. At the site of an obstacle or work being carried out on the axis of the railway track, a portable red signal is installed (Fig. 98).
If any of these arrows are pointing towards the location of the obstacle or work and do not make it possible to isolate the railway track, such a place is fenced on both sides with portable red signals installed on public railway tracks at a distance of 50 m, and on non-public railway tracks use - 15 m from the boundaries of the obstacle or work site (Fig. 99). In the case when the points of the switches on public railway tracks are located closer than 50 m, and on non-public railway tracks - closer than 15 m from the place of obstacles or work, a portable red signal is installed between the points of each such switch (Fig. 100).

When fencing with portable red signals the location of an obstacle or work on a switch, the signals are installed: on the side of the cross - against the limit column on the axis of each of the converging railway tracks; on the opposite side on public railway tracks - 50 m, and on non-public railway tracks - 15 m from the point of the arrow (Fig. 101).

If, close to the switch that is to be fenced, there is another switch that can be placed in such a position that the railway rolling stock cannot move onto the switch where there is an obstacle, then the switch in this position is locked or sewn up. In this case, a portable red signal is not placed on the side of such an insulating arrow (Fig. 102).

When the arrow cannot be placed in the indicated position, then on public railway tracks at a distance of 50 m, and on non-public railway tracks - 15 m from the place of obstacle or work in the direction of this arrow, a portable red signal is installed (Fig. 101).
If the place of the obstacle or work is located on the entrance switch, then from the side of the section it is fenced with a closed entrance signal, and from the side of the railway station - by portable red signals installed on the axis of each of the converging railway tracks against the limit post (Fig. 103).

When the site of an obstacle or work is located between the entrance arrow and the input signal, then from the stage side it is fenced with a closed entrance signal, and from the railway station - by a portable red signal installed between the points of the entrance arrow (Fig. 104).

A switch post duty officer who discovers an obstacle at a switch must immediately install one portable red signal at the location of the obstacle (before starting repair work) and report this to the railway station duty officer.

43. A place requiring a reduction in speed, located on the main railway track of a railway station, is fenced off with portable speed reduction signals and signal signs “Start of a dangerous place” and “End of a dangerous place”, as shown in Fig. 105 and 106.

If the place requiring a reduction in speed is located on the remaining station railway tracks, then it is fenced only with portable speed reduction signals. The order of installation of these signals is shown in Fig. 107.

At railway stations of non-public railway tracks, not equipped with devices for electrical centralization of switches and traffic lights, in the event of a train stopping at the neck of the railway station and there is no passage (established distance between the axes of the station railway tracks) along adjacent railway tracks, all exits from these railway tracks are fenced with signals stops (Fig. 108).

44. Cars being repaired on station railway tracks, and cars with dangerous goods of class I (explosive materials), passenger cars standing on separate railway tracks, are protected by portable red signals installed on public railway tracks on the axis of the railway track at a distance of at least 50 m, and on non-public railway tracks - at least 15 m (on through railway tracks - on both sides, and on dead-end railway tracks - on the switch side).
If in this case the outer car on public railway tracks is located less than 50 m from the limit post, and on non-public railway tracks - less than 15 m, then a portable red signal on this side is installed on the axis of the railway track opposite the limit post.
At railway stations of non-public railway tracks, equipped with devices for electrical centralization of switches and traffic lights, railway tracks on which cars are cleaned, commercial faults are eliminated, and cars are uncoupled and maintained are equipped with fencing devices that prevent the entry of railway rolling stock.
At maintenance and repair of wagons, devices and centralized fencing of trains can be used, while the procedure for fencing trains or individual groups of wagons during their maintenance and repair, depending on local conditions, is established by the owner of the infrastructure, the owner of the non-public railway tracks.

45. When forced to stop on a stretch passenger train fencing is carried out by the conductor of the last passenger car at the direction of the driver in the following cases:
1) requests from a recovery or fire train, as well as an auxiliary locomotive, if assistance is provided from the tail;
2) if the train was sent during a break in the operation of all signaling and communication means along the correct railway track for a double-track section or a single-track section with notification of the departure of another train behind it.
The conductor of the last passenger car, protecting the stopped train, must activate the handbrake, place firecrackers at a distance of 800 m from the tail of the train, and then move away from the place of the laid firecrackers back to the train at 20 m and show a manual red signal in the direction of the section (Fig. 109).

In case of a forced stop on the stage of other trains, they are protected in cases where the departure was made in conditions of interruption of all signaling and communication means along the correct railway track for a double-track stage or single-track stage with the issuance of a notice of the departure of another train behind it. In this case, the fencing is carried out by the driver's assistant, who must immediately after stopping go to the tail of the train, check for the presence of a train signal, carefully observe the passage and, if a following train appears, take measures to stop it.
If assistance is provided to a stopped train from the head, the driver of the leading locomotive must sound a general alarm when a recovery or fire train or an auxiliary locomotive approaches; At night and during the day, if visibility is poor, turn on the spotlight.

46. ​​The conductor of the car, fencing the tail of a passenger train stopped on the stretch, returns to the train only after the recovery or fire train or auxiliary locomotive has approached and stopped, or when transferring the fencing to another employee who has approached the stopping place of the passenger train.
An assistant driver, located at the tail of a train sent during a break in the operation of all signaling and communication means, returns to the locomotive only after the next train approaches and stops or upon a signal from the driver given by the locomotive whistle, if the need for fencing has passed.

47. In areas equipped with automatic blocking, when a passenger train stops during a stage, the conductor of the last passenger car is obliged to check the visibility of train signals, carefully monitor the stage and, if a following train appears, take measures to stop it.

48. When a train is forced to stop on a double-track or multi-track section due to derailment, collision, collapsed cargo, etc., when it is necessary to fence off an obstacle to the movement of trains that has arisen on an adjacent railway track, the driver must sound a general alarm.
In this case, in the event of a stop of a passenger train, fencing is carried out from the head of the train by the assistant driver, and from the tail by the conductor of the last passenger car by laying firecrackers at a distance of 1000 m from the head and tail of the train, as shown in Fig. 110.

In addition, the driver of a passenger train reports the incident using available means of communication to the train dispatcher or duty officers at railway stations limiting the haul, as well as to the driver of the locomotive traveling along the adjacent railway track.
On non-public railway tracks, if the train is accompanied by a compiler, fencing of the obstacle site is carried out from the head of the train by an assistant driver, and from the tail by the compiler, who move to a distance “T” and show a manual red signal in the direction of the stretch, respectively, from the head and tail trains. If the train is not accompanied by a compiler, the fencing of the obstacle on the adjacent railway track is carried out by an assistant driver from the side of the expected train at a distance “T”. If the train driver receives a message about the train departing along the wrong railway track, he must use the locomotive whistle to call an assistant driver to guard the obstacle from the opposite side.
When stopping other trains, fencing is carried out by the driver's assistant by placing firecrackers on the adjacent railway track from the side of the train expected along this railway track at a distance of 1000 m from the location of the obstacle (Fig. 111). If the head of the train is located at a distance of more than 1000 m from the obstacle, firecrackers on the adjacent railway track are placed opposite the locomotive. If the train driver receives a message that a train has been sent in the wrong direction along an adjacent railway track, he must call an assistant driver via radio or locomotive whistle to lay firecrackers at the same distance from the obstacle on the opposite side, and on non-public railway tracks to protect the obstacle from the opposite side.

In areas where passenger trains operate at speeds over 120 km/h, the distances at which firecrackers must be placed are set by the owner of the infrastructure.
After laying the firecrackers, the driver's assistant and the carriage conductor must move 20 m away from the place where the firecrackers were laid back to the train and show a red signal in the direction of a possible approaching train.

49. By order of the driver of the leading locomotive, employees of the locomotive crew, conductors of passenger cars, and conductors may be involved in fencing the tail and head of a train that has a forced stop on the stretch, as well as places of obstacles for the movement of trains on the adjacent railway track of a double-track or multi-track stage.
Other workers may be involved in fencing the tail and head of a train that has a forced stop on the stretch, as well as places of obstacles for the movement of trains on the adjacent railway track of a double-track or multi-track stage, established by order, respectively, of the owner of the infrastructure or the owner of the non-public railway tracks.
When servicing locomotives of passenger trains by one driver, fencing of the train during a forced stop on a stretch is carried out by the head (mechanic-foreman) of the passenger train and the carriage conductors at the driver’s direction, transmitted via radio communication.
When servicing freight train locomotives by one driver, fencing of the train during a forced stop on a stretch is carried out in accordance with the procedure established by the owner of the infrastructure, the owner of the non-public railway tracks.

A flat screen or shield is the simplest type of acoustic design for a loudspeaker head (speaker). Most often this is a square or rectangular wooden panel of quite large dimensions. For example, to reproduce sound with a frequency of 50 Hz (λ = 680 cm) without attenuation, it is necessary that the side of the screen be at least 0.5λ, i.e. approximately 340 cm. However, good results can be obtained with a smaller panel whose side is approximately equal to a quarter of the wavelength of the lowest reproduced frequency, if the frequency response is raised at low frequencies. At the same time, this frequency cannot be lower than the main resonant frequency of the head, since this sharply reduces the sound emission from the head in the screen (18 dB/oct.).

The symmetry of the screen relative to the axis of the diffuser is undesirable, since in this case a deep dip will appear in the frequency response of the loudspeaker as a result of an acoustic short circuit at one of the frequencies. A significant improvement in frequency response can be achieved by using an asymmetrical screen or asymmetrically positioning the speaker in a properly shaped screen.

The figure above shows the dimensions of a standard flat screen for measuring loudspeaker head parameters and two ways to install them in a panel. This design is not very common due to its bulkiness and aesthetics.

Installing the screen in the corner of the room allows you to reduce its size without compromising playback low frequencies, since the walls forming the corner serve as a continuation of the screen, increasing its effective dimensions. The shield is hung from the ceiling, giving it the shape of a triangle or trapezoid. A wide gap must be left between the top edge of the shield and the ceiling, and the space behind the shield must be filled with sound-absorbing material.

Frequency response of the speaker when located in a rectangular panel. 1 – in the center, 2 – when offset along the long side

It is recommended to make the screen from thick boards, chipboard, plywood, etc. 10-20 mm thick. Preferably, the aspect ratio of a rectangular shape is from 2:1 to 3:1. It is advisable to choose the absolute dimensions such that at the lower limit of the frequency range (the resonant frequency of the speaker) the equivalent screen diameter (the diameter of a circle whose area is equal to the screen area) D is determined by the formula:

D=0.5λ/Q, Where

D– equivalent screen diameter;

λ - length sound wave at the lower limit of the frequency range;

Q- complete quality.

With such screen sizes, the frequency response will be more uniform. If the screen is made smaller, then we should expect that there will be a rolloff at the lower frequency of the range, calculated by the formula:

N=20 lg(D/ D 1 ) , Where

N– decay at the resonant frequency;

D 1 – actual screen diameter.

Example. The resonant frequency of the speaker is 85 Hz, quality factor 2. Determine the roll-off at the resonant frequency if D 1 = 0.5 m. Determine the equivalent screen diameter: D = 0.5 (343: 85) 2 ~ 1 m. When D 1 = 0.5 m at the lower limit frequency N = 20lg (1: 0.5) = 6 dB.

It is recommended to place the speaker in the center of a rectangular shield. The offset from the center reduces the developed sound pressure and worsens the frequency response. For a square shield, moving the head location improves the frequency response, although it reduces the sound pressure.

It is highly recommended to install the speaker flush with the screen panel. If the speaker is installed on the inside of the panel, a cylindrical recess (a kind of short pipe) is formed in front of it, and the column of air located in it can resonate at a number of frequencies, thereby worsening the frequency response and sound quality. When covering the front side of the screen with a grill, you need to ensure that the fabric is well stretched. From the back, on the magnet side, it is recommended to put a “skirt” on the speaker, for example made of calico.

Meet Acustic systems, in which the loudspeaker head is inserted into a hole in the wall of the room, i.e. the wall is a screen. This design solution is beneficial, but one must take into account sufficient volume in the next room. Using a wall as a screen provides a noticeable improvement in frequency response and sound quality (especially at low frequencies). The additional bag behind the speaker should be made large (for example, in the form of a hemisphere with a diameter equal to the diameter of the speaker) and filled with cotton wool to prevent unwanted resonances.

The shield can be small in size (side dimensions 40-50 cm) if the speaker reproduces frequencies above 150-200 Hz, as for example in the case of a 2.1 system, where a subwoofer plays the role of voicing low-frequency sounds.

Let's consider another calculation based on the dimensions of a flat screen (shield). We need a screen that would allow us to obtain the same sound pressure level at the lower limit of the reproduced range as at the upper limit of the piston range. fgr.v. its coverage area, i.e. equalize the sound pressure at low and mid frequencies. Meaning fgr.v. can be found from the formula: fgr.= 1.4 s / (∏d) .

Typical frequency response in the low frequency region at Q>1.93

The choice of the lower limit frequency depends on the quality factor of the head used. Frequency response shape at Q<1,93 монотонно возрастает, а при Q≥1,93 на АЧХ появляется провал на частоте ω 2 and a peak at frequency ω 1. The quality factor of the head when placed in a flat panel practically does not change. Uneven frequency response at Q<1,93 и при правильном выборе размеров экрана определяется только спадом в область более низких частот. Поэтому за нижнюю граничную частоту при Q<1,93 выбирают резонансную частоту динамика ω 0 . When Q≥1.93, the peak frequency is usually chosen as the lower limit frequency ω 1 The frequency response of the dynamics and the unevenness of the frequency response in this case is determined by the dip at the frequency ω 2. However, this slightly narrows the estimated range of reproducible frequencies compared to its value at Q<1,93.

Dependence of φ(Q) on Q

To eliminate this drawback, another method is proposed for selecting the lower limit frequency, allowing to reduce its value. Its essence lies in the fact that the cutoff frequency is selected at a frequency ω<ω 2 , at which the level of the frequency response is equal to its level at the dip frequency ω 2. Depending on the value Q this frequency may be slightly higher or lower ω 0 . Research has shown that the most rational head quality factor for open speakers is 2.4. In this case, the lower limit frequency of the open speaker fgr.n. matches the resonant frequency of the speaker ω 0 .