A species of switch which is actuated by the pressure of a button. In
its normal position the button is pressed outwards by a spring, and the
circuit is open. When pressed inwards, it closes the circuit. When
released it springs backward and opens the circuit again.

They are principally used for ringing bells. If the latter are of the
automatic type, they ring as long as the button is pressed.

For door-bells and room-bells, the button often occupies the center of a
rosette of wood or bronze or other ornamental piece. Sometimes, as shown
in the cut, they are constructed for use on floors to be pressed by the
foot. The general principle of their construction is shown, although the
method of making the contact varies.