. The Bell System technical journal . DIM. CMS. P E N S ^CAPILLARY TUBESFOR HYDROGEN Fig. 5—Schematic of condenser transmitter and thermophone. resistance. Sound vibrations impinging on the diaphragm actuate itand produce variations in the capacity of this instrument. The 546 BELL SYSTEM TECHNICAL JOURNAL resulting alternating potentials, faithfully representing the soundpressure waves, are amplified by the associated amplifier. Betweenthe first and second stages of this amplifier, provision has been madefor the introduction of distortion networks to simulate the distor
. The Bell System technical journal . DIM. CMS. P E N S ^CAPILLARY TUBESFOR HYDROGEN Fig. 5—Schematic of condenser transmitter and thermophone. resistance. Sound vibrations impinging on the diaphragm actuate itand produce variations in the capacity of this instrument. The 546 BELL SYSTEM TECHNICAL JOURNAL resulting alternating potentials, faithfully representing the soundpressure waves, are amplified by the associated amplifier. Betweenthe first and second stages of this amplifier, provision has been madefor the introduction of distortion networks to simulate the distortionof any transmitting system. Between the last two stages are attenu-ating networks permitting adjustment of the relation between trans-mitter input and transmitter output over a range of 22 db in steps of. Fig. 6—-Thermophone in chamber for calibrating transmitter. db. The output impedance of the amplifier is 600 ohms withnegligible phase angle. The reference line consists of a series of balanced resistance net-works. This line has a characteristic impedance of 600 ohms matchingthe output impedance of the reference transmitter and the inputimpedance of the reference receiver, thereby eliminating any reflectionefiects at these junctions. By means of suitable controls the attenu-ation may be varied over a range of 101 db in steps of db. The reference receiver consists of a moving coil receiver and associ-ated three-stage amplifier. Means are provided for adjusting therelation between the input to the receiver and its output over a range REFERENCE SYSTEM FOR TELEPHONE TRANSMISSION 547 of 22 db in steps of db. As in the case of the reference transmitter,provision has been made for the introduction of distortion networksto simulate the distortion of any receiving system. In the
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
