UL 60950 3rd Edition (formerly UL 1950, 3rd edition)
UL 60950 3rd Edition
(formerly UL 1950, 3rd edition)
After the divestiture of the AT&T/Bell system, the National Electric Code (NEC)
implemented Article 800-4, which mandates that “all equipment intended for connection to
the public telephone network be listed for that purpose” in order to ensure electrical safety.
A manufacturer can meet this requirement by listing their product with Underwriters
Laboratories under UL 60950 (based on IEC 60950, 3rd edition).
NEC requires all telecommunication wiring that enters a building to pass through a primary
protector, which is designed to limit AC transients in excess of 600 V rms. These transients
are due to the fact that telephone lines run in close proximity to AC power lines. Most
telecommunication equipment uses a secondary overvoltage protector such as the
SIDACtor device. The secondary devices typically limit transients in excess of 350 V rms.
Therefore, a potentially dangerous condition exists because of the voltage threshold
difference of the primary protector and the secondary protector. To minimize this danger,
compliance with UL 60950 overvoltage tests is required.
UL 60950 covers equipment with a rated voltage (primary power voltage) not exceeding
600 V and equipment designed to be installed in accordance with NEC NFPA 70. This
standard does not apply to air-conditioning equipment, fire detection equipment, power
supply systems, or transformers.
The effective date of UL 60950 allows new products submitted through April 1, 2003 to be
evaluated using the requirements of either UL 60950 or UL 1950, 3rd edition. After April 1,
2003, all new product submittals must be evaluated using only UL 60950.
Products certified by UL to requirements of UL 1459 prior to April 1, 2000 may continue to
be certified without further reinvestigation until April 1, 2005, provided no significant
changes or revisions are made to the products. Products certified by UL to requirements of
UL 1950 3rd edition prior to April 1, 2003 may continue to be certified without further
reinvestigation until April 1, 2005.
In order to have the UL Mark applied after April 1, 2005, all products, including those
previously certified by UL, must comply with UL 60950.
UL 69050 is intended to prevent injury or harm due to electrical shock, energy hazards, fire,
heat hazards, mechanical hazards, radiation hazards, and chemical hazards.
It defines three classes of equipment:
•
•
•
Class 1 — protection achieved by basic insulation
Class 2 — protection achieved by double or reinforced insulation
Class 3 — protection relying upon supply from SELV circuits (voltages up to 40 V peak
or 60 V dc)
UL 60950 also defines five categories of insulation:
•
•
•
•
•
Functional
Basic
Supplementary
Reinforced
Double
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SIDACtor Data Book and Design Guide
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