At least two, one for each Cold War power: - ERCS: https://en.wikipedia.org/wiki/AN/DRC-8_Emergency_Rocket_Communications_System https://en.wikipedia.org/wiki/

At least two, one for each Cold War power: - ERCS: https://en.wikipedia.org/wiki/AN/DRC-8_Emergency_Rocket_Communications_System https://en.wikipedia.org/wiki/AN/DRC-8_Emergency_Rocket_Comm... - Perimeter: https://en.wikipedia.org/wiki/Dead_Hand https://en.wikipedia.org/wiki/Dead_Hand