在60年代的越南战争期间,北越方面利用在热带丛林中修筑的“胡志明小道”。调动部队,运送物资。美军则依仗其空中和技术优势,极尽其能,以图切断“胡志明小道”。“热带树”即是美军当时秘密使用的一种新型无人值守传感器。它实际上是一种地面震动/声传感器,由飞机沿“胡志明小道”投 During the Vietnamese war in the 1960s, North Vietnam used the “Ho Chi Minh trail” built in the tropical jungle. Mobilize troops and deliver supplies. The U.S. military, relying on its advantages in air and technology, did its utmost to cut off the “Ho Chi Minh Trail.” The “tropical tree” is a new type of unattended sensor that the US military secretly used at that time. It is actually a ground-based vibration / sound sensor, cast by aircraft along the Ho Chi Minh Trail