3-19 POLES THROWS BREAKS NUMBER OF POSITIONS MOMENTARY POSITIONS LOCKED POSITIONS ACTUATOR RATING A 2 1 1 2 — — PUSH BUTTON 115Vdc 5A B 2 2 2 3 1 OUT-3 TOGGLE 150Vdc 5A C 2 2 1 3 1 OUT-3 ROCKER 115Vdc 10A D 1 2 1 3 1 OUT-3 TOGGLE 115Vdc 5A E 2 2 1 3 — OUT-3 ROCKER 150Vdc 10A F 2 2 1 3 1 OUT-3 TOGGLE 150Vdc 10A G 2 2 1 3 1 IN-3 TOGGLE 115Vdc 10A H 2 2 1 3 1 OUT-3 ROCKER 115Vdc 3A I 2 2 1 3 1 OUT-3 ROCKER 28Vdc 5A Table 3-1.—Replacement Switches and Their Characteristics SOLENOIDS A SOLENOID is a control device that uses electromagnetism to convert electrical energy into mechanical motion. The movement of the solenoid may be used to close a set of electrical contacts, cause the movement of a mechanical device, or both at the same time. Figure 3-17 is a cutaway view of a solenoid showing the solenoid action. A solenoid is an electromagnet formed by a conductor wound in a series of loops in the shape of a spiral. Inserted within this coil is a soft-iron core and a movable plunger. The soft-iron core is pinned or held in an immovable position. The movable plunger (also soft iron) is held away from the core by a spring when the solenoid is deenergized. When current flows through the conductor, it produces a magnetic field. The magnetic flux produced by the coil results in establishing north and south poles in both the core and the plunger. The plunger is attracted along the lines of force to a position at the center of the coil. As shown in figure 3-17, the deenergized position of the plunger is partially out of the coil due to the action of the spring. When voltage is applied, the current through the coil produces a magnetic field. This magnetic field draws the plunger within the coil, resulting in mechanical motion. When the coil is deenergized, the plunger returns to its normal position because of spring action. The effective strength of the magnetic field on the plunger varies according to the distance between the plunger and the core. For short distances, the strength of the field is strong; and as distances increase, the strength of the field drops off quite rapidly.