. The Bell System technical journal . scillator by means of a crystal—in this case Rochelle salt—and has the primary crystal oscillator circuit is shown in Fig. The crystal is effectively in a pathbetween the resonating coil in the output and the grid, since the electrode ^ The Piezoelectric Effect in the Composite Rochelle Salt 1919,38, 1315. 2 See Patent 2,212,845 filed April 10, 1918; issued Aug. 27, 1940. -A. M. Nicolson, QUARTZ CRYSTAL APPLICATIONS 181 3 is in the direction of the smallest piezoelectric effect in Rochelle saltand contributes lit
. The Bell System technical journal . scillator by means of a crystal—in this case Rochelle salt—and has the primary crystal oscillator circuit is shown in Fig. The crystal is effectively in a pathbetween the resonating coil in the output and the grid, since the electrode ^ The Piezoelectric Effect in the Composite Rochelle Salt 1919,38, 1315. 2 See Patent 2,212,845 filed April 10, 1918; issued Aug. 27, 1940. -A. M. Nicolson, QUARTZ CRYSTAL APPLICATIONS 181 3 is in the direction of the smallest piezoelectric effect in Rochelle saltand contributes little to the action. If terminal one to the tapped coil isat the top of the coil, the circuit although employing a three electrodecrystal connection, effectively reduces to B in which the crystal is in the feed-back, path from plate to grid. On the other hand, if the tap is effectivelyat the bottom of the coil, the crystal is between grid and ground and feedbackoccurs through a distributed capacity from plate to grid. Both of these. ii ntniiiiiiiiiinniiiiin - II n-iii--ii -III Ill iiritt ■J J z- •-~ fn^rimij IImrurnrir / [S,* i .•?^-, Fig. —Ocean contour curves circuits B and C are widely used in oscillators of Pierce. Prof. G. published a circuit similar to circuit B, having a two electrodequartz crystal connected between grid and plate.^ In 1921, Professor Cady at Wesleyan University first showed* that quartz 3 Piezoelectric Crystal Resonators and Crystal Oscillators Applied to the PrecisionCalibration of Wave Meters, G. VV. Pierce, Amer. Acad, of Arts and Sciences, , 81-106. * The Piezoelectric Resonator W. G. Cad}, Proc. I. R. E. 1922, 10 83. 182 BELL SYSTEM TECHNICAL JOURNAL crystals could be used to control oscillators and that much more stableoscillators could be obtained in this fashion. These were later applied tocontrolling the frequency of broadcasting stations and radio transmitters ingeneral and about 1925 Mr. W. A. Marrison appHed the
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