Question

vacuum tube where replaced by dash and dash​

Answer 1

What we have to do

I can't understand

Answer 2

Vacuum tube - Wikipedia In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, and more economical than thermionic tubes. Beginning in the mid-1960s, thermionic tubes were being replaced by the transistor.