. The Bell System technical journal . Fig. 4- -Experimental bridge stabilized oscillator without provisionfor temperature control. Figure 5 shows the resistance of the lamp Ri plotted against thepower dissipated in its filament. The large rise in resistance for smallamounts of power is due to the efifective thermal insulation providedby the vacuum surrounding the filament and to low heat loss by radia-tion. The lamp operates at temperatures below its glow point, assur-ing an extremely long life for the 23 4-56 789 POWER INTO LAMP IN MILLIWATTS Fig. 5—Characteristic of lamp used for
. The Bell System technical journal . Fig. 4- -Experimental bridge stabilized oscillator without provisionfor temperature control. Figure 5 shows the resistance of the lamp Ri plotted against thepower dissipated in its filament. The large rise in resistance for smallamounts of power is due to the efifective thermal insulation providedby the vacuum surrounding the filament and to low heat loss by radia-tion. The lamp operates at temperatures below its glow point, assur-ing an extremely long life for the 23 4-56 789 POWER INTO LAMP IN MILLIWATTS Fig. 5—Characteristic of lamp used for Ri. THE BRIDGE STABILIZED OSCILLATOR 585 The particular value assumed by Ri in the circuit of Fig. 3 is ap-proximately (R2Rz)/Ri = [(100)(150)]/114 = ohms, and hencefrom Fig. 5 it follows that the power supplied to the lamp is about The voltage across the lamp is computed to volt, and across the entire bridge, volt. The power suppliedto a load of 150 ohms through the pad composed of R-; and Rs is accord-ingly milliwatt, or db below 1 milliwatt, which is in agreementwith measurements shown in Figs. 8 and 9, described below. Thesequantities are given to illustrate the fact that currents and voltages in K^b -— » a , 1 NORMALt- OPERATINGPOINT i1 n 1 » -•—< c,^ 60 80 100 120 140 160 180 200 220 240 260 PLATE BATTERY POTENTIAL IN VOLTS Fig. 6—Oscillator frequency vs. plate battery potential. a—Ci and C2 tuned for maximum amplifier —Ci and
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