Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 230 MISCELLANEOUS TRANSDUCERS that it is possible to predetermine the response and to evaluate the effect of changes in the constants of the component parts. Comparing the re- sponse of Figs. and it will be seen that large gains have been effected in uniform response over the entire range and in sensitivity from 1500 to 3000 cycles. B. Crystal Telephone Receiver. — A crystal telephone receiver^ consists of a light diaphragm connected to a Rochelle salt crystal, Fig. T
Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 230 MISCELLANEOUS TRANSDUCERS that it is possible to predetermine the response and to evaluate the effect of changes in the constants of the component parts. Comparing the re- sponse of Figs. and it will be seen that large gains have been effected in uniform response over the entire range and in sensitivity from 1500 to 3000 cycles. B. Crystal Telephone Receiver. — A crystal telephone receiver^ consists of a light diaphragm connected to a Rochelle salt crystal, Fig. The crystal as a driving system was considered in Sec. The three corners of a ' bender ' crystal are fastened to the case. The fourth corner is GB't CRYSTAL L ELECTRICAL miCMifMi CIRCUIT ESISTANCe S -CASE CROSS-SECTIONAL VIEW 1000 FREQUENCY EQUIVALENT CIRCUIT '-N^ v.^<: N A / ..^ \; Fig. Cross-sectional view, electric circuit and equivalent circuit of the mechanical system of a crystal telephone receiver. In the electrical circuit: e the voltage of the generator. rE\ the resistance of the generator plus the external series resistance, rsc and Cec the resis- tance and electrical capacitance of the crystal. In the equivalent circuit: ma the mass of the diaphragm. Cmv, and r^/o the compliance and mechanical resistance of the suspension. m\, Cm\ and vmx the mass, compliance and mechanical resistance of the crystal. Jm the force generated in the crystal. The graph shows the pressure response frequency characteristic. B. Receiver feeding a closed cavity. A. Receiver feeding an artificial ear. (After Williams.) fastened to the diaphragm. The impedance of a crystal telephone is pri- marily a capacitive reactance. Because of this fact the low frequency re- sponse may be raised relative to the high frequency response by connecting a high resistance in series with the receivers. A high resistance must be used because the impedance of the crystal is very high, being 80,00
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