for a Meter having the Scale at the bottom. ....................... FIG. 73.—Details of the Wooden Parts which form the Case. ......... FIG. 74.—Showing how the Apparatus is arranged and connected for calibrating the Ammeter. .......................................... FIG. 75.—Showing how the Apparatus is arranged and connected for calibrating the Voltmeter. ........................................ FIG. 76.—A Pole changing Switch for reversing Small Motors or the direction of an Electric Current. ................................. FIG. 77.—Top view of a small Battery Rheostat ..................... FIG. 78.—Details of the Rheostat Base. The lower part of the illustration is a cross section. .................................. FIG. 79.—Looking at the Base from the bottom showing the grooves in which the Wires are laid. ......................................... FIG. 80.—The German-silver Resistance Wire is wound around a Fibre Strip. ............................................................ FIG. 81.—The Lever, Knob, Binding Posts, etc. ..................... FIG. 82.—The completed Rheostat. .................................. FIG. 83.—Key Frame. ............................................... FIG. 84.—Sounder Frame. ........................................... FIG. 85.—The Electro Magnets. ..................................... FIG. 86—The Sounder Armature. ..................................... FIG. 87.—Sounder Frame with Lever in Position. .................... FIG. 88.—Top View of Completed Instrument ......................... FIG. 89.—Side View of Key. ........................................ FIG. 90.—Key and Circuit Closing Levers. .......................... FIG. 91.—American Morse Code. ..................................... FIG. 92.—Circuit for Two Instruments. ............................. FIG. 93.—The Wooden Back for the Telephone. ....................... FIG. 94.—The Complete Telephone. .................................. FIG. 95.—Details of the Receiver Hook. ............................ FIG. 96.—Showing how the Push Button is arranged. ................. FIG. 97.—Circuit showing how to connect two Telephone Stations to the Line. ......................................................... FIG. 98.—Bobbin for Medical Coil. ................................. FIG. 99.—Bobbin with Winding. ..................................... FIG. 100.—Construction of the Core. ............................... FIG. 101.—Vibrator Parts and Core Cap. ............................ FIG. 102.—Regulator Tube. ......................................... FIG. 103.—The Base with Location of Holes. ........................ FIG. 104.—Top View of Finished Coil. .............................. FIG. 105.—Side View of Completed Coil. ............................ FIG. 106.—Vibrator Parts.