Oldfags remember.
https://www.warhistoryonline.com/war-articles/he-managed-to-convey-the-truth-by-blinking-torture-in-morse-code-during-the-vietnamwar.html
Oldfags remember.
https://www.warhistoryonline.com/war-articles/he-managed-to-convey-the-truth-by-blinking-torture-in-morse-code-during-the-vietnamwar.html