Cable and Wires

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Cables are, to put it simply, a number of wires, usually held together in a protective cover. The name derives from the nautical term for when several ropes are intertwined to create a stronger line. Cables are used for a wide array of functions, both domestically and in industry.

The History Of Cables

The most basic cable is an unshielded twisted pair of thin copper wires, used for basic telecommunications, such as wiring up a doorbell or loud speakers. This type of cable was invented by Alexander Graham Bell to help reduce interference. The world’s largest cables are also used for telecommunications. These are submarine cables such as The Transatlantic telegraph cable, which stretches across the Atlantic Ocean from Foilhommerum Bay, Valentia Island in Western Ireland to Heart's Content in Eastern Newfoundland. This cable is approximately 2130 miles long.

Network cable

Network cables are used to connect multiple network devices together, most notably to connect computers to Internet routers, printers, scanners, digital cameras and mobile phones. Network cables utilise several different types of cable construction depending on their usage. All network cables use twisted pairs of copper wires to provide connectivity with reduced interference.

The twisted pair network cable is the most basic form of cable and it is unshielded (UTP), shielded (STP), or foil screened (FTP). All forms of network cable are made with the same objective in mind, which is to provide a reliable connectivity of electronic equipment.

FTP cables contain multiple twisted pairs, which are enclosed in a sheath of aluminium. FTP cables require more care in earthing and when connecting to UTP cable electrical impedances must be matched.

Shielded network cables have an additional layer of shielding material that further reduces external interference. The shield around the cables acts as a guard and also drains induced current surges to earth, via a Power-over-Ethernet (PoE) adaptor or the switch.

Shielded cable is thicker, heavier and stiffer than unshielded cable. This can make networking many computers more difficult without some good cable management. Shielded cable is also more expensive, and while the costs are small for home use, large businesses with hundreds or thousands of computers and peripherals spread over several floors quickly see a large part of their IT budget disappear in cables alone.

However, a good quality cable is essential to ensure that network communications do not suffer from interference. The greater the number of cables and sources, the greater the interference will become.

The best network cables today are those that meet Category 5e specification. This is an enhancement on the previous Cat 5, which is a standard for providing performance up to 100 Mhz. Most Cat 5 cables are unshielded and rely on the twisted pairs and differential signalling for noise rejection.

4mm cables

4mm cables are twin and earth electric cables, often called T&E cables, or simply power cables. 4mm cables carry mains electricity and are made from two individually insulated current carrying conductors and a single uninsulated conductor. The twin cables are for live and neutral current and the single uninsulated conductor is for the earth. 4mm twin and earth cables have stranded conductors and a solid circuit protective conductor (CPC).

This is the most common form of cable used to wire up homes with electricity. The cables often have a grey PVC cover to provide additional protection. In the short-term cables require protection from physical interference, which usually happens during construction. In the longer term the most common problem for any cable is exposure to moisture, which can cause decay.

Twin and earth electrical cables should be constructed to at least BS6004 standard, which are non-armoured and PVC insulated. These cables are intended for voltages up to and including 450/750 V.

VGA cable

VGA cables carry information from a computer to a visual display. VGA stands for Video Graphics Array and was first used by IBM, in 1987, to describe the connection between the computer and video display. Sometimes VGA is used to describe the display it generates, specifically the 640x480 pixel resolution display, which the cable carried.

IBM’s Extended Graphics Array (XGA) standard has now officially replaced VGA. VGA analogue interfaces today can be used for high definition video including 1080p and higher. The quality of VGA cable can have a noticeable effect on picture quality, especially as cable length is increased. High Definition VGA Cable is used mostly in modern gaming consoles and low quality cables connected to large screen televisions will quickly lead to a loss in picture quality.

Heavy-duty cable ties

Heavy-duty cable ties should be used when bundling several individual cables together. They are sometimes called zip ties or tie-wrap and are designed for bunching electric and network cables together.

They are generally made from durable Nylon and they are closed tight using a simple pawl mechanism (ratchet). The teeth of the pawl prevent the tie from opening once it is pulled closed.

For indoor use, a standard natural tie is sufficient; however, for outdoor use where the cables will be exposed to sunlight it is recommended that a UV Black tie (2% carbon black) be used. The 2% carbon black protects the polymer chains in the nylon from being damaged by UV radiation.

Cable ties have some unusual alternative uses. Some cyclists attach them to their cycle helmets to deter magpies. The police and military, in many countries, have also used them as handcuffs. They are very hard to break and are very light, so a single officer can carry many.

Armoured cable

Armoured cable is a power cable that has been reinforced with either aluminium wire armour (AWA) or steel wire armour (SWA). The armoured layer is between the outer PVC and an inner sheath that holds the twin and earth cables. The purpose of the armoured layer is to provide protection from mechanical interference.

Whereas 4mm cable is only suitable in domestic buildings, armoured cable can be used outside and underground. In domestic projects armoured cable is used to run electric cables around the outside of buildings to avoid having to access existing runs within wall cavities and under floorboards.

In a standard armour cable each conductor has a cross-linked polyethylene insulation and these are encased in a PVC sheath. The steel wire armour surrounds the sheath and a black UV resistant outer sheath encases the cable.

Alternative armour cables have a LS0H sheath that emits very low levels of smoke when exposed to fire, and 11kV Cable, which has several additional layers of protection around each conductor plus an additional metallic screen.

Armoured cables are used on many large industries, such as power and distribution networks, transport and railways networks and heavy industry where there is a constant risk of accidental cable damage.

Trunking cable

Trunking cable is a solid encasement to protect cables from possible damage. There are various types of trunking to suit different needs. Basic trucking is an encased D shaped tube, which can be glued to a floor or wall. The D shape provides resistance to pressure from above to prevent cables being crushed under foot.

There are some decorative types of wall mounted and floor trunking to help make electric cables look more aesthetically appealing. For cables running across the floor with heavy footfall, a rubber floor cable cover is often recommended.

Heavy-duty trunking is used for carrying electrical cables underground or through wall cavities. Heavy-duty trunking is usually a large conduit with inspection hatches at regular intervals to allow cables to be tested and replaced.

Good trunking is a vital part of good cable management. Although you should always be using high quality cables that are suitable for the conditions in which they are placed. It is always sensible to place cables in some trucking if possible, especially when they are running under a solid floor or within concrete or brick walls.

Screened cable

Screened cable, also known as shielded cable, is a cable with a protective layer to reduce electrical noise from affecting signals. Shielded cable will also reduce electromagnetic radiation that may interfere with other devices.

Shields are made of braided strands of copper or aluminium, or a non-braided spiral winding of copper tape, or a layer of conducting polymer. The shield is usually covered with a jacket that protects the shielding from physical damage. The purpose of the shield is to act as a Faraday cage around the core wires so that any interference is transferred around and along the outside of the cables, rather than into them.

Shielded cables are usually used in high-tech audio equipment, microphones and loudspeakers. Medium and high voltage power cables are also shielded to prevent electrostatic fields forming around the conductor. Unshielded high voltage power cables can cause electric shocks.

Cable Trays

Cable trays are heavy-duty conduits for electrical and communications cables in buildings. They are usually used when it is not possible to run cables beneath floorboards or through walls, such as in large open plan buildings.

Most trays are constructed from galvanised steel, aluminium or glass-fibre reinforced plastic.

They are extremely useful in buildings where additional cables are likely, which is why they are so popular in offices. It is possible to upgrade entire networks without having to contract builders to repair walls or replace flooring.

One of the biggest benefits of cable trays is that cables can be laid directly into them. With conduit the cables need to be feed through, which is impractical across larger distances.

Some cable trays have solid undersides that increase strength and protection, but make it harder to access the cable. Many types of tray have holes at regular intervals through which cables to pass. Many trays also have holes on the underside to aid ventilation and to drain water.

Trays designed to carry power cables and communications cables together often have cable management channels to keep power cables separate. Most trays come with additional tray fittings to ensure that cables are fixed in place correctly and safely. To prevent the risk of fires spreading along tray channels, fireproof coatings should be used on installed cables. It is important to keep cable trays clear of combustible dust.

Submarine cables

There are more than 200 submarine cables carrying communications around the globe today. Their presence goes mostly unnoticed by the general public; it is only following major natural disasters such as the Japanese earthquake in 2011 when their sudden absence makes them become so apparent.

Emerald Networks, a submarine cable manufacturer, have recently announced that they are teaming up with the UK’s Geo Networks to construct two new optical fibre routes from Dublin to London. Emerald Networks currently manage the “Emerald Express”: a line of submarine cables between Ireland and the USA. This will be their first penetration into the UK market and provide access to mainland Europe.

Submarine cables have been providing global communications for over 150 years and are still the best method for transporting large packets of data. Submarine cables are today the most advanced type of cable, using many of the cable construction methods mentioned above. They have up to 7 layers of protective casing outside the optical fibres, with a petroleum jelly layer, copper tubing, polycarbonate, aluminium water barriers, reinforced armoured steel wires, Mylar tape and an outer polyethylene casing. Submarine cables are made to last.

If you need help choosing the right cable for your project get in contact and we will be happy to assist.