Switch construction

ACTUATOR : A movable part of a switch which causes a change in the electrical configuration of the switch. e.g. : Toggle, Rocker, Slider, Paddle, Pushbuttons, Shaft

ALLOY : A metal created by combining two or more metals to obtain a specific physical property

ALTERNATE ACTION
: Push to close and push to open the switch. A given circuit condition remains after removal of actuating force. Also known as "push-push switching action". Typically, alternate action pushbuttons do not visually indicate the position of the contacts. Contrast to latching action.

ANGLE OF THROW
: Indicates total travel arc on toggle or rocker switches. Unit of measure : degrees

BIFURCATED CONTACT : A wiping movable contact consisting of spring fingers that grip fixed contacts. Typically found in slide switches. Self cleaning action. See Wiping Contact.

BRASS : An alloy of zinc and copper

BREAK-BEFORE-MAKE (Non shorting - B.B.M.) : On actuation, the movable contact breaks contact with one fixed contact before making contact with another fixed contact. Contrast with make-before break. Typical of toggle and pushbutton switches.

BUTT CONTACT
: A contact mechanism in which the movable contact makes contact with the fixed (stationary) contact without wiping motion between the surfaces. Typical of toggle and pushbutton switches. See Wiping Contact.

CLEARANCE (spacing) : Distance through air between electrically live parts of opposite polarity or to ground.

CONTACT (Contact area) : The metal surfaces that come into physical contact to complete an electrical circuit. These surfaces are found on movable contacts (see) and terminals (see).

CONTACT BLOCK : A switching element which is added singly or in groups to an operator to make a complete switch. Typically used with industrial controls (APEM A01 and A02 series).

CONTACT GAP : The distance between a stationary contact and a movable contact in the open position.

DETENT : A mechanical stop that holds the contacts in a given position after the actuation force is removed or prevents the changing of contact position at less than a specified actuation force. Can also be referred to as tactile feel.

DIFFERENTIAL TRAVEL : The distance an actuator moves between the point where contacts snap over and where they snap back, or when contact is made and then brakes.

DIP : DIP-in-line Package (in Europe also, DIL : Dual-in-line) refers to a component with two rows of PC terminals. The terminals are most commonly on a 0,100" pitch with 0,300" between rows.

DOUBLE-BREAK CONTACTS
: A contact mechanism using two sets of contacts to make or break a given circuit. The contact gap opens twice as fast, reducing the arc duration, contact surface temperature and material erosion. This improves heat dissipation and provides better power handling capacity for a longer switch life. Typical of high power industrial switches and DC Circuit application. See Single-Break Contacts.

DP : Double pole. See pole.

DT : Double Throw. See Throw.

DUST TIGHT : Sealed switch will withstand sand and dust contamination.

ENVIRONMENTAL SEAL : A seal that totally encapsulates the switch providing a specified level of protection against intrusion of solids, liquids or gases into the body of the device.

FIXED CONTACT (Stationary contact) : The non-moving contact. Typically integral to the end of the terminal inside the switch body.

FLASH PLATING : A very thin or "instant" plating (usually less than 0.25 microns in thickness).

GOLD FLASH : A plating of gold typically less than 10 micro-inches (milliononths) thick. Used only as a barrier to oxidation or corrosion of terminals to maintain solderability.

GULL WING : A type of surface mount terminal which extends from the side of the switch and has a L-shaped bend at its end (terminals are formed away from the switch body).

INSERT MOLD : In switches and relays used to refer to terminations that are placed in the mold so that plastic is molded around the terminations. The chief benefit is an inherent seal against the intrusion of flux into the body of the device. Therefore no epoxy terminal seal is required.

LATCHING ACTION : See alternate action (or push-push). Actuator position typically indicates contact position.

LEAKAGE BARRIER
: A ridge or web molded into a switch housing between terminals or contacts to increase the surface distance between them.

LED : Light Emitting Diode. Long life and low consumption illumination

MAINTAINED : A position of a switch which remains unchanged when actuation force is removed from switch actuator. Contrast with Momentary.

MAKE-BEFORE-BREAK (shorting, MBB) : Movable contacts make the next circuit before breaking the first circuit. Typically found in slide switches. Contrast with Breakbefore-make.

MAKE AND BREAK : Opening one circuit before completing another on the same pole

MOMENTARY ACTION : Mechanically returning from a temporary switch position to the normal switch position

MOMENTARY ACTION : Mechanically returning from a temporary switch position to the normal switch position

NC : See Normally Closed

NO : See Normally Open.

NON-SHORTING : See Break-Before-Make

NORMALLY CLOSED (NC) : Normally closed contacts are closed when the switch actuator is in its unactuated position (e.g., the plunger is in the resting position in the case of a pushbutton switch).

NORMALLY OPEN (NO) : Normally open contacts are open when the switch actuator is in its unactuated or resting position.

OIL-TIGHT : A generic term for a panel seal (see) commonly used in industrial settings. Defined by NEMA (see) standard.

OPEN FRAME : Typical to slide switches ; open frame construction allows for automatic solder process and post solder cleaning. Contrast with "washable".

OPERATOR : A panel-mounted mechanical device (pushbutton, selector, keylock, etc.) without contacts to which one or more contact blocks may be added to make a complete switch (See APEM A01-A02 Series).

OVERTRAVEL : The distance the actuator may move between initial electrical contact position and the extreme mechanical position of the actuator. See Travel, Pretravel.

PANEL SEAL : A panel seal provides a defined level of protection against penetration of liquids through the switch and switch-to-panel interface to the rear of a panel.

POLE : Single common electrical input having one or more outputs. The number of seperate circuits that can be active through a switch at any one time. A single-pole switch allows one closed circuit at a time. A double-pole switch allows two closed circuits, etc.

PRETRAVEL : The distance the actuator moves from a rest position (or free position) to electrical make at another position. See Travel, Overtravel.

PUSH-ON / PUSH-OFF : See Alternate Action.

PUSH-PUSH : See Alternate Action.

QUICK-CONNECT TERMINAL : Flat tab or blade style terminals designed to accept push-on female wire connectors (instead of soldering). The most popular sizes are : 0.250". 0.187". 0.110" wide.

SHORTING CONTACT : Contacts which make-before-break. See Make-before-Break

SILICON RUBBER : Rubber made from silicone elastomers which keeps its high level of flexibility, resilience and tensile strength over a wide temperature range.

SINGLE BREAK CONTACTS : A contact mechanism using one set of contacts to make or break a given circuit. Typical of electronic or low power switches. See Double-Break Contacts.

SNAP ACTION : The fast transfer of contacts from one position to another, this action is rather independent of the speed of actuator travel

SPACING : See Clearance

SPDT : Single pole double throw. See Pole, See Throw.

SPLASHPROOF : Sealed switch will withstand heavy rain or stream of water. See Panel Seal.

SPRING RETURN
: See momentary.

TERMINAL : The metal portion of a switch, exterior to the body, that is used to connect the switch to an electrical circuit. Example : PC, wire lug, quick-connect, wirewrap,
etc.

THROW : The number of circuits that can be controlled by any one pole of a switch. Example : In a single-pole-double-throw (SPDT) switch, only one circuit may be completed at a time. However, there are two possible circuits (throws) that can be made.

TRANSLUCENT : Transmitting light so that objects lying beyond cannot be seen distinctly.

TRANSPARENT : Transmitting light so that objects lying beyond can be seen distinctly.

TWO CIRCUITS
: A circuit in which one circuit is completed in one position and another separate circuit is completed in an other position.

WIPING ACTION : Sliding of contacts over one another resulting in cleaning of the contacts.