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Light bulb sockets, light sockets lamp sockets or lampholders provide electrical connections to the lamps and support it in the lighting fixture. The use of sockets allows lamps to be safely and conveniently replaced (re-lamping). There are many different standards for these lampholders, created by de facto and by various standards bodies. A general coding system is a letter or abbreviation followed by a number. Some miniature lamps have wire leads suitable for direct connection to wires; some reflector lamps have screw terminals for wire connections.

The most common type of sockets for mains electricity are Edison screws, used in continental Europe and North America, while bayonet mounts dominate in the Commonwealth countries and in the automotive industry. Fluorescent lamps require a different, typically four-pin design. A broad variety of other socket designs exists, applied for specialized lamp constructions.

Edison Screw Bases

E10 Miniature (Flashlight lamp)
E11 Mini-Candelabra
E12 Candelabra
E14 European
E17 Intermediate
E26 Medium
E27 Medium
E39 Mogul
E40 Mogul
3-Way (modified medium or mogul socket with additional ring contact for 3-way lamps)
Skirted (PAR-38)
The light bulb commonly used since the early 20th century for general-purpose lighting applications, with a pear-like shape and an Edison screw base, is referred to as an "A-series light bulb."

Bayonet Styles

Main article: Bayonet mount
BA9s Miniature bayonet
BA15s Single Contact Bayonet
BA15d Double Contact Bayonet
Bay15d Indexed DC Bayonet
Bay 22 Double Contact Bayonet
Bayonet Candelabra with pre focusing collar
P28s Medium prefocus
P40s Mogul prefocus
Bi-Post

Main article: Bi-pin connector

115-volt airway beacon light bulb with a Mogul bi-post base

With bi-post bases, lamp orientation is fixed so filament will always be in the focal plane. Filament configurations such as the C13D (coiled, zig-zagged) emit far more light perpendicular to the zig-zag than parallel to it.

Mogul bi-post (G38) can handle up to 100 Amps and is used with searchlights, film & stage lighting fixtures 1000 watts or larger. Incandescent, halogen and HMI light sources all use this design.
Medium bi-post (G22) is used with film and stage lighting fixtures between 250 and 1000 watts (the development of the T14 base up to horizon design for ellipsoidal spotlights was one of the most important innovations of the mid 20th century).
Mini bi-post (G4-G6)
Common types:

G4 - 4mm pin spacing
GU4 & GZ4 - are same as G4 and only denote what lamp mount clip is needed to hold the actual light bulb in place
G5.3 - 5.3mm pin spacing
GU5.3, GX5.3, GY5.3, GZ5.3 - all are same as G5.3 and only denote what lamp mount clip is needed to hold the actual light bulb in place
G6.35 - 6.35mm spacing
GY6.35 & GZ6.35 - all are same as G6.35 and only denote what lamp mount clip is needed to hold the actual light bulb in place
G8 - 8m pin spacing
GU8 - same as G8 but denoted what lamp mount clip is needed to hold the actual light bulb in place
GY8.6 - 8.6mm pin spacing
G9 - 9mm pin spacing
G12 - 12mm pin spacing
Bi-Pin Connector

Main article: Bi-pin connector

Metal halide lamp with G8.5 base

Medium bi-pin is used on each end of a T12 fluorescent lamp
Mini bi-pin is used with MR16 halogen lamps
The two-pin socket is an update of the bi-post design with smaller pins designed to reduce the cost of manufacture. The 1000-watt FEL medium two-pin base halogen lamp allows designers to insert the lamp into the end of the ellipsoidal reflector through a smaller hole than previously possible with conventional incandescent lamps. This improves efficiency compared to the older side-inserted lamp or a double-ended lamp which requires two holes. One variation is the polarized two-pin socket – used primarily in projectors, which defines the exact positioning of the filament on one side. This improves the "point source" characteristic necessary for building complex optical systems.

Another facet of the two-pin design is that many new designs of lamps use baseless glass envelopes. The wire leads are thickened and crimped in the glass envelope of the lamp base. The MR16 is an example of this design; the actual lamp is inserted into the reflector with the leads sticking out and a ceramic paste used to glue it in.

Wedge Base

Main article: Wedge base
Miniature lamps may have a wedge base made of glass or plastic. The base may be an extension of the glass envelope of the bulb, with the wire leads of the lamp folded up at the base. Some wedge bases are made of plastic and slipped over the wire leads. A wedge base holds the lamp by spring compression in the socket. The lamp is inserted and removed without twisting. Wedge base lamps are widely used in automotive applications, and many Christmas lights strings use plastic wedge-based bulbs.

Fluorescent Tubular Lamp Standards

Main article: Fluorescent-lamp formats
Fluorescent Linear Tube Light bulbs are measured in 8th's of inches. So a T12 fluorescent is 12 - 8th's of an inch in diameter or 12/8 = 1.50"

T4 - 4/8 or 0.500" in diameter
T5 - 5/8 or 0.625" in diameter
T8 - 8/8 or 1.00" in diameter
T10 - 10/8 or 1.25" in diameter
T12 - 12/8 or 1.50" in diameter
SOURCE: WIKIPEDIA 2017
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TV Aerial Plug

A TV aerial plug is a colloquial name for a connector used to connect coaxial cables with each other and with terrestrial VHF/UHF roof antennas, antenna signal amplifiers, CATV distribution equipment, TV sets and FM / DAB-radio receivers.
In Europe and Australia the Belling-Lee connector (IEC 61169-2 radio-frequency coaxial connector of type 9,52) is commonly used for this purpose.

IEC 169-2 male and female connector.JPG


Male (left) and female (right) Belling-Lee connectors

The Belling-Lee connector or IEC 61169-2 radio-frequency coaxial connector of type 9,52, known colloquially in countries where it is used as a TV antenna connector as a PAL antenna connector, IEC antenna connector, or simply as a TV aerial plug, is commonly used in Europe and Australia to connect coaxial cables with each other and with terrestrial VHF/UHF roof antennas, antenna signal amplifiers, CATV distribution equipment, TV sets, and FM and DAB radio receivers. It is one of the oldest coaxial connectors still commonly used in consumer devices.[citation needed]

It was invented at Belling & Lee Ltd in Enfield, United Kingdom around 1922 at the time of the first BBC broadcasts.

The "9,52" in the name "IEC 61169-2 radio-frequency coaxial connector of type 9,52" refers to the outer diameter of the male connector, which is 9.525 millimetres (0.3750 in).

In their most common form the connectors just slide together. There is, however, also a screw-coupled variant which is specified to have a M14×1 thread.

Regular and miniature Belling-Lee plugs

There is also a miniature Belling-Lee connector which was used for internal connections inside some equipment (including BBC RC5/3 Band II receiver and the STC AF101 Radio Telephone). The miniature version is only about 4.4 millimetres (0.17 in) in diameter.
Belling Lee Limited still exists as a wholly owned subsidiary of Dialight, since 1992.

An electrical connector, is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs (male-ended) and jacks (female-ended). The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices.[ An adapter can be used to effectively bring together dissimilar connectors.

Hundreds of types of electrical connectors are manufactured for power, signal and control applications. Connectors may join two lengths of flexible copper wire or cable, or connect a wire or cable to an electrical terminal.

Electronic symbols for male-ended and female-ended connectors. (SEE BELOW)

Splitters can be used to run aerial cables for more than 1 television. (SEE BELOW)

Male (left) and female (right) Belling-Lee connectors. (SEE BELOW)
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What does it mean to be a conduit?

Definition of conduit. 1 : a natural or artificial channel through which something (such as a fluid) is conveyed a conduit for rainwater. 2 archaic : fountain. 3 : a pipe, tube, or tile for protecting electric wires or cables.
Here is a list of your most common EC's.
Type 1 - Rigid Non Metallic Conduit (PVC)
Type 2 - Rigid Metal Conduit (RMC) / Rigid Steel Conduit (RSC)
Type 3 - Intermediate Metal Conduit (IMC)
Type 4 - Galvanized Rigid Conduit (GRC)
Type 5 - Electrical Metal Tubing (EMT)
Type 6 - Flexible Metal Conduit (FMC)
Conduit Fittings

Despite the similarity to pipes used in plumbing, purpose-designed electrical fittings are used to connect conduit.

Box connectors join conduit to a junction box or other electrical box. A typical box connector is inserted into a knockout in a junction box, with the threaded end then being secured with a ring (called a lock nut) from within the box, as a bolt would be secured by a nut. The other end of the fitting usually has a screw or compression ring which is tightened down onto the inserted conduit. Fittings for non-threaded conduits are either secured with set screws or with a compression nut that encircles the conduit. Fittings for general purpose use with metal conduits may be made of die-cast zinc, but where stronger fittings are needed, they are made of copper-free aluminum or cast iron.

Couplings connect two pieces of conduit together.

Sometimes the fittings are considered sufficiently conductive to bond (electrically unite) the metal conduit to a metal junction box (thus sharing the box's ground connection); other times, grounding bushings are used which have bonding jumpers from the bushing to a grounding screw on the box.[8]

Unlike water piping, if it the conduit is to be watertight, the idea is to keep water out, not in. In this case, gaskets are used with special fittings, such as the weatherhead leading from the overhead electrical mains to the electric meter.

Flexible metal conduit usually uses fittings with a clamp on the outside of the box, just like bare cables would.

Conduit bodies

A conduit body can be used to provide pulling access in a run of conduit, to allow more bends to be made in a particular section of conduit, to conserve space where a full size bend radius would be impractical or impossible, or to split a conduit path into multiple directions. Conductors may not be spliced inside a conduit body, unless it is specifically listed for such use.

Conduit bodies differ from junction boxes in that they are not required to be individually supported, which can make them very useful in certain practical applications. Conduit bodies are commonly referred to as condulets, a term trademarked by Cooper Crouse-Hinds company, a division of Cooper Industries.

Conduit bodies come in various types, moisture ratings, and materials, including galvanized steel, aluminum, and PVC. Depending on the material, they use different mechanical methods for securing conduit. Among the types are:

L-shaped bodies ("Ells") include the LB, LL, and LR, where the inlet is in line with the access cover and the outlet is on the back, left and right, respectively. In addition to providing access to wires for pulling, "L" fittings allow a 90 degree turn in conduit where there is insufficient space for a full-radius 90 degree sweep (curved conduit section).
T-shaped bodies ("Tees") feature an inlet in line with the access cover and outlets to both the cover's left and right.
C-shaped bodies ("Cees") have identical openings above and below the access cover, and are used to pull conductors in a straight runs as they make no turn between inlet and outlet.

source: wikipedia 2107
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What is an IP rating?
IP (or "Ingress Protection") ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies (tools, dirt etc) and moisture.

What does IP rating stand for?
The IP rating of an enclosure, or Ingress Protection Rating specifies how resistant the device is to foreign objects and moisture. The first digit represents foreign objects. The range is from 1 (objects greater than 50 mm) to 6 (completely dust tight).

What does IP65 water resistant mean?
Example :With an IP65 rating, the LEDs can be used in an outside setting and are water-resistant but they are not waterproof and are not suitable to be submerged. An IP68 can be submerged in water.

What does waterproof IP68 mean?
The Samsung Galaxy S7 and S7 edge are built to do. more, in more places. With an IP68 rating, they're water resistant to a maximum depth of 1.5m. for up to 30 minutes, and are protected from dust, dirt and sand - all without the need for extra. caps or covers.

What is an IP44 rating?
IP rating stands for 'Ingress Protection' and is always followed by 2 characters. ... The higher the IP rating the more protected the light is. All the products on IP44-lights.co.uk are IP44 rated or higher (higher level of protection). IP44 is the most common IP rating used in bathroom lighting.

What is IP66/65/67 weatherproof rating?

The Mysteries of IP65, IP66, and IP67 Rated Enclosures Explained
IP Rating Protection
IP65 Enclosures Able to protect against water jets
IP66 Enclosures Able to protect against powerful water jets
IP67 Enclsoures Able to protect against Immersion up to 1 m

What is the meaning of IP20?
The first number is the protection rating against solid objects and the second number is the protection against liquids. For example, using the listing below, IP20 means you are protected again solid objects up to 12mm (2) but there is no protection against liquids (0).

IP is an acronym "Ingress Protection". It is a measurement of the protection an item will have against solid objects (dust, sand, dirt, etc.) and liquids.

An IP rating is comprised of 2 numbers. The first number refers to the protection against solid objects (dust, etc) and the second number refers to protection against liquids.

What are IP ratings and what is IP65?


SOURCE: WIKIPEDIA & https://www.flexfireleds.com 2017
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An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that when connected to an external circuit will flow and deliver energy to an external device. When a battery is connected to an external circuit, electrolytes are able to move as ions within, allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit. It is the movement of those ions within the battery which allows current to flow out of the battery to perform work. Historically the term "battery" specifically referred to a device composed of multiple cells, however the usage has evolved additionally to include devices composed of a single cell.

Primary (single-use or "disposable") batteries are used once and discarded; the electrode materials are irreversibly changed during discharge. Common examples are the alkaline battery used for flashlights and a multitude of portable electronic devices. Secondary (rechargeable) batteries can be discharged and recharged multiple times using an applied electric current; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and smartphones.

Batteries come in many shapes and sizes, from miniature cells used to power hearing aids and wristwatches to small, thin cells used in smartphones, to large lead acid batteries used in cars and trucks, and at the largest extreme, huge battery banks the size of rooms that provide standby or emergency power for telephone exchanges and computer data centers.

Batteries have much lower specific energy (energy per unit mass) than common fuels such as gasoline. In automobiles, this is somewhat offset by the higher efficiency of electric motors in producing mechanical work, compared to combustion engines.

Primary

Main article: Primary cell
Primary batteries, or primary cells, can produce current immediately on assembly. These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells. In general, these have higher energy densities than rechargeable batteries, but disposable batteries do not fare well under high-drain applications with loads under 75 ohms (75 Ω). Common types of disposable batteries include zinc–carbon batteries and alkaline batteries.

Secondary

Main article: Rechargeable battery
Secondary batteries, also known as secondary cells, or rechargeable batteries, must be charged before first use; they are usually assembled with active materials in the discharged state. Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical reactions that occur during discharge/use. Devices to supply the appropriate current are called chargers.

The oldest form of rechargeable battery is the lead–acid battery, which are widely used in automotive and boating applications. This technology contains liquid electrolyte in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas it produces during overcharging. The lead–acid battery is relatively heavy for the amount of electrical energy it can supply. Its low manufacturing cost and its high surge current levels make it common where its capacity (over approximately 10 Ah) is more important than weight and handling issues. A common application is the modern car battery, which can, in general, deliver a peak current of 450 amperes.

The sealed valve regulated lead–acid battery (VRLA battery) is popular in the automotive industry as a replacement for the lead–acid wet cell. The VRLA battery uses an immobilized sulfuric acid electrolyte, reducing the chance of leakage and extending shelf life. VRLA batteries immobilize the electrolyte. The two types are:

Gel batteries (or "gel cell") use a semi-solid electrolyte.
Absorbed Glass Mat (AGM) batteries absorb the electrolyte in a special fiberglass matting.
Other portable rechargeable batteries include several sealed "dry cell" types, that are useful in applications such as mobile phones and laptop computers. Cells of this type (in order of increasing power density and cost) include nickel–cadmium (NiCd), nickel–zinc (NiZn), nickel metal hydride (NiMH), and lithium-ion (Li-ion) cells. Li-ion has by far the highest share of the dry cell rechargeable market. NiMH has replaced NiCd in most applications due to its higher capacity, but NiCd remains in use in power tools, two-way radios, and medical equipment.

In the 2000s, developments include batteries with embedded electronics such as USBCELL, which allows charging an AA battery through a USB connector, nanoball batteries that allow for a discharge rate about 100x greater than current batteries, and smart battery packs with state-of-charge monitors and battery protection circuits that prevent damage on over-discharge. Low self-discharge (LSD) allows secondary cells to be charged prior to shipping.

SOURCE: WIKIPEDIA 2017
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A touch-sensitive lamp is one that is activated by human touch rather than a flip, pushbutton, or other mechanical switch. These lamps are popular as desk and nightstand lamps. They act on the principle of body capacitance. Touch-sensitive lamp switches may be dimmable, allowing the brightness of the lamp to be adjusted by multiple touches. Most stop at level 3, which is for the brightest use.

SOURCE: WIKIPEDIA 2017

How do touch-sensitive lamps work?

Switches that are sensitive to human touch -- as opposed to switches that must be flipped or pushed to make and break a mechanical connection -- have been around for many years. They certainly have advantages, and the most important is the fact that dirt and moisture cannot get into the switch to gum it up or damage it. Over the years, many different properties of the human body have been used to flip touch-sensitive switches:
Temperature - The human body is generally warmer than the surrounding air. Many elevators therefore use buttons that are sensitive to the warmth of the human finger. These buttons, of course, don't work if you have cold hands. The motion-sensitive lamps you see on people's patios also sense the heat of the human body.
Resistance - The human body, being made mostly of water, conducts electricity fairly well. By placing two contacts very close together, your finger can close the circuit when you touch it.
Radio reception - You may have noticed that, when you touch an antenna, the reception gets better on a TV or radio. That's because the human body makes a pretty good antenna. There are even small LCD TVs that have a conductive neck strap so that the user acts as the antenna! Some touch-sensitive switch designs simply look for a change in radio-wave reception that occurs when the switch is touched.
Touch-sensitive lamps almost always use a fourth property of the human body -- its capacitance. The word "capacitance" has as its root the word "capacity" -- capacitance is the capacity an object has to hold electrons. The lamp, when standing by itself on a table, has a certain capacitance. This means that if a circuit tried to charge the lamp with electrons, it would take a certain number to "fill it." When you touch the lamp, your body adds to its capacity. It takes more electrons to fill you and the lamp, and the circuit detects that difference. It is even possible to buy little plug-in boxes that can turn any lamp into a touch-sensitive lamp. They work on the same principle.

SOURCE: http://science.howstuffworks.com/innovation/science-questions/touch-sensitive-lamp.htm
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A lampshade is a fixture that covers the lightbulb on a lamp to diffuse the light it emits. Conical, cylindrical and other forms on floor-, desk- or table top-mounted as well as suspended lamp models are the most common and are made in a wide range of materials. The term can also apply to the glass hung under many designs of ceiling lamp. Beyond its practical purpose, significant emphasis is also usually given to decorative and aesthetic features.

History

In the late 17th-century in Paris the first public lanterns made their appearance in the centre of the streets. They lit the road during the night. In 1763, the réverbères made their appearance. These were oil lamps with reflectors which were hung above the center of streets. The first public oil lamps in Milan, financed by revenues from a lottery, date from 1785. These were lanterns containing an oil lamp with a number of wicks. A semi-spherical reflector above the flame projected the light downwards, while another reflector, slightly concave and near the flame, served to direct the light latterly.

Friedrich Albert Winsor first had the idea of industrializing lighting by producing gas in a factory and distributing it through a pipeline. In the first decades of the 19th century, competing gas companies laid the first gas mains in major cities. But there were fears of explosion and toxicity.

The flame fed by the gas coming out of the nozzle was intense, uniform and adjustable, white and brilliant instead of the reddish or orange of oil lamps or candles.

The drawbacks of gas lighting were overheating of the air and extremely high oxygen consumption, making it necessary to ventilate the room or isolate the flame by separating the room where the combustion took place from the room being lit. Theatre audiences regularly suffered from headaches and the sulphur and ammonia formed during combustion of the gas ruined furniture.

Gas light had to be filtered by opal glass or light fabric shades. Lampshades were no longer used to direct the light but to attenuate it.

In 1879, Joseph Swan and Thomas Edison independently developed—combining and perfecting existing elements deriving from the research of Humphry Davy, De Moleyn and Göbel—the incandescent filament electric light bulb.

To disguise the intense electric light, lampshades were used. Some were made by Tiffany in colored glass. The great advantage of the electric light bulb was the absence of flame and traces of combustion, thus avoiding all risks of intoxication, explosion or fire. In the beginning, the filament was made of carbonised vegetable fibres, then bamboo fibres and finally metal alloys until, in the early 20th century, the tungsten filament invented in 1904 became established.

Lampshade types

Modern lampshades can be classified by shape, by material, by fitter, or by function

Shades by shape

Lampshades are classified in four basic shapes: drum, empire, bell or coolie depending on their shape. Beyond the basics, lampshade shapes also include square, cut-corner, hexagon, gallery, oval, or scalloped shapes.

Lampshades by material

Lampshades are made of fabric, parchment, glass, Tiffany glass, or plastic. Common fabric materials include silk, linen, cotton, or even paper. Fabric shades are reinforced by metal frames to give the lampshades their shape, while paper shades can hold their shape without support. For this reason, paper shades can be more fragile than fabric shades. Darker shades sometimes add a reflective liner such as gold or silver in order to maximize light output.

Lampshade fitters

A "fitter" describes how the lampshade connects to the lamp base.

The most common lampshade fitter is a Spider fitter. Spider fitters are set on top of a lamp harp (A lamp harp is the component of a lamp to which the lamp shade is attached. It typically comes in two separate parts, a saddle which is fastened under the lamp socket, and the harp itself which consist of a lightweight frame attached to the saddle at its lower end and extending upwards to a point above the bulb. At the top of the harp is a threaded rod. The shade's internal frame (known as a spider) mounts on this rod and is secured in place by a lamp finial. Common materials for harps include brass and nickel. The most common thread size is 1/4-27),and secured with a finial (A finial or hip-knob is an element marking the top or end of some object, often formed to be a decorative feature. In architecture it is a decorative device, typically carved in stone, employed decoratively to emphasize the apex of a dome, spire, tower, roof, or gable or any of various distinctive ornaments at the top, end, or corner of a building or structure. Where there are several such elements they may be called pinnacles. Smaller finials in materials such as metal or wood are used as a decorative ornament on the tops or ends of poles or rods such as tent-poles or curtain rods or any object such as a piece of furniture. These are frequently seen on top of bed posts or clocks. Decorative finials are also commonly used to fasten lampshades, and as an ornamental element at the end of the handles of souvenir spoons. The charm at the end of a pull chain (such as for a ceiling fan or a lamp) is also known as a finial


Other fitters include clip-on (for either regular bulbs or candelabra bulbs), Uno, and notched-bowl fitter.



SOURCE: WIKIPEDIA 2017
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The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, horticulture, and other fields. In practice, color temperature is meaningful only for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e., those on a line from reddish/orange via yellow and more or less white to blueish white; it does not make sense to speak of the color temperature of, e.g., a green or a purple light. Color temperature is conventionally expressed in kelvins, using the symbol K, a unit of measure for absolute temperature.

Color temperatures over 5000 K are called "cool colors" (bluish white), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish white through red). "Warm" in this context is an analogy to radiated heat flux of traditional incandescent lighting rather than temperature. The spectral peak of warm-coloured light is closer to infrared, and most natural warm-coloured light sources emit significant infrared radiation. The fact that "warm" lighting in this sense actually has a "cooler" color temperature often leads to confusion.
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SATELLITE (coax) CABLE INFORMATION

What is the coaxial cable?

Coaxial cable, or coax (pronounced /ˈkoʊ.æks/), is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield.

Many coaxial cables also have an insulating outer sheath or jacket.

The term coaxial comes from the inner conductor and the outer shield sharing a geometric axis.

Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, who patented the design in 1880.

Coaxial cable differs from other shielded cable used for carrying lower-frequency signals, in that the dimensions of the cable are controlled to give a precise, constant conductor spacing, which is needed for it to function efficiently as a transmission line.

Applications

Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, digital audio (S/PDIF), and distributing cable television signals. One advantage of coaxial over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference.

Description

Coaxial cable conducts electrical signal using an inner conductor (usually a solid copper, stranded copper or copper plated steel wire) surrounded by an insulating layer and all enclosed by a shield, typically one to four layers of woven metallic braid and metallic tape. The cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor. The advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable. Larger diameter cables and cables with multiple shields have less leakage. This property makes coaxial cable a good choice for carrying weak signals that cannot tolerate interference from the environment or for stronger electrical signals that must not be allowed to radiate or couple into adjacent structures or circuits.

Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, and computer and instrumentation data connections.

The characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. A controlled cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum power transfer and minimum standing wave ratio. Other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield qualitY.

Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, and cost. The inner conductor might be solid or stranded; stranded is more flexible. To get better high-frequency performance, the inner conductor may be silver-plated. Copper-plated steel wire is often used as an inner conductor for cable used in the cable TV industry.

The insulator surrounding the inner conductor may be solid plastic, a foam plastic, or air with spacers supporting the inner wire. The properties of dielectric control some electrical properties of the cable. A common choice is a solid polyethylene (PE) insulator, used in lower-loss cables. Solid Teflon (PTFE) is also used as an insulator. Some coaxial lines use air (or some other gas) and have spacers to keep the inner conductor from touching the shield.

Many conventional coaxial cables use braided copper wire forming the shield. This allows the cable to be flexible, but it also means there are gaps in the shield layer, and the inner dimension of the shield varies slightly because the braid cannot be flat. Sometimes the braid is silver-plated. For better shield performance, some cables have a double-layer shield. The shield might be just two braids, but it is more common now to have a thin foil shield covered by a wire braid. Some cables may invest in more than two shield layers, such as “quad-shield”, which uses four alternating layers of foil and braid. Other shield designs sacrifice flexibility for better performance; some shields are a solid metal tube. Those cables cannot be bent sharply, as the shield will kink, causing losses in the cable.

For high-power radio-frequency transmission up to about 1 GHz, coaxial cable with a solid copper outer conductor is available in sizes of 0.25 inch upward. The outer conductor is rippled like a bellows to permit flexibility and the inner conductor is held in position by a plastic spiral to approximate an air dielectric.

Coaxial cables require an internal structure of an insulating (dielectric) material to maintain the spacing between the center conductor and shield. The dielectric losses increase in this order: Ideal dielectric (no loss), vacuum, air, polytetrafluoroethylene (PTFE), polyethylene foam, and solid polyethylene. A low relative permittivity allows for higher-frequency usage. An inhomogeneous dielectric needs to be compensated by a non-circular conductor to avoid current hot-spots.

While many cables have a solid dielectric, many others have a foam dielectric that contains as much air or other gas as possible to reduce the losses by allowing the use of a larger diameter center conductor. Foam coax will have about 15% less attenuation but some types of foam dielectric can absorb moisture—especially at its many surfaces — in humid environments, significantly increasing the loss. Supports shaped like stars or spokes are even better but more expensive and very susceptible to moisture infiltration. Still more expensive were the air-spaced coaxials used for some inter-city communications in the mid-20th century. The center conductor was suspended by polyethylene discs every few centimeters. In some low-loss coaxial cables such as the RG-62 type, the inner conductor is supported by a spiral strand of polyethylene, so that an air space exists between most of the conductor and the inside of the jacket. The lower dielectric constant of air allows for a greater inner diameter at the same impedance and a greater outer diameter at the same cutoff frequency, lowering ohmic losses. Inner conductors are sometimes silver-plated to smooth the surface and reduce losses due to skin effect. A rough surface prolongs the path for the current and concentrates the current at peaks and, thus, increases ohmic losses.

The insulating jacket can be made from many materials. A common choice is PVC, but some applications may require fire-resistant materials. Outdoor applications may require the jacket resist ultraviolet light, oxidation, rodent damage, or direct burial. Flooded coaxial cables use a water blocking gel to protect the cable from water infiltration through minor cuts in the jacket. For internal chassis connections the insulating jacket may be omitted.

SOURCED: WIKIPEDIA MARCH 2017
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STAY SAFE DURING THE DARKER NIGHTS – TIPS FROM IDEAL

HOME SECURITY: FLOOD LIGHTS WITH AND WITHOUT PIR, TIMERS AND LED LAMPS

Darker nights are here and it’s a good time to make sure your home is secure. You can do this by:

If you have an outdoor lamp already but it does not have a PIR (sensor to turn the lamp on and off), you can buy a separate PIR and have an electrician to install it allowing your lights to come on and off when someone approaches the house.
Install a floodlight which has a PIR and this will then come on and off as people approach your house.
Using a timer switch for lights. These are inexpensive, meaning homes are not left in darkness to alert burglars to an empty property
Using door and window locks, even when someone is home
Keeping your shed and garage locked – your tools could be used to break in to your house
Put your lights on a timer switch to make it look as though you are home.
LED Lights can be left on for longer periods of time (as they do not omit heat), so leave your lamp on.

TORCHES: ANY SHAPE OR SIZE WILL DO!

With the shorter days and the longer nights, most of us have no choice but to go out in the dark. Morning or evening, when the skies are dark and you’re digging for that last ounce of motivation to swap your cosy slippers for your trainers, to go shopping, take the dog for a walk or take out the recycling, the last thing you need to be contemplating is whether you’re going to feel safe enough to be out.

By keeping a torch handy, could make all of the difference. From pocket size to large rechargeable torches, they are a must in the dark winter nights.
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11/17/16
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