Van Soest – Dutch Accoustic detectorThis early listening device named “van Soest” after the engineer who created it was developed in 1929. [...]Read … Posted March 8, 2023 (updated February 28, 2025) by Patrick
Barbier, Bénard and Turenne – French Listening DeviceThis early acoustic warning device was from WW1 and still in use at the start of World War … Posted March 3, 2023 (updated February 28, 2025) by Patrick
