. The Bell System technical journal . Pig. 1 — Schematic diagram of electronic relay tester. ELECTRONIC RELAY TESTER 927. cient gain to provide adequate deflection voltage to the horizontal platesof the scope. The oscillator comprises a 6AU6 pentode tube and an associated tankcircuit. The tube is connected as an electron coupled oscillator with theenergy for the oscillations being supplied by the screen circuit. The plateoutput is a modulated current that passes through the screen and sup-pressor grids. Considerable isolation of the coupling circuit from theoscillator is obtained by this arran

. The Bell System technical journal . Pig. 1 — Schematic diagram of electronic relay tester. ELECTRONIC RELAY TESTER 927. cient gain to provide adequate deflection voltage to the horizontal platesof the scope. The oscillator comprises a 6AU6 pentode tube and an associated tankcircuit. The tube is connected as an electron coupled oscillator with theenergy for the oscillations being supplied by the screen circuit. The plateoutput is a modulated current that passes through the screen and sup-pressor grids. Considerable isolation of the coupling circuit from theoscillator is obtained by this arran Stock Photo

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. The Bell System technical journal . Pig. 1 — Schematic diagram of electronic relay tester. ELECTRONIC RELAY TESTER 927. cient gain to provide adequate deflection voltage to the horizontal platesof the scope. The oscillator comprises a 6AU6 pentode tube and an associated tankcircuit. The tube is connected as an electron coupled oscillator with theenergy for the oscillations being supplied by the screen circuit. The plateoutput is a modulated current that passes through the screen and sup-pressor grids. Considerable isolation of the coupling circuit from theoscillator is obtained by this arrangement. An antiresonance circuit similar to the tank circuit is used to couplethe plate of the oscillator tube to the rectifier. Since the electron coupledoscillator acts as a high impedance generator or constant current sourcethe voltage across the coupling impedance is proportional to the valueof the impedance. Hence as the oscillator frequency is shifted by a changeill the position of the armature a corresponding shift occurs in the acvoltage across the coupling impedance and rectifier tube (6AL5). Theoutput volt

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RM2CNCX3M–. The Bell System technical journal . Fig. 5—Nail contacts used by Professor Hughes in 1878 to demonstrate their micro-phonic properties. 168 BELL SYSTEM TECHNICAL JOURNAL. Pig 6—Carbon pencil type microphone, mounted on a sounding board, demonstrated by Hughes in 1878.

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RM2CRW5YY–. The Bell System technical journal . Vertical AntennaTotal N.R.F. = 1.000Back End N.R.F. = 1.000 3 330^^^^ ? 300^/ /^ l/ ^ ^ X60» 24oV^ ^n/ r) /l20 2io^^];;;--- .J^O Loop AntennaTotal N.R.F. = 0.707Back EndN.R.F. = 0.707. Wave-Antenna(One Wave-Length Long)Total N.R.F. = 0.435Back End N.R.F. = 0.058 Wave-Antenna(Two Wave-Lengths Long)Total N.R.F. = 0.361Back End N.R.F. = 0.048 Pig, 5—Comparison of polar diagrams of simple antennas. (The unit for the radiiis output current into the same resistance for a constant impressed field.) efficiently, it is desirable that they be tuned, introducing th

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