Paper sheets having recessed pressure-sensitive glued edge with a removable strip
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Audio transducer device for chin protector or breathing mask - has two internal recess fitting grooves, for securing valve housing and microphone-loudspeaker
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Watertight dynamic microphone capsule - uses sealed housing for coil topped by three membrane diaphragm system
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Noise reducing microphone for noisy environment - incorporates capsule enclosed between pair of stiff membranes and operates as pressure gradient microphone
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Cylindrical hand-microphone - has linear volume control slider which may be pressed inwards to activate on-off contacts
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HEADPHONE
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Moving coil diaphragms for electrodynamic listening apparatus
