|Names||Underwriter's knot, Two-strand wall knot|
|Related||wall knot, crown knot|
|Caveat||Note that the colors in this depiction do not match current practises in either the UK or the US, nor is this cable in keeping with current safety standards for electrical installations|
The underwriter's knot is used in electrical wiring as strain relief to prevent a cable from being pulled from electrical terminals when the cable is yanked.
Clifford Ashley listed it as an electrician's knot in 1944. He suggested it be used "where rough treatment is expected" and described it as a two-strand wall knot.
The name may come from its use by fire underwriters, who understood its importance in electrocution and fire prevention.
The knot is typically used as a stopper knot where a lamp or appliance cord passes through a hole or slot of a plug or socket. Its purpose is to "reduce strain on the screw terminal connections—where the metal parts of the wires connect to the socket or plug—and prevent the wires from pulling free."
A whipping knot or whipping is a binding of marline twine or whipcord around the end of a rope to prevent its natural tendency to fray.
Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between parts of an electrical circuit, or between different electrical circuits, thereby joining them into a larger circuit. Most electrical connectors have a gender – i.e. the male component, called a plug, connects to the female component, or socket. The connection may be removable, require a tool for assembly and removal, or serve as a permanent electrical joint between two points. An adapter can be used to join dissimilar connectors.
A grief knot is a knot which combines the features of a granny knot and a thief knot, producing a result which is not generally useful for working purposes. The word grief does not carry its usual meaning but is a portmanteau of granny and thief.
A power cord, line cord, or mains cable is an electrical cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line voltage. The terms power cable, mains lead, flex or kettle lead are also used. A lamp cord is a light-weight, ungrounded, single-insulated two-wire cord used for small loads such as a table or floor lamp.
A grommet is a ring or edge strip inserted into a hole through thin material, typically a sheet of textile fabric, sheet metal or composite of carbon fiber, wood or honeycomb. Grommets are generally flared or collared on each side to keep them in place, and are often made of metal, plastic, or rubber. They may be used to prevent tearing or abrasion of the pierced material or protection from abrasion of the insulation on the wire, cable, line being routed through the penetration, and to cover sharp edges of the piercing, or all of the above.
A power strip is a block of electrical sockets that attaches to the end of a flexible cable, allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often used when many electrical devices are in proximity, such as for audio, video, computer systems, appliances, power tools, and lighting. Power strips often include a circuit breaker to interrupt the electric current in case of an overload or a short circuit. Some power strips provide protection against electrical power surges. Typical housing styles include strip, rack-mount, under-monitor and direct plug-in.
Electrical wiring in North America follows the regulations and standards applicable at the installation location. It is also designed to provide proper function, and is also influenced by history and traditions of the location installation.
A stopper knot is a knot that creates a fixed thicker point on an otherwise-uniform thickness rope for the purpose of preventing the rope, at that point, from slipping through a narrow passage, such as a hole in a block. To pass a rope through a block, or hole, is to reeve it. To pull it out is to unreeve it. Stopper knots prevent the rope from unreeving on its own.
Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
An extension cord (US), power extender, drop cord, or extension lead (UK) is a length of flexible electrical power cable (flex) with a plug on one end and one or more sockets on the other end. The term usually refers to mains extensions but is also used to refer to extensions for other types of cabling. If the plug and power outlet are of different types, the term "adapter cord" may be used. Most extension cords range from around two to thirty feet in length although they are made up to 300 feet in length.
A cable tie is a type of fastener for holding items together, primarily electrical cables and wires. Because of their low cost, ease of use, and binding strength, cable ties are ubiquitous, finding use in a wide range of other applications. Cable ties were first manufactured by Thomas & Betts under the brand name Ty-Rap.
Knob-and-tube wiring is an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s. It consisted of single-insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installations were twisted together for good mechanical strength, then soldered and wrapped with rubber insulating tape and friction tape, or made inside metal junction boxes.
A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets.
British telephone sockets were introduced in their current plug and socket form on 19 November 1981 by British Telecom to allow subscribers to connect their own telephones. The connectors are specified in British Standard BS 6312. Electrical characteristics of the telephone interface are specified by individual network operators, e.g. in British Telecom's SIN 351. Electrical characteristics required of British telephones used to be specified in BS 6305.
Cable management refers to management of electrical or optical cable in a cabinet or an installation. The term is used for products, workmanship or planning. Cables can easily become tangled, making them difficult to work with, sometimes resulting in devices accidentally becoming unplugged as one attempts to move a cable. Such cases are known as "cable spaghetti", any kind of problem diagnosis and future updates to such enclosures could be very difficult.
A coiling or coil is a curve, helix, or spiral used for storing rope or cable in compact and reliable yet easily attainable form. They are often discussed with knots.
Rope are often coiled and hung up in lofts for storage. They are also hung over stakes in farm wagons and on hooks in moving vans, fire apparatus and linesmen's repair trucks. For such active storage coils must be well made.
MC4 connectors are single-contact electrical connectors commonly used for connecting solar panels. The MC in MC4 stands for the manufacturer Multi-Contact and the 4 for the 4 mm diameter contact pin. MC4s allow strings of panels to be easily constructed by pushing the connectors from adjacent panels together by hand, but require a tool to disconnect them to ensure they do not accidentally disconnect when the cables are pulled. The MC4 and compatible products are universal in the solar market today, equipping almost all solar panels produced since about 2011. Originally rated for 600 V, newer versions are rated at 1500 V, which allows longer strings to be created.
Solarlok is a largely obsolete electrical connector used to connect solar panels together. Solarlok was introduced by Tyco International in order to meet new National Electrical Code (NEC) standards that required panel connectors to lock together and only be separated again using a tool. Solarlok became very common in the United States where the code first came into effect, but had varying degrees of market success outside the US. Due to the connector only being available from Tyco, the connectors are almost always referred to simply as Tyco connectors.
Hubbell Incorporated is an American company that designs, manufactures and sells electrical and electronic products for non-residential and residential construction, industrial and utility applications. Hubbell was founded by Harvey Hubbell as a proprietorship in 1888, and was incorporated in Connecticut in 1905. It is ranked 602 by Fortune. The company’s reporting segments consist of the electrical segment and the Power segment. Hubbell’s manufacturing facilities are located in the United States, Canada, Switzerland, Puerto Rico, Mexico, the People's Republic of China ("China"), Italy, the United Kingdom, Brazil and Australia and maintains sales offices in Singapore, China, India, Mexico, South Korea, and countries in the Middle East. Hubbell was previously headquartered in Orange, Connecticut, and has now moved its headquarters to Shelton, Connecticut. Hubbell Inc. assisted Allied efforts during World War II by manufacturing military vehicle electrical circuits, battery-charging systems for M4 Sherman tanks, power jacks for test meters, vacuum tube sockets for radio communications, and a line of electrical and electronic connectors for aircraft. Hubbell Inc is in List of S&P 400 companies having stocks that are included in the S&P 400 stock market index, maintained by S&P Dow Jones Indices.
A towing sock or wire rope puller is a device that connects to the end of a cable, such as a power cable, in order to pull it through a tube or tunnel. It works by tightening around the cable when pulled, in the same manner as a Chinese finger trap. The towing sock is tubular and made of braided cable, open at one end and closed at the other where it connects to a tow line using an eye splice.