August 1955 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
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
Board of Fire Underwriters (later changed to American Insurance Association,
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. 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. 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. Temperatures of various parts as well as operation
of the thermostat are also checked.
By 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
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
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.
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.
Posted March 2, 2021
(updated from original post on 8/26/2011)