GB326602A - Improvements in electro-static sound reproducers or transmitters - Google Patents

Abstract

326,602. United Reproducers Patents Corporation. Oct. 24, 1928, [Convention date]. Condenser telephones; diaphragms. -An electrostatic sound reproducer or transmitter comprises a pair of perforated undulated plates 1, 2 having troughs 3, 4, crests 5, 6 and intermediate slope portions 7, 8 between which are interposed rubber, silk or rubberized silk dielectrics 10, 11 provided on their inner sides with one or more flexible metallic conductors 12, such as gold leaf, aluminium foil &c. The undulations in the plates 1, 2 may be of the cavity or concaved type or may extend from one side of a plate to the other, and the dielectrics and flexible conductors are preferably cemented together to form a single unit. The device may be used with a push-pull circuit (Fig. 2, not shown) or with the circuit shown in Fig. 3, in which the plates 1, 2 are connected to the ends of the split secondary 53 of the audio transformer 50, the centre point 56 being connected through a condenser 58 with the flexible conductor 12. Leads 64, 65 extend from each side of the condenser 58 to a battery or other source of E.M.F. for maintaining conductor 12 at a different potential from that of the plates 1, 2. Choke coils 60, 61 or resistances 62, 63 may be inserted in these leads to prevent the transmission of audible frequency currents and disturbances, such as A.C. hum.