عکس/قبل‌از اختراع‌رادارهای‌الکترونیکی!

Aircraft Detection Before Radar...
I bet none of you ever saw this stuff before.
How air attacks were detected before radar...
Old time
acoustic
hearing aids




ACOUSTIC "EARS"
BEFORE RADAR - ON A SWIVEL













ACOUSTIC "EARS"
BEFORE RADAR -
GERMAN




ACOUSTIC "EARS"
BEFORE RADAR - ON WHEELS







ACOUSTIC "EARS"
BEFORE RADAR - ENGLAND