Switches.

A switch, properly defined, is any device by means of which a current may be diverted into any circuit, or be cut off therefrom entirely. Switches may be divided according to the manner in which they are moved, and thus we would obtain side-throw switches, plunger switches and vertical throw, or knife blade, switches. A side switch in its simplest form is shown in Figs. 86 and 87, the first being a top view and the second a side elevation.

Switches of this kind are generally arranged to move in one direction only, as is indicated by arrow C, and to prevent movement in other direction the stop post d is provided. This construction is advantageous, as with it in the switch can be closed rapidly without danger of swinging it beyond the closed position. In this position it will be seen that the current will pass from a to b through the switch blades. If the blade is raised in the direction of arrow C the circuit will be opened. When the switch is closed it is necessary that the blade rest firmly upon the stud b, and to render this certain a spring washer is provided at e, Fig. 87, and s is set so that it must spring up slightly to pass b.

Another modification of the simple side-throw switch is shown in Figs. 88 and 89, these being top and side views, respectively. The difference between this and the

Diagrams of switches.

former design is that the swiveling point is transferred from the end to the center of the switch blade. With this construction it would be easy for the blade to be raised from b by a downward pressure of the hand of the operator, and to avoid any trouble from such an occurrence the spring f is provided. This spring serves to hold the

blade down, as f and b are electrically connected, therefore the current would pass from S to f and thus to b.

In Fig. 90 is shown a switch that can be used for two purposes, one to connect one terminal of a line with two wires, and the other to open or close the circuit at two points at the same time. If the center stud a is connected with one terminal of the line, and b b are connected with separate wires, then it can be readily seen that when the switch blade is moved to the closed position as shown in the figure, the current entering through the wire connected with a will divide and pass out through two wires connected with b and the other with b1. If one

Multiple switches.

end of the line wire is connected with b and the other with b1, then if the switch blade is moved in the direction of arrows C, there will be a break in the circuit between S

and b and another one between S and b1, hence the two points in the circuit will be opened at the same time.

Diagram Fig. 91 represents what is called a singlethrow, single-break switch.

Diagram Fig. 92 represents a single-throw, doublebreak switch, and it will be noticed that the difference between it and Fig. 91 is, that S is not pivoted at a, hence when it is in the open position S is entirely disconnected from the circuit. When S is lowered it connects a with b, and when it is raised from this position, two breaks are