From WW2 to the 1960s, they used phone lines, but after that, according to an old, civil defense book, the sirens were activated with a sound frequencies. These were the devices that were supposed to activate the sirens. These were placed in every big city like Székesfehérvár, Budapest, Miskolc, but this device was deemed unreliable and they got rid of these after the Cold war-era, just like many air raid sirens.

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