Moving Coil Speaker

Radio Record, Volume III, Issue 27, 17 January 1930, Page 32

Moving Coil Speaker

EXPERIMENTERS who use movingcoil loudspeakers in which the ‘field is energised from an‘ accumulator often . find, to: their annoyance, that ‘although they. switched off the set on the. previous occasion they had not switched . off the energising current, with the result that, the accumulator has run down. ,Troubles of this kind ean be largely avoided .by .using .a filament. jack mounted on the baffle board or cabinet. and so wired that the insertion. of this plug, connected to the output terminals of the set, will both connect the .speaker and simultaneously. switch on, the field current. The use of the plug in this way is rather.a reversal of the usual prac- . tice; for: generally the speaker is connected, to the "free ends" of: the lead and the jack inserted jin the set. Such a device: shows clearly whether the speaker is connected or not,.:and saves running down the accumulator needlessly. Of ‘course, in a case where a plug has to be inserted in a jack in the set, the loudspeaker leads will have two plugs. A glance | shows whether the plug is in the speaker or not, while the position of a switch is not easily seen from a distance. ? wh?