The aim of the topophone, which was invented and patented by Professor A. M. Mayer, is to enable the user to determine quickly and surely the exact direction and position of any source of sound. Our figure shows a portable style of the instrument; for use on ship-board it would probably form one of the fixtures of the pilot-house or the “bridge,” or both. In most cases arising in sailing through fogs, it would be enough for the captain or pilot to be sure of the exact direction of a fog horn, whistling buoy, or steam whistle; and for this a single aural observation suffices.

Sound collectors for detecting aircraft before RADAR

Sound collectors for detecting aircraft before RADAR

Sound collectors for detecting aircraft before RADAR

Sound reflector for detecting aircraft before RADAR