1)The vacuum tube raises the strength of the electrical signal. 2)The vacuum tube is raising the strength of the electrical signal. 3)The vacuum tube raised the strength of the electrical signal. 4)The vacuum tube will raise the strength of the electrical signal. 5)The strength of the electrical signal is raised by the vacuum tube.
2)The vacuum tube is raising the strength of the electrical signal.
3)The vacuum tube raised the strength of the electrical signal.
4)The vacuum tube will raise the strength of the electrical signal.
5)The strength of the electrical signal is raised by the vacuum tube.