. The Bell System technical journal . anodically finished to resist corrosion. Thespring contact surfaces are silver plated. Prior to the introduction of this unit the receivers in general use fortelephone purposes in this country and abroad employed simpleresonant diaphragms and as a result had response characteristics whichwere characterized by prominent resonance peaks. As a rule the peakdue to the first overtone, as well as that due to the fundamentalresonance, fell within the important frequency range. This resonancenot only introduced frequency distortion but increased the intensitywith
. The Bell System technical journal . anodically finished to resist corrosion. Thespring contact surfaces are silver plated. Prior to the introduction of this unit the receivers in general use fortelephone purposes in this country and abroad employed simpleresonant diaphragms and as a result had response characteristics whichwere characterized by prominent resonance peaks. As a rule the peakdue to the first overtone, as well as that due to the fundamentalresonance, fell within the important frequency range. This resonancenot only introduced frequency distortion but increased the intensitywith which circuit disturbances such as clicks were , the diaphragms of these receivers were rigidly clampedbetween surfaces which differed in temperature coefficients of expansion 352 BELL SYSTEM TECHNICAL JOURNAL and heat capacities from those of the diaphragm with the result thatthe performance of the receiver was erratic and at a given time wasdependent upon the temperature changes to which it had 0. IIJ if) m R2 Ri L| i^VVS To mo So r3 m3 Ksmj L2 Sl T) mi S2 S3 -,— ^A^ EQUIVALENT CIRCUIT 1/ I ( CLOSED-COUPLER RESPONSECLOSED-COUPLER VOLUME = 6 CC) // \\\ X CALCULATED FROM EQUIVALENT CIRCUIT /// \ \\ EARLY TYPE RECEIVER, MEASURED X H^ ■^^ / \\ i-—> < ^ \ -^ ^y \ 7 \ \ i\ / \ X^ .y \ 11 ! /11 V /1/ ^x 1000 1500 2000 2500 FREQUENCY IN CYCLES PER SECOND Fig. 8—-Closed coupler response characteristics of the receiver. The new receiver is so designed that: 1. All prominent resonances within the important frequency range have been eliminated and the response within this rangematerially improved. 2. The effect of changes in temperature has been eliminated. INSTRUMENTS FOR THE NEW TELEPHONE SETS 353 3. These improvements have been accomplished without sacrificingsimpUcity of design or introducing features which compHcatemanufacture of the receiver or increase the maintenancerequired. Response.—An equivalent electrical circuit for the
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
