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Radio Record, Volume I, Issue 41, 27 April 1928, Page 12

Moving-Coil Loudspeakers. (THE moving-coil loudspeaker is admitted to be the best type at present in existence, aud is well suited to farge rooms where ample volume com-. dined with quality is required. ‘This type of speaker usually requires about one ampere of continuous current to tuergise the electromagnet, and this fact makes it somewhat expensive to ‘uu, especially where mains current is aot available, Its principle depends apon the interaction hetween the electromagnet and a small coil attached to vhe back of the cone diaphragm, this soil carrying the current of varying amplitude from the plate circuit of the last andio valve. Small sizes are made with permanent magnets, obviating the heavy current consnmption. New Push-Pull Transformers. Fifi first shipment of Ferranti pushpull transformers is aboard the $.s. Westmoreland, shortly to arrive in few Zealand.

B Accumulator Voltages. The idea of utilising the whole output of a BD accumulator and cutting down voltages with resistances in the various plate circuits has one disadvantage, in that a certain amount of current is dissipated in the resistances, thus causing a higher consumption than in the case of employing tappings. ‘Ihe idea is not. suited to a dry battery in any case. This method eppeared in an American radio journal. A New Vernicr Condenser. DUBILIERE are marketing a new type of variable vernier condenser that will shortly be on sale in New Zealand. ‘This, known as the ‘"Univane," is so designed that each turn of the control knob turns one vane from zero to full-in position, the next turn puts in another vane in tle same way until all the vanes are full-in. This allows of very fine tuning in an easier tay than when the whole of the yanes move together. To assist in logging, a raidial indicates how many vanes are in use. The maximum capacity is .0005 mfd.