Coil about 240 turns No. 28 S.W.G. aluminium wire to suit gap but with tripod broken away
Coil about 240 turns No. 28 S.W.G. aluminium wire to suit gap but with tripod broken away, part of Oliver Lodge’s microphone amplifier or relay, 1898 (British patent 9712 of 1898) ), a precursor of the moving-coil loudspeaker
