Cut Sheet

Switches
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Single Pole (SP): A switch device that opens,
closes or changes connections in a single
conductor of an electrical circuit
Double Pole (DP): A switch device that
opens, closes or changes connections in both
conductors of the same circuit.
Two Circuit (2 CIR): A switch device that
opens, closes or changes connections in a single
conductor of two independent circuits.
Single Throw (ST): A switch device that
opens, closes or completes a circuit at only one
of the extreme positions of its actuator.
Double Throw (DT): A switch device that
opens, closes or completes a circuit at both
extreme positions of its actuator.
Actuator: A lever, push-button, slide, trigger
or other means by which an external force is
applied to operate a switch mechanism.
Normally Open (NO): A momentary type
switch in which one or more circuits are open
when the switch actuator is at its normal
or rest position.
Normally Closed (NC): A momentary type
switch in which one or more circuits are closed
when the switch actuator is at its normal or
rest position.
Alternate Action (Double Action Push):
Push to make, then push to break, a circuit.
Power Ratings for Switches: The current
handling capability of a switch measured
in amperes, horsepower, lamp load or
combinations of these with applicable voltages.
Switch Terminology
UL/CSA Rated Switches
A UL/CSA-marked rating in amperes
indicates that the switch meets or exceeds
test house performance requirements of 6000
make-and-break cycles at the rated current,
preceded by 50 make-and-break cycles at 150%
switch current rating. 125% is used when switch
ratings exceed 10 amperes.
A UL/CSA horsepower-only rated device
meets minimum test requirements of 50
make-and-break cycles at the appropriate
locked rotor current, followed by 6000 cycles
at one-sixth the AC-locked rotor current and
10% of the DC-locked rotor current.
AC ampere ratings are resistive or inductive,
with the inductive rating tested at 75% to 80%
power factor.
AC horsepower ratings are inductive and tested
at 40% to 50% power factor.
“L” Rating denotes ability of an AC-only switch
to handle the initial high in-rush characteristics of
a tungsten filament lamp on AC voltage only.
“T” Rating denotes ability of an AC/DC switch to
handle the initial high in-rush characteristics
of a tungsten filament lamp on either AC or
DC voltage.
All DC ratings are 100% resistive only
(non-inductive).
Many AC-only rated switches can be used
in applications where less than 30 volts DC is
required, provided current does not exceed full
current rating of the switch.
Ampere-rated switches will not automatically
handle in-rush characteristics of five to six times
switch rating.