. La revue technique du système Bell . n l'oscillateur à quartz. Le réglage final de la fréquence est réalisé avec un petit condensateur cylindrique, d'une capacité d'environ 5 mmf., connecté en parallèle avec les électrodes en cristal. La taille de ce condenseur est chosentelle qu'un réglage d'une division sur le cadran correspond à un intervalle de fréquence d'environ une partie sur cent millions. Il y a 100 divisions sur le cadran et un total de 10 tours peuvent être effectués 502 BELL SYSTEM TECHNICAL JOURNAL correspondant à un ajustement total possible d'environ une partie en 100000. Ce condenseur est illustré en C dans
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. The Bell System technical journal . n the crystal oscillator. The final adjustment of frequency is made with a small cylindricalcondenser, having a capacity of about 5 mmf., connected in parallelwith the crystal electrodes. The size of this condenser is chosensuch that an adjustment of one division on the dial corresponds to achange of frequency of about one part in a hundred million. Thereare 100 divisions on the dial and a total of 10 turns may be made 502 BELL SYSTEM TECHNICAL JOURNAL corresponding to a total possible adjustment of about one part in100, 000. This condenser is shown at C in the circuit drawing. The oscillator circuit, showing the tubes and transformers, theplate tuning elements, the filament and plate current meters, and thefrequency adjusting condenser is shown in Fig. 12. The adjustingcondenser is mounted between the meters and is controlled by thelarge knob and dial. One complete oscillator unit, consisting of a 100, 000-cycle crystalcontrolled oscillator with three independent 100, 000-cycle outputs, . Fig. 12—Standard frequency oscillator without shield. having a self-contained temperature and pressure controlled crystal, and having a temperature controlled, electrically shielded circuit, isshown in Fig. 13. The submultiple generator circuit that is used to obtain outputs at10, 000 cycles and 1, 000 cycles is shown in Fig. 14. It consists of aninherently unstable vacuum tube oscillator with the tube operatingon the curved part of its characteristic. The frequency of thisoscillator may be controlled readily by any frequency which is asmall multiple or submultiple of it. In this instance the oscillator iscontrolled by an input having the frequency of its tenth harmonic, the controlling high-frequency input being resistance coupled into the A HIGH PRECISION STANDARD OF FREQUENCY 503 plate circuit of the lower frequency oscillator. The frequency of thecontrolled oscillator remains indefinitely at an exact submultiple ofthe controlling frequency. Two
