Comment by himinlomax

I heard a story according to which a similar scheme was used in the Algerian war of independence, so these is more retro than scifi. Radio sets were left by the French military for the Algerians to grab. The explosive was hidden in the frame and components, and the trigger was a specific audio frequency. The device looked exactly like a stock military radio set if you disassembled it. So it's not that scifi.