LIGHT MICROPHONE SET.
GEOPHONE SOUND RANGING SET.
AMERICAN T-M SURFACE SOUND-RANGING SET.
CHAPTER IV.
SOUND AND FLASH RANGING AND SEARCHLIGHTS.
In childhood we were enthralled by the tales of those magic persons whose keen hearing could detect even the whisper of the growing grass. As camouflage developed, modern warfare yearned for such supernatural gifts of sense that troops might detect the unseen presence of the enemy. Accordingly Science, the fairy godmother of today's soldiers, raised her wand, and lo, the Army was equipped with the wonderful ears of the fairy tale, uncanny no longer, but a concrete manufacturing proposition.