GB245810A - Improvements in telephone transmitters and receivers and the like - Google Patents

Abstract

245,810. Western Electric Co., Ltd., (Western Electric Co., Inc.). Aug. 14, 1924. Piezo-electric instruments.-Relates to improvements in piezoelectric telephone receivers and transmitters. (1) An electrode 60, Fig. 6 is embedded in the crystal, either by allowing the crystal to grow about one or more conductors or by inserting it in a hole drilled in the crystal. This electrode may take the form of a column of mercury, saturated Rochelle salt solution or graphite, or a wire surrounded by tinfoil pellets, graphite or conducting liquid insuring low contact resistance with the crystal. Two such conductors may be joined to a binding post anchored to the crystal bv cement. A torsion arm 66 connects one end of the crystal to a diaphragm. (2) the crystal 70, Fig. 9 is secured in a frame 71 by means of an internal electrode 74. The other electrode is a girdle 73. A tube 76 containing water or salt solution and having its upper end sealed may supply moisture to the interior of the crystal. A conical diaphragm has its apex attached to a torsion arm fixed to one end of the crystal. (3) A piezo-electric crystal is associated with a large diaphragm unrestrained in its periphery (4) The motional impedance of a diaphragm is made approximately equal to that of the crystal by annular corrugations in a conical diaphragm, which corrugations are closer together at the apex than at the periphery. Or the diaphragm, Fig. 4 may be composed of graded masses 50, 51, 52, which decrease, in density towards the periphery, and the periphery may be corrugated. A metal ferrule 53 in the form of concentric cores may be used in connecting the diaphragm. A stiffener 54, Fig. 5, of moulded sodium potassium tartrate may be used to reduce the transition loss between the ferrule and the diaphragm. Specifications 231,216 and 231,409 are referred to.