Terms & Acronyms
Brush up on conversion basics, familiarize yourself with switch terms and acronyms, and discover more about lamps and LEDs, processing and electrical ratings, and materials associated with the NKK product line.
A
ABS
Acrylonitrile Butadiene Styrene; a thermoplastic composed of styrene and acrylic resin which provides shatterproofing and a shiny appearance; it is resilient and can be easily metal plated.
AC
Alternating Current; electric current that continually reverses direction at a fixed frequency.
alloy
a metal created by combining two or more different metals to obtain a desired physical property.
alternate action
commonly describing pushbutton switches; remaining in a given circuit condition after removal of actuating force; when actuating force is applied a second time, the opposite circuit is engaged; also known as push-push switching action; may or may not be latchdown.
ambient temperature
operating temperature range.
angle of throw
used with rockers and toggles to indicate total travel arc measured in degrees.
annealed
relieved of mechanical stress through the application of heat and gradual cooling; for example, annealed copper is less brittle.
ANSI
American National Standards Institute; a standard-setting agency of the United States which approves the design and/or performance of electrical/electronic components that are distributed in the world market.
arcing
the flow of electric current between opening or closing switch contacts.
B
bifurcated
contact a two-pronged, wiping movable contact.
bounce
the repeated rebounding of the movable contact during the transfer from one throw to the next; measured in milliseconds.
brass
an alloy of zinc and copper.
break before make
interrupting one circuit of a pole before completing another of the same pole (nonshorting contact).
C
capacitive load
a load in which the initial current on make is higher than steady state; upon break it is less than steady state. Current leads voltage in capacitive loads.
clad
the joining of two dissimilar materials by welding or bonding.
contact resistance
the resistance across a pair of closed contacts which is in series with the load; this resistance increases with the age of the switch at a rate varied by environment, frequence of use, voltage, and load conditions; measured in milliohms.
creepage
the unwanted flow of electrical current from one conductive part to another.
CSA
Canadian Standards Association.
cycle
the complete sequence of indexing through all successive switch positions and returning to the original position.
D
DC
Direct Current; electric current that flows only in one direction.
detent
a mechanical positioning device for stopping actuator travel at each successive electrical circuit; for example, a spring-operated ball and groove.
dielectric strength
the ability of an insulating material to withstand high voltage without electrical degradation.
differential travel
the distance an actuator moves between the point where contacts snap over and where they snap back, or where a contact makes and then breaks.
DIP
Dual Inline Package, indicating .100" center-to-center terminal spacing and .300" row-to-row spacing.
double break
having two pairs of contacts (shorting bar) that open the circuit at two places; having this added contact material improves heat dissipation and increases life; desirable in DC circuit applications.
DP
Double Pole; see pole.
dry circuit
a low energy circuit condition where no arcing occurs during contact switching; for example 0.4VA maximum @ 28V AC/DC maximum; see logic level.
DSP
National Defense Standards of Japan; NKK file numbers C 6310B & C 6313.
DT
Double Throw; see throw.
F
flash plating
a very thin or "instant plating" of usually less than 10 microinches in thickness.
flux
chemical used for cleaning metal surfaces so that solder will flow out on the metal; fluxes change a passive, contaminated metal surface into an active, clean, solderable surface.
G
gull wing
a type of surface mount terminal which extends from the side of the switch and has an L-shaped bend at the end.
I
inductive load
a load in which the initial current on make is lower than steady state and upon break is greater than steady state. The long arcing time, due to stored energy in the inductor at the time of breaking, is severe on the switch contacts.
IEC
International Electrotechnical Commission
3 Rue de Varembe
P. O. Box 131
1211 Geneva 20, Switzerland
IECQ
IEC's Quality Assessment System for Electronic Components, created in 1983 to facilitate national and international trade in certified electronic components; a worldwide certification system which provides a method whereby electronic components made and handled by approved manufacturers and distributors can be used anywhere without further testing.
infrared reflow
a method of mass soldering surface mount devices with some form of infrared (IR) thermal radiation, such as a lamp IR system where PCB and components are heated largely by radiant energy from IR lamps.
inrush
the initial, transitory high-level of current through contacts upon making (closing); can cause severe degradation of contacts; applicable to resistive and capacitive loads.
IP
part of the IEC529 standard recommending the degree of protection of enclosures for low- voltage switch gear; specifically, concerned with protection of persons against contact with live or moving parts and the prevention of ingress of solid foreign bodies and liquid; an industrial specification used internationally and similar to NEMA.
insulation resistance
the electrical resistance between two normally insulated parts; measured at a specific high potential; usually greater than 1 megohm.
isolated lamp circuit
independent of switching circuit; lamp is operated on a circuit separate from the switch circuit.
J
JETL
Japan Electrical Testing Laboratory.
JIS
Japan Industrial Standard; Japan Industrial Standards Committee (JISC) Agency of Industrial Science and Technology.
L
lamp load (tungsten)
most notably characterized by the high inrush current at make (approximately 10 to 16 times the steady state).
latchdown
one type of alternate action in which the pushbutton is mechanically fastened in the down position; the pushbutton is at "normal" position for one circuit and latched down position for the other circuit condition.
LED
Light Emitting Diode; provides illumination with advantages of long life and low power consumption.
logic level
an application in which power levels do not cause arcing, melting, or softening of contacts; also referred to as dry circuit or low energy; specificied 0.4VA max @ 28V AC/DC max; typically requiring gold contacts for reliability.
M
maintained action
remaining in a given circuit condition until actuated to the opposite circuit condition where it is again maintained; opposite momentary action.
make before break
completing one circuit of a pole before interrupting another of the same pole (shorting contact).
MITI
Ministry of Industry & Trade Institute (Japan).
momentary action
mechanically returning from a temporary circuit condition to the normal circuit condition as soon as the actuating force is removed.
MSCP
Mean Spherical Candle Power; a unit of measure of light intensity.
N
NBR
Nitrile Butadiene Rubber, a copolymerization of nitrile and butadiene which is used mainly to meet oilproof requirements of o-rings and switch boots or covers.
NC
Normally Closed contacts; circuit is closed when actuator is in relaxed or normal position.
NEMA
National Electrical Manufacturers Association, an agency of the United States setting standards for products distributed worldwide; applied to switches in their degrees of protection against the intrusion of liquids, dust, and other contaminants.
Newton
the unit of measure for operating force abbreviated N; see the conversion tables in the previous subsection.
NO
Normally Open contacts; circuit is open when actuator is in relaxed or normal position; applies to momentary or alternate action switches.
nominal
the result of the calculated actual value range.
nonshorting contacts
contacts which break before make.
nonswitching rating
the power carrying capability of a switch after contact closure and at the end of contact bounce; usually much higher than the switching rating.
O
opaque
condition that prevents the passage of light.
overtravel
the distance an actuator moves beyond the point at which electrical contacts transfer.
P
panel seal
liquid is prevented from reaching the switch contacts from the front of the panel if the panel is subjected to spills or splashing.
PBT
polybutylene terephthalate, a polyester thermoplastic resin compound.
PCB
Printed Circuit Board; thin copper traces on a plastic laminate providing low cost, low current mass wiring.
PF
Power Factor; a means of determining contact capability when used with inductive loads relative to the standard resistive load rating; for example, if PF = 1.0 the inductive load is 100% of the resistive load, or if PF = 0.6 the inductive load is 60% of the resistive load.
pole
a single common electrical input having one or more outputs.
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| Single Pole (w/1 output) | Single Pole (w/12 outputs) | Double Pole (w/2 outputs) |
position
the mechanical detents of a switch actuator.
PPS
polyphenylene sulfide; a thermoplastic resin which is chemical and flame resistant.
pretravel
the distance an actuator moves before a change in the electrical condition is made.
push-push
also known as alternate action; is not latchdown.
R
Reliability Center for Electronic Components of Japan, member of EXACT (International Exchange of Authenticated Electronic Component Performance Test Data).
resistive load
the easiest load to switch because current and voltage are in a steady state on make and drop instantly to zero on break; produces minimal arcing which maximizes contact life.
RMS
Root Mean Square.
S
SEMKO
Svenska Elektriska Materielkontrollanstalten of Sweden.
SEV
Schweizerischer Elektrotechnischer Verein of Switzerland.
shorting contacts
contacts which make before break.
silicone rubber
rubber made from silicone elastomers and noted for its retention of flexibility, resilience, and tensile strength over a wide temperature range.
SIP
Single Inline Package, indicating .100" center-to-center terminal spacing with terminals aligned in one row.
snap action
the abrupt transfer of contacts from one position to another; this action is relatively independent of the speed of actuator travel.
SPST
Single Pole Single Throw; see pole, also throw.
STC
Sliding Twin Contact, an NKK-patented mechanism with two movable contact surfaces which pinch the stationary contacts.
surface mount
component terminals are soldered to pads on the surface of the PC boards as opposed to using holes for mounting; terminal shapes vary -- gull wing, J-bend, and others.
synchronous lamp circuit
lamp is operated on a circuit in phase with the switch; the switch contains a separate circuit to open or close the lamp circuit simultaneously with the switching circuit.
T
tactile feedback
the switching action felt by an operator.
thermal shock
the state of a component that is undergoing an excessive temperature change, particularly in reference to movement from one process to another in soldering and cleaning.
throw
the number of electrical circuits within a pole.
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| ingle Throw (w/2 poles) | Double Throw (w/1 pole) | Three Throw (w/4 poles) |
total travel
sum of pretravel and overtravel; full distance an actuator moves from relaxed position past the point of electrical contact and to the end of travel.
translucent
transmitting and diffusing light so that objects beyond cannot be seen clearly.
transparent
transmitting light without appreciably scattering so that objects lying beyond are entirely visible.
travel
the distance the actuator moves to effect the change of electrical circuits; see also differential travel, pretravel, overtravel, and total travel.
two circuit
circuit in which one circuit is completed in one position and another separate circuit is completed in the other position.
U
UL
Underwriters Laboratories Inc.; many of NKK's switches are UL Recognized.
undercoating
a coating used for preparation of a surface for plating or used to prevent corrosion when the finish plating develops pinholes; thickness of an undercoating is determined by its purpose.
V
vapor phase
a process well-suited to soldering surface mount devices; it combines infrared preheating with condensation heating for reflow, advantageous for eliminating overheating of components and PCB.
VDE
Verband Deutscher Elektrotechniker of Germany.
W
washable
capable of being subjected to automated washing procedures after wave soldering without diminishing electrical or mechanical life specifications; see "Washability Data" in the Supplement; other terms such as process compatible, totally sealed, and immersible are sometimes used to describe washability.
wave soldering
a method of soldering in which a wave of molten solder contacts surfaces as the PC board with components is conveyed through the process; wave width, travel speed, dwell time, etc. are varied to achieve desired results.
wiping action
sliding of contacts over one another resulting in cleaning of the surfaces