Van Soest – Dutch Accoustic detector This early listening device named “van Soest” after the engineer who created it was developed in 1929. [...]Read … Posted March 8, 2023 (updated July 5, 2023) by Patrick
Barbier, Bénard and Turenne – French Listening Device This early accoustic warning device was from WW1 and still in use at the start of World War … Posted March 3, 2023 (updated July 5, 2023) by Patrick
