Switch, Automatic.
A switch opened and closed by the electric current. It is used for
lighting distant incandescent lamps. It includes one or two
electro-magnets operated by two push buttons. In the usual arrangement
one button is black and the other white, for extinguishing and lighting
respectively. When the white button is pushed it causes a current to
pass through one of the electro-magnets. This attracts its armature,
thereby making a contact and throwing the lamps into the lighting
circuit. Then they remain lighted until the black button is pressed.
This excites the other magnet, which attracts its armature, breaks the
contact and extinguishes the lights.
The object of the automatic switch is to enable distant lamps to be
lighted without the necessity of carrying the electric leads or wires to
the place whence the lighting is to be done. A very small wire will
carry enough current to operate the magnets, and open circuit batteries,
such as Leclanché batteries, may be used as the source of current for
the switch, but generally the lighting current is used for the purpose.
A single magnet may do the work. When the lighting button is pressed the
magnet is excited, attracts its armature and holds it attracted, until
by pressing the black button the current is turned off from it. In this
case the lighting current is used to excite the magnet.
Switch Board.
A board or tablet to which wires are led connecting with cross bars or
other switching devices, so as to enable connections among themselves or
with other circuits to be made.
Switch, Circuit Changing.
A switch whose arm in its swing breaks one contact and swinging over
makes another. It is employed to change the connections of circuits from
one dynamo to another.
Synonyms--Changing Switch--Changing Over Switch.
Switch, Double Break.
A form of switch in which double contact pieces are provided to give a
better contact. One form consists of a hinged bar whose end swings down
between two pairs of springs. Both pairs are connected to one terminal,
and the bar to the other terminal of a circuit.
Switch, Double Pole.
A heavy switch for central station work, that connects and disconnects
two leads simultaneously.
Switch, Feeder.
A heavy switch, often of double contact type, for connecting and
disconnecting feeders from bus bars in central stations.