Action

The action of a switch describes how it operates.

Momentary action

Momentary switches only make contact momentarily (between actuation and release)

Alternate action

These switches alternate between open and closed every time they are pressed, hence the name

Latching action

Same as alternate action — typically, alternate action switches have a mechanical latch that holds the mechanism closed, and frequently (but not universally) the slider remains partially depressed when the switch is closed, giving visual state indication

Normally open (NO)

The switch is open (disconnected) when released, and closed (connected) when depressed

Normally closed (NC)

The switch is closed when released, and open when depressed