A helm is mainly worn when cave or wreck diving, used to protect the head on impact and also ideal to use as a place to install several lights or lightheads.

Diving helmets are worn by divers who need to speak and hear underwater. A normal diving mask and diving regulator prevent the diver from effectively communicating. Diving helments are mostly used with surface supplied diving: the helmet acts as a firm anchor point on the diver for the umbilical supplying the breathing gas. Divers do heavy or dangerous work underwater also benefit from the head protection provided by the helmet.

There are several types of diving helmets :

• the spherical copper helmets with brass and glass windows of the historical standard diving dress
• the modern commercial helmet, such as, the Kirby Morgan (http://www.divingsystems.com/History/ourhistory.html) Superlite-17B helmet
• light weight, recreational "transparent dome" type helmets

An alternative to the diving helmet that allows communication with the surface is the full face diving mask.

"Diving helmet" sometimes means a hard safety helmet like a workman's helmet that covers the top and back of the head but not the face and does not keep air in and water out.

During the First World War English Army used a very few number of diving helmets to prevent damages from the use of mustard gas because it can cause damages even only with skin contact.

There are plenty to chose from, but a low volume mask is always preferable.

A diving mask is an item of diving equipment that allows the SCUBA diver to see underwater. The mask must be constructed so that the diver can exhale through the nose into the mask to prevent the "squeeze" caused by increasing pressure during the descent in water. The mask must have a durable glass plate in front of the eyes and a "skirt" of rubber or silicone to create a watertight seal with the diver's face. A strap keeps the mask in position.

There are several specialised types of diving headgear:

• full face diving mask - often worn by working divers who need underwater verbal communication ability
• diving helmet - often worn by divers using surface supplied diving equipment
• hard hat - part of the old fashioned standard diving dress

Hoods are there for isolation, a diver loses most heat thru the skin on his/her head. This can be up to 75% off the total heat loss. Therefore a good isolation off the head is important, specially on long decompression dives.  The isolation off the hood has to be adapted to the watertemperture. Remember that water unless it is over 36 degrees Celsius allows the body to lose heat.

Tube through which a submarine or diver can draw air while underwater. When in use, the top of the snorkel tube extends above the water surface into the air. The first snorkels were probably devised in ancient times out of the hollow reeds that are common to many lakes and marsh areas. Since they are mentioned by Pliny the Elder, a Roman naturalist of the 1st cent. A.D., it is certain that such devices were in use during the early years of the Roman Empire. The first modern snorkel was devised by Leonardo da Vinci at the request of the Venetian senate. It consisted of a hollow breathing tube that was attached to a diver's helmet of leather. The present-day diver's snorkel is typically a J-shaped tube that is open at the top and has a mouthpiece at the other end. Usually no more than 2 ft (61 cm) long, the snorkel can only be used as a breathing device when a diver is swimming face down near the surface. At greater depths, the diver must hold his breath and keep his tongue over the mouthpiece to prevent water seepage. When the diver nears the surface, a strong exhalation will clear the tube of water so that breathing can begin again.

A diving regulator is a gas pressure regulator which supplies SCUBA divers with breathing gas at ambient pressure from a diving cylinder.

Types of regulator

Two stage, single hose

Most modern scuba regulators are of this type.

The first stage is a pressure reducing valve that takes gas from the diving cylinder at pressures of 200 - 300 bar (3000 - 4700 psi) and reduces its pressure down to 10 bar (140 psi) higher than ambient pressure in the hose.

The second stage valve delivers the gas from the single hose to the place it is required. It can have one of the following activation mechanisms. It could be a "demand valve" operated by the diver's inhalation from the valve. It could be manually operated valve or a solenoid-operated valve.

Demand valve second stage

The demand valve, second stage or DV is the device connected to a low pressure hose from which the diver inhales. It detects when the diver starts inhaling and supplies the diver with a breath of gas at ambient pressure. It reduces the gas pressure in the hose from 10 bar (140 psi) above ambient pressure to ambient pressure. Most modern, open circuit scuba sets use this type of second stage.

It consists of a chamber, a valve at the end of the low-pressure hose and a mouthpiece, which the diver grips between his or her teeth. A diaphragm at the front of the chamber controls the valve on the low-pressure hose. The diaphragm operates when the "purge button" on the front of the demand valve is pressed or when the diver lowers the pressure inside the chamber by trying to inhale. In either case low pressure gas is released into the chamber removing any water in there, allowing the diver to inhale and pushing the diaphragm back so that the valve closes. When the diver exhales the exhalation diaphragm flexes and allow the gas to escape to the water outside the demand valve.

Some passive semi-closed circuit rebreathers use a form of demand valve, which senses the volume of the loop and injects more gas when the volume falls below a certain level.

Manually operated second stage

This type of second stage is used in buoyancy compensator inflation valves and in rebreather loop inflation valves. A simple button allows the valve to be opened.

Solenoid operated second stage

This type of second stage is used automated fully closed-circuit rebreathers to maintain the oxygen partial pressure of the loop.

Twin-hose

This type of regulator had two wide, corrugated, breathing tubes. The first and second stages of the regulator were in a large circular valve assembly mounted on top of the cylinder pack. One-stage and three-stage regulators were known. The second, return tube was not for rebreathing but to balance the regulator's second stage diaphragm to regulate the flow of gas. Raising the mouthpiece above the regulator increased the flow of gas and lowering the mouthpiece increase breathing resistance.

The relatively large volume of the hoses forced divers to carry more weight underwater to compensate. An advantage with this type of regulator is that the bubbles leave the regulator behind the divers head increasing visibility. They have been superseded by the single hose regulator and become obsolete in the 1980s.

The twin hose mouthpiece has reappeared in modern rebreathers but as part of the breathing loop, not as part of a regulator.

Constant flow

Constant flow regulators are the earliest type of diving regulator. They are also used in active semi-closed circuit rebreathers. With a constant flow regulator the diver is provided with breathing gas at a constant rate. The only control the diver has is to open or close the valve to the cylinder. Constant flow vales consume gas less economically than demand valve regulators because gas is provided even when it is not needed.

With active semi-closed circuit rebreathers, the diver installs one of a number of different sized orifices in the valve before the dive. For safety reasons these should be chosen to provide more gas than the diver needs, to avoid hypoxia.

There were attempts at designing and using constant flow regulator before 1939, for diving and for industrial use. Examples were "Ohgushi's Peerless Respirator" where the valve was operated by the diver's teeth, and Commandant le Prieur's breathing sets (see Timeline of underwater technology).

Parts of a modern single hose regulator

Main components of a diving regulator, which supply the diver with breathing gas are:

• the first stage
• one or more low pressure hoses
• one or more demand valves or second stages

In order to monitor breathing gas pressure in the diving cylinder, a diving regulator is usually equipped with:

• the high pressure hose
• the contents gauge

In some cases, the diving regulator may be equipped with

• a pressure relief valve

First stage valve

The first stage has either an A clamp or a DIN fitting to connect it to the pillar valve of the diving cylinder. It has a number of "ports", which allow low and high-pressure hoses to transport gas to other components.

The mechanism inside the first stage can be of the diaphragm-type or the piston-type. Diaphragm regulators are simpler than piston regulators, but need more careful maintenance so are less suitable for diving at locations with limited services. With piston-type regulators, the piston is rigid and acts directly on the seat of the valve. On diaphragm-type regulators, the diaphragm is flexible and lifts the rod opens and closes gap at the seat. Both types can be balanced or unbalanced. The performance of unbalanced regulators decreases as the cylinder pressure falls, so they are only suitable for divers who only do shallow diving or for training.

As gas leaves the cylinder it decreases in pressure in a regulator, becoming very cold. In conditions where the water temperature is less than 5 °C any moisture inside the regulator may freeze, preventing the valve closing, causing a free-flow that can empty a full cylinder within a minute or two. The modern trend of using more plastics, instead of metals, within the regulators encourages freezing because it insulates the inside of a cold regulator from the warmer surrounding water. Environmental sealing and teflon coatings are used to reduce the risk of freezing inside the regulator.

Low pressure hose

All breathing regulators have a hose that connects the first stage to the demand valves. Some low pressure hoses are known as direct feeds. They supply gas to the diving suit and the buoyancy compensator inflation valves.

The first stage delivers gas at about 10 bar above the ambient pressure to low pressure hoses. That is a between the high pressure in the cylinder and the ambient pressure, that's why they are sometimes called medium pressure hoses.

Demand valve

Sometimes a regulator has more than one DV. If it is simply a spare DV for use by the diver's buddy it is generally called an octopus. Another possibility is: it could be a hybrid DV and buoyancy compensator inflation valve. Both types are called alternate air sources and more confusingly a DV on a regulator connected to a separate, independent diving cylinder would also be given that name.

Pressure relief valve

A pressure relief valve is a safety device that must be used if no demand valves are present on the regulator. It allows gas to escape from the first stage in the event of a malfunction, without over-pressurising any other regulator components, such as diving suit or buoyancy compensator inflation valves.

Normally, if present, a demand valve will vent off safely the excess gas from the first stage malfunction. This is called a free flow and is designed as a fail safe feature so that the diver can continue to breathe for a few seconds or minutes until all the gas is rapidly exhausted. If there is neither a demand valve nor a pressure relief valve there is a danger the excess gas will free flow to the buoyancy compensator or diving suit resulting in a rapid increase in buoyancy causing a potentially lethal rapid ascent to the surface.

Performance of regulators

ANSTI (http://www.ansti.co.uk/) has developed a testing machine that measures the inhale and exhale effort in using a regulator. Publication of results of the performance of regulators in the ANSTI test machine has resulted in big performance improvements.

IATD advices the use off steel or composite tanks only. The tank size or set-up may change according to the planned dive. However tanks need to hold enough gas to supply the diver during the whole dive and remain a reserve off at least 30%.  Aluminium cylinders have a lower density than steel cylinders. This can be an advantage in technical diving because it reduces the extra buoyancy the diver needs to carry many cylinders. It can be a disadvantage to divers who carry few cylinders due to the extra weight needed on the diving weighting system to counteract this buoyancy.

On all technicaldives, IATD advices to use double bladder wings. On all IATD courses these are commendatory. Minimum lift capacity is 2 x 30 kilo's.  

Features

BCs can have the following features:

• A low pressure direct feed that transports gas from diving cylinder and diving regulator to the BC.
• An inflation valve that allows gas from the direct feed into the bladders of the BC.
• A vent valve that allows gas to escape from the bladders of the BC.
• An over pressurization valve that automatically vents the bladders if the diver over inflates the BC by ascending or by injecting too much gas.
• A harness that the diver wears with straps around the torso and over the shoulders
• A plastic or metal backplate to support diving cylinders
• Pockets for carrying reels, buoys and decompression tables
• D rings or other anchor points, for clipping on other equipment such as torches, strobes, reels, cameras and stage cylinders
• Emergency inflation cylinders. This can either be a 0.5 litre air cylinder, filled from the diver main cylinder, or a small carbon dioxide cylinder. There is a risk that an emergency cylinder is accidentally opened during a dive causing a rapid ascent and barotrauma to the diver. Carbon dioxide, being poisonous, is a dangerous gas to have in the bag of a BC because that gas can be inhaled by the diver.

Types

There are three main types of BC:

• Wings consist of inflatable bladders worn behind and to the side of the diver. They are a recent development and often used in technical diving. The diver is strapped to a back plate on to which the wings are attached. The spacious location of the bladders allows their volume and therefore their buoyancy to be high: 30 litre wings are not uncommon. Heavy equipment such as diving cylinders can be fixed to or slung from the back plate. A problem with wings is their tendency to float the diver facedown at the surface, which could be lethal in the event of the diver being incapacitated.

• Stabiliser jacket, stab, waistcoat or vest BCs are inflatable vests worn by the diver around the upper torso. They typically provide up to 25 litres of buoyancy and are fairly comfortable to wear. They may float an unconscious casualty face-down.

• Adjustable Buoyancy Life Jackets, ABLJs or horsecollar BCs: are worn around the neck with straps around the waist and between the legs. They are cheap, light and small, providing up to 15 litres of buoyancy. They float an unconscious casualty face-up. But they are old-fashioned, uncomfortable with a strap between the legs and provide less buoyancy than the other types. The diver must use a separate cylinder harness as a platform for the aqua-Lung.

Attitude in the water

The attitude of the submerged diver is influenced by the BC and by other buoyancy and weight components and contributed to by the diver's body, clothing and equipment. The diver typically wishes to be positioned face-down while under water, to be able to see and swim usefully, but face-up, to be able to breathe, when on the surface.

The attitude of a static and stable object in water, such as a diver, is determined by its centre of buoyancy and its centre of mass. At equilibrium, they will be lined up under gravity with the centre of buoyancy vertically above the centre of mass. The diver's overall buoyancy and centre of buoyancy can routinely be adjusted by altering the volume of the gas in the BC, lungs and diving suit. The diver's mass on a typical dive does not generally change, although it is possible if the weight belt is jettisoned or a heavy object is picked up.

Generally, the diver has no control of the position of the buoyancy in the BC, only its quantity. By inflating the BC at the surface the conscious diver can easily float face-up. By deflating the BC underwater, the diver can easily be positioned facedown. Traditionally, weight belts or weight systems are worn with the weights on or close to the waist and are arranged with a quick release mechanism to allow them to be jettisoned to provide extra buoyancy in an emergency.

It is possible to make an unconscious diver float face up on the surface by placing buoyancy and weights so that the buoyancy raises the top and front of the diver's body and the weights act on the lower and back of the body. An inflated ABLJ invariably provides this attitude. On the other hand, an inflated stab or wings BC generally floats the diver facedown because the centre of buoyancy is not close enough to the diver's head. Potential solutions to this problem are: fixed weights on the diver's cylinder or the use of large, high-density cylinders such as a 300 bar twinset. Both solutions move the centre of mass further behind the diver resulting a face-up attitude.

Many other factors, such as the number, position and density of diving cylinders, the type of diving suit, the position and size of stage cylinders, the size and shape of the diver's body and the wearing of ankle weights influence each individual diver's attitude in the water.

History

The ABLJ was developed by Maurice Fenzy in 1961. Early versions were inflated by mouth underwater. Later versions had their own air inflation cylinder. Some had carbon dioxide inflation cylinders, a development which was adandonned when valves that allowed diver's to breathe from the BC's inflation bag were introduced. Since 1969 most modern BCs have used inflation gas from one of the diver's main gas cylinders. In 1971, Scubapro developed the Stabilizer Jacket, the first jacket-style BC, and in 1972 Watergill developed the Atpac wing.

More recent innovations for jacket BCs include, weight pouches to adjust attitude underwater, integrating weights on the BC rather than a weightbelt, and inegrated diving regulators. Innovations for wings include, weight pouches to adjust attitude underwater and the stainless steel backplate.

SUITS

Wetsuits are cheap simple diving suits that are typically used when diving in water between 10 and 30 ºC.

A modern wetsuit is mostly made from thin neoprene, which provides limited thermal protection, and lined with a nylon fabric to strengthen it and to make it easy to put on and take off. Some newer wetsuits, usually marketed as "superflex", contain spandex in addition to neoprene to allow the suit to stretch (the panels of a wetsuit of this type typically contain 15-20% spandex). This counteracts neoprene's tendency to shrink with age and also allows the wearer to grow slightly without making the suit uncomfortable.

A wetsuit allows a small amount of water into the suit, but traps this thin layer of water between the skin and the neoprene, and the body heat then warms it. The neoprene insulates the warm water layer against the surrounding cold water. The wetsuit must fit close to make the suit work efficiently, as too loose a fit will simply allow the warmed water to flush away and be replaced by cold water. The suit loses buoyancy and thermal protection as the neoprene is compressed at depth.

There is some controversy over who invented the wetsuit. Most say it was Jack O'Neill who started using neoprene, which he found lining the floor of an airliner, to make a simple vest. He went on to found the successful wetsuit manufacturer, O'Neill. But Bob and Bill Meistrell, two kids from Manhattan Beach, California, claim to have started experimenting with neoprene around 1953. Their company would later be named Body Glove.

Wetsuits come in different thicknesses depending on the conditions for which it is intended. The thicker the suit, the warmer it will keep the wearer. A thick suit is stiff, so mobility is restricted. A wetsuit is normally described in terms of its thickness. For instance, a wetsuit with a torso thickness of 5 mm and a limb thickness of 3 mm will be described as a "5/3".

Different shapes of wetsuit are available, from the "shorty" that covers the torso and has short arms and short legs, the jacket covering the torso and arms, the "long johns" that covers the torso and legs only and the "full suit" or "steamer" that covers the torso and the full length of the arms and legs. Some suits are arranged in two parts; the jacket and long johns can be worn separately in mild conditions or worn together to provide two layers of insulation around the torso in cold conditions.

Usually they have no feet or hood, and the diver must wear separate boots and hood made from wetsuit material.

Drysuits are used typically when diving in water temperatures between 0 and 15 ºC (32 to 60 ºF).

Seals at the wrists and neck prevent water entering the suit. Even so, the diver will be damp after a dive in a drysuit due to sweat and condensation. The seals are either made from latex rubber or neoprene. Latex seals survive for a maximum of two years but are supple. Neoprene seals last longer but let more water enter because, being stiffer, they do not make effective seals in the contours of the wrist and neck.

A modern drysuit has an air inflation valve, which lets the diver control the buoyancy of the suit by injecting gas from the diving regulator to avoid squeeze during descent. Some old-type frogman's drysuits had a small "jack cylinder" to be inflated from, or the frogman (who was using an oxygen rebreather and so limited to about 30 feet (10 m) depth) had to put up with the suit squeeze.

A drysuit is intended to be worn over an insulating undersuit such as a Thinsulate (http://www.dui-online.com/newsite/dw_thinsulate.htm) or Polar Bear (http://www.polarbears.co.uk/). Some divers wear a wetsuit under the drysuit instead.

A typical drysuit has an air vent valve , which lets the diver vent off higher pressure gas from the suit during the ascent. Vent valves can be automatic , operating as pressure relief valves, or manual , where the diver must raise the valve to vent. Automatic vents are generally located at the shoulder and manual vents are located at the wrist. Some drysuits have no vents, but the diver must pull one of the wrist or neck seals open to vent the drysuit.

Most drysuits have built-in boots, but some have ankle seals instead.

Modern drysuits have a zipper, for entry and exit, across the back of the shoulders, or diagonally across the front of the torso, or straight down the middle of the front. At least one make of old-type British frogman's drysuit was one-piece with a wide neck hole for entry; the bottom of the hood and the edge of the suit's neck hole were clamped together by a large circular steel clamp around his neck; there was a watertight seal in the bottom of the hood.

There are two types of drysuit:

• Membrane dry suits are made from materials with low thermal insulation such as vulcanised rubber or a trilaminate of nylon, butyl rubber and nylon. So the diver must wear an insulating undersuit. Membrane drysuits are comfortable to put on, get off and wear. They can be unreliable because the suit’s buoyancy and insulation depends on the air trapped in the under suit: if the suits is punctured the buoyancy and insulation is lost. Some divers in warm water wear a membrane drysuit without an undersuit. Membrane drysuits may also be constructed with a waterproof and breathable membrane to enable comfortable wear for periods out of water.

• Neoprene dry suits are constructed from neoprene, a buoyant and thermally insulating material. This built-in buoyancy and thermal protection makes them safer to wear than membrane dry suits when punctured because they keep some of those properties when flooded. Being made of a fairly rigid heavy material, they are difficult to get on and off, and their buoyancy and thermal protection decreases with depth as the neoprene is compressed. Neoprene also tends to shrink over the years. An alternative is crushed neoprene, which is less susceptible to volume changes when under pressure and shrinks less.

Semi-dry suits are used typically when diving in water temperatures between 10 and 20 ºC (50 to 70 ºF). They are effectively a thick wetsuit with better-than-usual seals at wrist, neck and ankles.

The seals limit the volume of water entering and leaving the suit. The diver gets wet in a semi-dry suit but the water that enters is soon warmed up and does not leave the suit readily, so the diver remains warm. The trapped layer of water does not add to the suit's insulating ability. Any residual water circulation past the seals still causes heat loss. But semi-dry suits are cheap and simple compared to dry suits. They are made from thick neoprene, which provides good thermal protection. They lose buoyancy and thermal protection as the trapped gas bubbles in the neoprene compress at depth. Semi-dry suits can come in various configurations including a single piece or two pieces, made of 'long johns' and a separate 'jacket'. Semi dry suits do not usually include boots, so a separate pair of insulating boots are worn.

Gloves either wet or dry are to be used with enough isolation the dive the planned dive in comfort.

Gloves either wet or dry are to be used with enough isolation the dive the planned dive in comfort.

Fins should be able to propel the diver with all equipment needed during the dive

All divers must carry at least 3 reels one for every smb and 0ne for the liftbag. During dives these reels may be used for other purposes such as cave or wreck penetrations. also called

All divers must carry 2 surface marker buoys, one must be red and to be used during normal ascents. The second must be yellow and only be used on ascents when problems evolved and assistance is needed. Both smb's must have a lift capacity off at least 25 kg and both must have there own reel. During dive where there are many divers it is advisable to have you're name on the top end off the smb.

A Surface Marker Buoy, SMB or simply a blob is an inflatable buoy used by SCUBA divers, with a line, to mark the diver's position to their surface, safety boat whilst the diver is underwater.

SMBs are inflated on the surface before diving to mark the diver's position in these circumstances:

• during a drift dive or night dive so the dive boat can follow the divers
• where there is boat traffic making diving more hazardous

Divers need to consider some configuration options and features when using SMBs:

• A closed SMB, with a valve which you blow through, is likely to be more reliable, by remaining inflated, than an open ended buoy or a delayed buoy which seals itself as it inflates
• To avoid losing the reel, the reel needs a lanyard to attach the diving reel to the diver: this can :
  • either clip to the buoyancy compensator or go around the wrist
  • or be long enough to float above the diver and stay out of the way. If the lanyard clips to the BC, take care to release if there are boats around (boats on the surface have been known to drag divers up by their SMB reels).
    The DIR diving philosophy generally considers unsafe any attachment to equipment or objects which end above the water surface, due to high risk associated with dragging the diver upwards in spite of their decompression obligation or maximum ascent speed limit.

A specialised form of SMB is the decompression buoy.

decompression buoy, deco buoy or delayed SMB is an item of diving equipment used by SCUBA divers to mark their position whilst underwater doing decompression stops. They are similar to Surface Marker Buoys but deco buoys are launched whilst the diver is submerged. Alternative solutions to marking one's position while doing decompression stops are diving shots and decompression trapezes.

Deco buoys are inflated underwater before or during the ascent phase of the dive. A reel and line connect the buoy on the surface to the diver beneath the surface. The buoy marks the diver's position underwater so the boat safety cover can locate the diver.

There are at least four methods of keeping the air in the inflated deco buoy. The buoy can be be:

• open ended (preferably with small independent weight to keep the opening submerged)
• open ended self sealing buoys (the air in the buoy expands as the buoy ascends closing a neck at the bottom of the buoy)
• sealed, with an inflation valve and a pressure relief valve
• sealed, with a built in air supply and a pressure relief valve

Divers of some training organisations carry two differently coloured deco buoys underwater so that they can signal to their surface support for help and still remain underwater decompressing. For example, a red buoy indicates normal decompression and a yellow buoy indicates a problem, such as shortage of gas, that the surface support should investigate and resolve. Some types of buoy provide an attachment for a strobe, cyalume stick or writing slate, which can convey signals to the surface support.

Several common problems are encountered when deploying deco buoys :

1. The diving reel jambs after the buoy is inflated (dragging the diver up). To avoid this:
   • use a simpler system or a reel which cannot jamb (e.g. a weighted spool of line)
   • detach the lanyard connecting the diver to the reel before inflating the buoy (and ensure no equipment is trapped in the buoy or reel)
   • attach two reels to each other in series. If one fails the other is unlocked to reel out its line.
2. Part of the diver's equipment gets trapped in the deco buoy (dragging the diver up). To avoid this tie the lanyard of the reel to something solid on the sea bed before inflating the buoy (so you have time to sort the problem out)
3. The diver removes the primary demand valve from his or her mouth to inflate the buoy, and is therefore at a disadvantage in dealing with any other problems that might arise as the deco buoy goes off. There are a number of ways to avoid this:
   • Use a deco buoy with its own air supply
   • Use a secondary demand valve, such as an octopus, to inflate the buoy
   • Use a sealed buoy with an inflation valve, which is filled by blowing directly into the valve inlet or by attaching a medium-pressure inflation hose from the buoyancy compensator or dry suit. The valve does not retain the hose connector, like the BCD or suit inflator valve, and the hose can be easily pulled off the valve when the buoy is sufficiently filled.
   • Hold an open ended buoy above the primary demand valve and direct several exhalations up into the open end of the buoy. This technique is also useful in cold conditions to prevent freeflows caused by pressing purge buttons.

A red liftbag must be carried with a liftcapacity off at least 65kg.

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