I am currently working on a project to amplify a very small signal (about 10 millivolts) using a vacuum tube. I understand vacuum tubes were used as amplifiers and transistors back in the day, but I can't figure out how they were used to power anything with the tiny amount of current they can deliver through the anode/cathode.

I'm looking to power a small relay with the amplified pulse.

I'm obviously missing something.

Can someone explain to me just how these were wired to perform the same function as transistors?