Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives Magazine Sponsor RF Cafe Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Alliance Test Equipment Centric RF Empower RF ISOTEC Reactel RF Connector Technology San Francisco Circuits Anritsu Amplifier Solutions Anatech Electronics Axiom Test Equipment Conduct RF Copper Mountain Technologies Exodus Advanced Communications Innovative Power Products KR Filters LadyBug Technologies Rigol TotalTemp Technologies Werbel Microwave Windfreak Technologies Wireless Telecom Group Withwave RF Cafe Software Resources Vintage Magazines RF Cafe Software WhoIs entry for RF Cafe.com Thank you for visiting RF Cafe!
everythingRF RF & Microwave Parts Database (h1)

Windfreak Technologies Frequency Synthesizers - RF Cafe

Anatech Electronics RF Microwave Filters - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel

LadyBug LB5954L Power Sensor with LAN Option - RF Cafe

Behind the U.L. Label
August 1955 Popular Electronics

August 1955 Popular Electronics

August 1955 Popular Electronics Cover - RF CafeTable of Contents

Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

The Underwriter's Laboratory (UL) is an entity that seems to have been around forever. A lot of people - maybe most people - assume that it is a government entity. In fact, it is a non-profit organization sponsored by the National Board of Fire Underwriters (later changed to American Insurance Association, then to APCIA). Its roots are traceable back to the Chicago World's Fair in 1893. Concern over the potential fire hazard of Edison's light bulbs was the impetus for the effort. Another aspect of the UL that a lot of people don't know is that the UL label of approval is no guarantee that the device works properly, only that it passes standards of safety as it relates to fire hazards. This article in the August 1955 edition of Popular Electronics magazine gives a brief history.

Behind the U.L. Label

Television sets are subjected to a thorough going-over by Underwriters' Laboratories - RF Cafe

Television sets are subjected to a thorough going-over by Underwriters' Laboratories. Inc. engineers. Special attention is paid to shock hazards and to overheating problems. Cabinets are pounded and safety glass hit with steel balls in test. 

An enclosed heavy-duty switch is tested in one of U.L.'s many laboratories - RF Cafe

An enclosed heavy-duty switch is tested in one of U.L.'s many laboratories. Equipment such as this is operated repeatedly under excessive loads before it is approved and given the U.L. label. It is important to point out that U. L. approval does not guarantee quality of performance. The testing is concerned primarily with the safety aspects of equipment. Thus, the label on an approved radio receiver, for instance, does not imply that it will perform better than one not so approved. It does mean, though, that the chance of setting a house on fire is negligible if the approved model is used. 

Automatic flatiron is dropped four times during continuous operation test of 500 hours - RF Cafe

Automatic flatiron is dropped four times during continuous operation test of 500 hours. Temperatures of various parts as well as operation of the thermostat are also checked.

These are only a few of the authorized labels used by U.L. to designate approved equipment - RF Cafe

 These are only a few of the authorized labels used by U.L. to designate approved equipment. An item bearing such a label has met specifications and passed severe tests.

Behind the U.L. Label - RF CafeBy E. D. Morgan

Equipment is tested, dropped, pounded, and burned before it is rated as safe and tagged with the Underwriters' okay.

A familiar sight on much electrical and electronic equipment used today is an Underwriters' Laboratories label. Exactly what is implied by the use of this label, however, is often misunderstood.

Underwriters' Laboratories, Inc. is a non-profit organization sponsored by the National Board of Fire Underwriters. Its function is to test and inspect materials and equipment to prevent loss of life and property from fire, crime and casualty hazards. To do this adequately, it subjects devices to grueling tests. Only the hardiest designs survive and earn the right to the coveted label of acceptance.

No conceivable method of testing is overlooked. Much of the test equipment is of U. L.'s own design and they dream up diabolical plans to subject samples to the meanest treatment possible. They try to anticipate all of the mistakes that could be made by a consumer. Appliances are left on for weeks and electric heater cords are twisted and untwisted thousands of times.

Television cabinets get a thorough pounding before they receive U. L. approval. A large picture tube can be a deadly weapon when broken, as it hurls tiny fragments of glass in all directions. To insure against injury, the safety screen on the front must be capable of withstanding such shattering. A pound-and-a-quarter steel ball is hurled at the set to determine its fitness for this purpose.

Electronic equipment is often used by U.L. technicians. Here, the split-second operation of a burglary detection system is photographed. Accuracy is assured by using a cathode-ray oscilloscope, a beat-frequency generator, and various meters.

To determine whether a safe is fire-proof and burglar-proof, U. L. employs its own staff of "arsonists" and "safecrackers." These men are masters at their trades and tackle a new item with drills, sledges, torches, and explosives. Just to make sure, the safes are dropped onto concrete from a second-story level, then placed in a 2000 °F furnace for an hour or so. If the internal temperature goes high enough to turn valuable papers brown, what is left of the safe is returned to the maker with regrets.

Fire doors are tested in large gas furnaces where flames lick at them until they are red-hot. Then a fire hose is intermittently played on the other side of the door. Acceptable fire barriers must pass the fire endurance as well as the hose stream tests.

U. L.'s Growth

The organization had its unique start when bulbs were installed at the first Chicago World's Fair in 1893. These became the Fair's chief attraction - as well as its greatest hazard. Fires, started by the not-yet-perfected lamps and wiring, were commonplace. This led a group of New England insurance interests to authorize William H. Merrill, a young engineer, to investigate the situation. He responded to each fire alarm at the fairgrounds. If the cause were electrical, he would try to locate the defective device and determine why it failed.

Because of Merrill's insistence on thorough testing before the lamps were installed, and correcting their faults before offering them to the public, Underwriters' Laboratories, Inc. was born the following year. Merrill was its first president.

Since then, U. L. has mushroomed. Over 375,000 products have been found acceptable under its rigorous standards. Testing laboratories are located in Chicago, New York and San Francisco, with representatives in nearly 200 cities insuring that the standards are upheld at the factories. The work is financed solely by charges made to manufacturers for the inspection of their equipment.

Annual lists are published giving the manufacturers' names and their approved products. Four main lists are prepared which cover: electrical equipment; fire protection equipment; gas, oil and miscellaneous appliances; and accident hazard, automotive equipment and burglary protection.

Good will and impeccable honesty is the main stock-in-trade of this organization. U. L. never solicits business, but industry has learned that it is well worth the effort to make sure its products deserve the U. L. label.



Posted March 2, 2021
(updated from original post on 8/26/2011)

LadyBug LB5954L Power Sensor with LAN Option - RF Cafe
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe

ConductRF Phased Matched RF Cables - RF Cafe

PCB Directory (Manufacturers)