Datasheet

www.grayhill.com
Pushbutton Engineering Information
Pushbutton switches are selected not only
by their ratings, but also by their contact
type. While nearly all rotary switches and
DIP switches have wiping contacts, pushbut-
ton switches may have either wiping or butt
contacts (see internal views below).
Wiping Contacts are self-cleaning and usually
provide a low resistance in circuits where
contact resistance is critical. However, the
wiping action creates mechanical wear and
conductive wear products.
the switch. The rapid rate of make and break
means that these switches are appropriate for
high current loads. They usually have a slight
wiping action and contact surfaces made of
precious metals to minimize their disadvan-
tages.
Butt Contacts have less wear than wiping
contacts and therefore, have a longer life.
They are also smaller. Butt contacts are not
self-cleaning, so their contact resistance can
vary from operation to operation.
Snap Action switches are basically butt con-
tact switches with a spring mechanism which
provides the make and break. The mecha-
nism controls both the operating point and
the rate of operation, but adds to the wear of
Actuator: The part of the switch to which an
external force is applied to operate the switch.
Alternate Action (Push-Push) Switch: A
switch in which the operable position is
maintained after the rst actuation, and then
disengaged with the second operation.
Break-Before-Make Switch (BBM): A
double throw switch in which the moving
contact breaks the connection with the rst
circuit before
making contact with the second; also called
non-shorting switch.
Double Throw Switch: A switch which has
a normally open as well as a normally closed
circuit per pole.
Joystick Action Switch: (From Joystick,
the control for an airplane). A lever switch
which operates with momentary action in 4
directions, and is disengaged in the upright
position.
Make-Before-Break Switch (MBB): A double
throw switch in which the contacts makes con-
nection with the second circuit before
breaking contact with the rst; also called
shorting switch.
Maintained Contact Switch: A switch in which
the actuator remains in a position until it is actu-
ated to another position where it also remains
until actuated. Example: Push-Pull Switch.
Momentary Contact Switch: A switch in
which the shorting bar returns from its operated
position to its normal or free position when the
actuating force is removed.
Operating Position or Point: The position of
the actuator when the desired electrical action
(make or break of contact) occurs.
N.C., Normally Closed: Switch in which the
circuit is closed without actuation (with actuator
in the "normal" position).
N.O., Normally Open: Switch in which the
circuit is open without actuation (with actuator in
the "normal" position).
Overtravel: The distance or angle between the
operating position and the extreme position to
which the actuator may be moved.
Pole: An electrically isolated circuit within a
switch; a common terminal and all the selected
terminals to which it connects.
Pretravel: The distance or angle through which
the actuator moves from its free position to its
electrical operating position.
Single Throw Switch: A switch which has
only one normally open or one normally closed
circuit per pole.
Throw: See Single Throw and Double Throw.
Switch Terminology
Internal Views of Pushbutton Switches
Wiping Contact
Snap Action
Butt Contact
FIXED CONTACTS
RETURN
SPRING
SHORTING
BAR
BUSHING
ACTUATOR
INTERNAL
BUTTON
FIXED CONTACTS
RETURN
SPRING
SHORTING
BAR
BUSHING
ACTUATOR
ACTUATOR
BUSHING
FIXED
CONTACTS
OVERSPRING
MOVABLE
CONTACT
Specifications are subject to change. Please refer to the current datasheet on www.grayhill.com for the most current published specifications for this product.