The medical coil is very easy to connect. Run the inside primary terminal to the binding post on the rear left hand corner of the base. Connect the other terminal to the vibrator post. A wire should be led from the adjustment screw post to the binding post mounted on the forward left hand corner of the base. [Illustration: FIG. 106.—Vibrator Parts.] One or two cells of battery should be sufficient to operate the coil. Connect the battery to the two binding posts. Adjust the thumbscrew until the contact on the end just touches the contact point on the vibrator spring. The current will then flow through the primary winding and magnetize the core. The magnetism of the core will draw the armature towards it, thus pulling the contacts apart and interrupting the current. The process will repeat itself very rapidly at a speed depending upon the adjustment of the thumbscrew and as long as the battery remains connected. [Illustration: FIGS. 107 and 108.—Two Types of Handles.] The handles for the coil are very easily made out of a piece of brass tubing about two and one-half inches long and five-eighths of an inch in diameter. They can also be made by rolling a piece of sheet brass or tin into a tube and soldering the edges together. The illustration shows two methods of making the handles and attaching the cords. The handle in the upper part of the illustration is made from a piece of tubing. A wooden plug or cork is fitted into one end. The wire passes through a hole in the centre of the plug and is turned back over the edge so that when the plug is forced into the tube, the wire will make contact with it. The handle in the lower part of the illustration is made from one of the brass cylinders in which the indelible ink for rubber stamps is supplied. A hole is bored in the bottom through which the wire passes. The end of the wire is soldered to a piece of stiff brass wire bent into the shape of a hairpin. The ends of the wire are spread apart so that they will spring against the inside of the tube. The connector is then pulled up inside of the handle. The flexible wires or "cords" as they are sometimes called, attached to the handles, should be about eighteen inches long. The opposite ends to the handles should be led through two holes in the base, in front of the bobbin. The left hand cord should be connected to the vibrator post and the right hand cord to the outside secondary terminal.