GB418330A - Improvements in or relating to sound recording lamps and circuits therefor - Google Patents

Abstract

418,330. Discharge lamps. TREVIRANUS, H. A., Mombasa, Kenya Colony, East Africa. Dec. 21, 1933, Nos. 36041 and 36042. Convention dates, Feb. 13, and Sept. 9. (Class 39 (i).] In a lamp used in sound recording, a point-like glow discharge is obtained by arranging the cathode c of almost circular or semi-circular form about the end of the anode a, which is encased in a quartz or glass tube b ; a screen d, charged positively, surrounds the electrodes and has a hole d<1> for the emission of the variable light. The whole is enclosed in a bulb with mercury or other metal vapour filling. The cathode consists of a wolfram wire 1, Fig. 4, surrounded by a spiral 4 of nickel band on edge which spiral is coated with barium or barium oxide. The wolfram wire is heated by a battery 6, Fig. 6, with adjustable resistance 21 ; this battery is also connected through the adjustable resistance 15 to the screen 14 to charge it positively. A steady glow is obtained by a battery 12 connected through a variable resistance 13 to the mid-point 7 of the cathode and to the anode 2. The speech current is transmitted through the transformer 9 whose secondary is connected to the anode and through a condenser 11 to the cathode. The battery 12 may be in series with the transformer secondary. In modified circuit arrangements wherein it is not necessary to connect the lead from the transformer to the mid-point 7 of the cathode. The connection is made to the ends the transformer being connected to the anode and to a point between two condensers 17<a>, 17b, Fig. 9, and an inductive resistance being connected to the ends of the cathode ; the inductive resistance may be omitted. In one form the cathode is heated by alternating- current, the screen being charged from the anode battery.