Pushbutton Switches
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Pushbutton switches are mechanical switches defined by the method used to activate the switch. The activation method is typically in the form of a plunger that is pushed down to open or close the switch.  Pole and throw configurations for pushbutton switches can be single pole single throw (SPST), single pole double throw (SPDT), double pole single throw (DPST), double pole double throw (DPDT), or solid-state.  SPST is a switch that makes or breaks the connection of a single conductor in a single branch circuit. This switch typically has two terminals. It is commonly referred to as a "Single-Pole" Switch.  SPDT is a switch that makes or breaks the connection of a single conductor with either of two other single conductors. This switch typically has 3 terminals, and is commonly used in pairs and called a "Three-Way" switch.  DPST is a switch that makes or breaks the connection of two circuit conductors in a single branch circuit. This switch typically has four terminals.  DPDT is a switch that makes or breaks the connection of two conductors to two separate circuits. This switch typically has six terminals and is available in both momentary and maintained contact versions.  A solid state switching mechanism includes transistors and piezoelectric materials.  A normally open (NO) switch has contacts that are open or disconnected in their unactuated (normal) position.  A normally closed (NC) switch has contacts that are closed or connected in their unactuated (normal) position.

The actuator in pushbutton switches can be recessed, flush, or raised.  A recessed pushbutton actuator is within base, this is useful to protect against accidental actuation.  A flush pushbutton is flush with the base; typical example would be a doorbell.  A raised pushbutton resembles a plunger; typical example would be a pedestrian cross walk button. The switch function can be maintained contact, alternating contact, or momentary contact.  In a maintained contact switch an actuator stays in thrown position. This includes on-off, but it also includes Three-Position - (Center-off) and Three Position - (No Center-off) switches where the switch remains in its actuated position.  Alternating action such as push on, push off characterizes an alternating contact.  In a momentary contact switch the switch must be held in position; it reverts to normal position when actuating force is removed.

Important switch specifications to consider when searching for pushbutton switches include maximum current, maximum AC voltage, maximum DC voltage, and maximum power.  Choices for terminal types for pushbutton switches include feed-through style, quick connect or blade, right angle PC pins, screw terminals, side PC pins, solder terminals, straight PC pins, surface mount technology, and wire leads.  Construction materials for the base or housing and the pushbutton include thermoplastics or metals.  Features common to pushbutton switches include CE certification, CSA certification, UL listing, dustproof, high inrush current compatible, illuminated switch, imprinted markings, locking switch, pilot light, tape and reel packaging, time delay, vandal proof, wiping contacts, and weather resistant or waterproof.
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