A Czech acoustic aircraft locator made by Goerz used in Finland during World War 2. Before radar, this technology was used between WW1 and WW2 by air defense forces to locate incoming enemy aircraft by the sound of their engines. This unit was used to direct searchlights to illuminate the aircraft to target antiaircraft fire. The unit consists of two pairs of "scoop" sound collectors, one pair in the horizontal axis to determine the aircraft's azimuth, and one offset pair in the vertical axis to determine the aircraft's elevation. Sound ducts from each pair conducted the sound to the ears of a technician.