Page 5 Advertisements Column 3

Otago Daily Times, Issue 20039, 4 March 1927, Page 5

the valve. For a Riven filament the number of electrons thus discharged depends upon the heat generated in the filament; that is, upon the temperature of the latter. Filaments can he made of different materials, and it is found that certain substances do not need to bo heated to so high a temperature as others in order to obtain the same electron discharge. And since a low temperature means a low current consumption, the most economical type of filament is one which gives a high electron discharge at a low temperature. A bright valve consumes, on an average, about 7 of a unit of current under normal working conditions, whilst no dull-emitter on the market (other than special power amplifiers) consumes more than .3a of a unit. Many other dullemitters work on .15 of a unit, or thereabouts; and there i. a special type of dull-emitter which is callable of bringing in good signals of a filament consumption of .06 of a unit. Those very low-tempera-ture valves are designed to operate entirely on dry cells. The dull-emitter type of valve is certainly the valve of the future —and the duller the better. The SFERAVOX reproduces with remarkable clarity, is free from distortion, and so constructed that no matter if the terminals arc connected the wrong way, the magnets cannot become de-magentised. £5 ss. off all leading radio dealers.—N.Z. Reps., Brown and Bureau (Ltd.), Wellington.—Advt. I