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24-399: Interlocks may include sophisticated elements such as curtains of infrared beams , photodetectors , simple switches , and locks . It can also be a computer containing an interlocking computer program with digital or analogue electronics. Trapped-key interlocking is a method of ensuring safety in industrial environments by forcing the operator through a predetermined sequence using

48-516: A mantrap . Interlocks can be used as a high level entrance security. There are two kinds of interlocking systems for security. The first form of interlocking security is more mechanical. For example, if an individual is entering a building, there may be two sets of doors to enter from. As the individual enters the first door, that door will close before they enter through the second door. This type of interlocking security can prevent piggybacking or tailgating . The second form of interlocking security

72-928: A Label Service for certain product categories that require more frequent inspections. Products that passed UL's testing and regular inspections were given a UL label, which eventually evolved into the UL Mark. From 1905 to 1979, UL Headquarters was located at 207-231 East Ohio Street in Chicago. In 1979, the organization moved its headquarters to a 153-acre campus in Northbrook, Illinois, 25 miles north of its former downtown Chicago location. UL Solutions has evolved from its roots in electrical and fire safety to address broader safety issues, such as hazardous substances, water quality, food safety, performance testing, safety and compliance education, and environmental sustainability . On January 1, 2012, Underwriters Laboratories became

96-439: A defined selection of keys, locks and switches. It is called trapped key as it works by releasing and trapping keys in a predetermined sequence. After the control or power has been isolated, a key is released that can be used to grant access to individual or multiple doors. Below is an example of what a trapped key interlock transfer block would look like. This is a part of a trapped key interlocking system. In order to obtain

120-662: A growing potential in this field, Merrill stayed in Chicago to found Underwriters Laboratories. He received initial funding from the Chicago Fire Underwriters' Association and the Western Insurance Union, a local insurance organization. With $ 350 of equipment, he opened a small laboratory on the third floor of a local fire insurance patrol station, signing UL's first test report on March 24, 1894. Merrill soon went to work on developing safety standards, conducting tests, and uncovering hazards. In

144-400: A lineman repairing the main feed far outside the building. An interlock device is designed to allow a generator to provide backup power in such a way that it (a) prevents main and generator power to be connected at the same time, and (b) allows circuit breakers to operate normally without interference in the event of an overload condition. Most interlock devices for electrical systems employ

168-552: A list of approved testing laboratories, which are known as Nationally Recognized Testing Laboratories . According to Lifehacker , UL Solutions is the best-known product safety and certification organization globally. Underwriters Laboratories Inc. was founded in 1894 by William Henry Merrill . After graduating from the Massachusetts Institute of Technology (MIT) with a degree in electrical engineering in 1889, Merrill went to work as an electrical inspector for

192-828: A mechanical device to manage the movement of circuit breakers. Some also allow for the use of padlocks to prevent someone from accidentally activating the main power system without authorization. Interlocks prevent injuries by preventing direct contact with energized parts of electrical equipment. Only qualified personnel, who must use a tool (such as a screwdriver), are allowed to bypass the interlock. Such interlocks are called defeatable interlocks , and are specified by Underwriters Laboratory (UL) standard UL508a, and National Electrical Code (NEC) Article 409.2. Defeatable interlocks are allowed on electrical equipment up to 600 volts. In high-security buildings, access control systems are sometimes set up so that ability to open one door requires another one to be closed first. Such setups are called

216-693: Is a global private safety company headquartered in Northbrook, Illinois , composed of three organizations, UL Research Institutes , UL Standards & Engagement and UL Solutions . Established in 1894, the UL enterprise was founded as the Underwriters' Electrical Bureau (a bureau of the National Board of Fire Underwriters ), and was known throughout the 20th century as Underwriters Laboratories . On January 1, 2012, Underwriters Laboratories became

240-404: Is an electric kiln. To prevent access to the inside of an electric kiln , a trapped key system may be used to interlock a disconnecting switch and the kiln door. While the switch is turned on, the key is held by the interlock attached to the disconnecting switch. To open the kiln door, the switch is first opened, which releases the key. The key can then be used to unlock the kiln door. While the key

264-420: Is electronic. This is in the form of detection and identification systems. Examples of such systems can be PIN codes, face recognition, and/or fingerprint recognition. In microprocessor architecture, an interlock is digital electronic circuitry that stalls a pipeline (inserts bubbles ) when a hazard is detected until the hazard is cleared. One example of a hazard is if a software program loads data from

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288-406: Is removed from the switch interlock, a plunger from the interlock mechanically prevents the switch from closing. Power cannot be re-applied to the kiln until the kiln door is locked, releasing the key, and the key is then returned to the disconnecting switch interlock. A similar two-part interlock system can be used anywhere it is necessary to ensure the energy supply to a machine is interrupted before

312-429: The keys in this system, a key must be inserted and turned (like the key at the bottom of the system of the picture). Once the key is turned, the operator may retrieve the remaining keys that will be used to open other doors. Once all keys are returned, then the operator will be allowed to take out the original key from the beginning. The key will not turn unless the remaining keys are put back in place. Another example

336-680: The system bus and calls for use of that data in the following cycle in a system in which loads take multiple cycles (a load-to-use hazard). An interlock may be used to prevent undesired states in a finite-state machine . Infrared beam Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.226 via cp1108 cp1108, Varnish XID 217688239 Upstream caches: cp1108 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 07:40:54 GMT Underwriters Laboratory The UL enterprise

360-655: The Boston Board of Fire Underwriters. At the turn of the twentieth century, fire loss was on the rise in the United States, and the increasing use of electricity in homes and businesses posed a serious threat to property and human life. In order to determine and mitigate risk, Merrill proposed to open a laboratory where he would use scientific principles to test products for fire and electrical safety. The Boston Board of Fire Underwriters turned this idea down, perhaps due to Merrill's youth and relative inexperience at

384-540: The company at about $ 7   billion. The company is listed on the New York Stock Exchange . The Recognized Component Mark is a type of safety certification mark issued by UL Solutions. It is placed on components which are intended to be part of a UL certified end product, but which cannot bear the full UL mark themselves. The general public does not ordinarily come across it, as it is borne on components which make up finished products. UL offers

408-476: The danger area by the stroke of the machine. A major problem in engineering operator safety is the tendency of operators to ignore safety precautions or even outright disabling forced interlocks due to work pressure and other factors. Therefore, such safeties require and perhaps must facilitate operator cooperation. Many people use generators to supplement power to a home or business in the event that main (municipal) power has gone offline. In order to safely transfer

432-602: The early years, UL tested three main types of products: devices meant to stop fire (such as fire extinguishers), devices meant to resist fire (such as fire doors), and devices that frequently caused fire (like wires used for electrical installations). This work soon expanded, and throughout the twentieth century, UL certified many pivotal consumer technologies, such as vacuum cleaners, televisions, microwaves, personal computers, and more. UL published its first standard, "Tin Clad Fire Doors", in 1903. In 1906, UL established

456-428: The front wheels of the car. In the operation of a device such as a press or cutter that is hand fed or the workpiece hand removed, the use of two buttons to actuate the device, one for each hand, greatly reduces the possibility of operation endangering the operator. No such system is fool-proof, and such systems are often augmented by the use of cable–pulled gloves worn by the operator; these are retracted away from

480-423: The machine is entered for adjustment or maintenance. Interlocks may be strictly mechanical. An example of a mechanical interlock is a steering wheel of a car. In modern days, most cars have an anti-theft feature that restricts the turning of the steering wheel if the key is not inserted in the ignition. This prevents an individual from pushing the car since the mechanical interlock restricts the directional motion of

504-537: The parent company of a for-profit company in the U.S named UL LLC, a limited liability corporation. The for-profit company took over the product testing and certification business. In 2022, the company revised their go-to-market strategy to include three separate organizations - UL Solutions, UL Standards & Engagement, and UL Research Institutes. UL Solutions became a public company via an initial public offering in April 2024 raising around $ 950   million, valuing

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528-450: The parent company of a for-profit company in the U.S. named UL LLC, a limited liability company , which took over the product testing and certification business. On June 26, 2022, the companies rebranded into three distinct organizations that make up the UL enterprise. The company is one of several companies approved to perform safety testing by the U.S. federal agency Occupational Safety and Health Administration (OSHA). OSHA maintains

552-414: The power source from a generator (and back to the main), a safety interlock is often employed. The interlock consists of one or more switches that prevent both main power and generator power from powering the dwelling simultaneously. Without this safeguard, both power sources running at once could cause an overload condition, or generator power back-feed onto the main could cause the dangerous voltage to reach

576-569: The time. In May 1893, Merrill moved to Chicago to work for the Chicago Fire Underwriters' Association. His task was to inspect the city's fire alarm systems. He was also sent to the 1893 World's Fair to inspect the Fair's electrical installations and the Palace of Electricity. In order to determine and mitigate risk in his role as an electrical inspector, Merrill found it necessary to conduct tests on building materials and electrical components. Upon seeing

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