Fig. 143 is a diagram of a vibrator coil. CC represents the core composed of soft iron wires. PP is the primary winding and SS the secondary. There is no connection between these windings and they are carefully insulated. Y is the vibrator or _trembler_ and D the center about which it vibrates. W is a switch used for opening and closing the primary circuit; B, a battery of five cells. The point of adjusting screw A rests against a platinum point R soldered upon the vibrator. [Illustration: FIG. 143.--Diagram of a vibrator coil. The parts are as follows: A, contact screw; B battery; C, core; D, vibrator terminal; G, condenser; P, primary winding; S, secondary winding; W, switch; Y, vibrator. When the switch is closed, the following cycle of actions take place: 1, the primary current flows and magnetizes core; 2, magnetized core attracts the vibrator and breaks primary circuit; 3, the magnetism vanishes, including a momentary high tension current in the secondary winding; 4, magnetic attraction of the core having ceased, vibrator spring renews contact; 5, primary circuit is again completed and the cycle begins anew.] If the switch W be closed, the electric current generated by the battery B will flow through the primary winding. This will cause the core CC to become magnetized, and the vibrator Y will at once be drawn toward it. This will break the connection at R. The core, being made of soft iron, immediately upon the interruption of the current, will again lose its magnetism, and the vibrator will return to its original position. This again closes the circuit, after which the operation of opening and closing it is repeated with great rapidity so long as the switch W remains closed. [Illustration: FIG. 144.--Circuit diagram of a master vibrator coil. B, is the battery; C, the unit coils; C1, C2, etc., the condensers; P, the primary windings and S, the secondary windings; H1, H2, etc., the spark plugs; T, the timer; MP, the master primary; V, the vibrator; W, the common primary connection; 1, 2, etc., the stationary contacts of the timer.] The cycle of actions may be briefly stated as follows: 1. A primary current flows and magnetizes the core; 2. The magnetized core attracts the vibrator which breaks the primary circuit; 3. The core loses its magnetism and the vibrator springs back to its original position; 4. The vibrator, by returning to its original position, closes the primary circuit and the cycle begins again. [Illustration: FIG. 145.--The Splitdorf master vibrator coil. As shown in the illustration the several unit coils are indicated by the figures 1, 2, 3, and 4. A fifth unit V at the left contains the master vibrator. The primary wires P connect with the timer and the secondary wires S with the plugs. B B shows the battery connections.]