I think it was supposed to withstand the electromagnetic pulse of a nuclear explosion - Special toys for the military in preparation of WW3. "Soviet Cold War–e

I think it was supposed to withstand the electromagnetic pulse of a nuclear explosion - Special toys for the military in preparation of WW3. "Soviet Cold War–era military aircraft often had avionics based on vacuum tubes due to limited solid-state capabilities and a belief that the vacuum-tube gear would survive better." says http://en.wikipedia.org/wiki/Nuclear_electromagnetic_puls http://en.wikipedia.org/wiki/Nuclear_electromagnetic_puls