Other forms of Korean psychological battle have included loudspeaker blaring, setting up giant front-line electronic billboards and signboards and propaganda radio broadcasts.

She began to put her texts on electronic signboards in the early 1980s.

At crucial intersections, signboards were posted, pointing the way.

“Hydrogen,” he said slowly in English, gesturing at an imaginary signboard.

It said other details of the visiting rules are posted on signboards in front of the prisons.