Capacity, effect upon frequency, 100; measurement of, 104; unit of, 104; variable, 107 Capacity effects, 243; elimination of, 228 Carrier current, modulation of, 146; telephony, 255 Characteristic, of vacuum tube, 68, 74; effect of B-battery upon, 128; how to plot a, 70 Characteristic curve of transformer, 64 Chemistry, 8 Choke coils, 210, 221 Circuit, A, B, C, 187; coupled, 115; defined, 43; oscillating, 113; plate, 45; short, 30; tune of a, 117 Condenser, defined, 77; charging current of, 78; discharge current of, 80; impedance of, 135; theory of, 78; tuning, 224 Common battery system, 254 Connection for wire to radio, 254 Continuous waves, 86 Copper, atomic number of, 13 Copper sulphate, in solution, 21 Crystals, atomic structure, 147 Crystal detectors, 146; characteristic of, 148; circuit of, 150; theory of, 147 Current, transient, 114; radio, 144 Cycle, 94, 97 Damped oscillations, 114 Demodulation, 231 Detection, explained, 146 Detectors, audion, 126; crystal, 146 Direct currents, 205 Dissociation, 22 Distortion, of wave form, 163 Dry battery, 27 Earth, atomic constitution, 11 Effective value, of ampere, 207; of volt, 207 Efficiency, of regenerative circuit, 182 Electrical charge, 22 Electricity, current of, 15, 16 Electrodes, of vacuum tube, 41; definition of, 41 Electrolyte, definition of, 34 Electrons, properties of, 4; planetary, 10, 12; rate of flow, 48; vapor of, 39; wandering of, 14 Electron streams, laws of attraction, 200 E. M. F., 59; alternating, 76; of self-induction, 238 Energy, expended in tube, 235; of electrons, 113; radiation of, 125 Ether, 88 Feed-back circuit, 182 Frequency, 98, 158; effect upon pitch, 133; interval, 247; natural, 117; of voice, 163 Fundamental note, of string, 157 Gravity battery, theory of, 23 Grid, action of, 47; condenser, 169; current, 173; leak, 171; leak, construction, 172, 216; of audion, 41 Harmonics, 160 Helium, properties of, 9 Henry, 83 Heterodyne, 181 Hot-wire ammeter, 51 Human voice, mechanism of, 152 Hydrogen, action of in acid, 7; atom of, 7 Impedance, of coil, 136; of condenser, 136; of transformer, 195; effect of iron core upon, 207; matching of, 196 Intermediate-frequency amplification, 242 Inductance, defined, 83; effect upon frequency, 100; impedance of, 135; mutual, 109; of coils, 101; self, 83; table of values, 227; unit of, 83; variable, 108 Induction, principle of, 208