Which of the following permits a microwave signal to travel in one direction with virtually no loss, but severely attenuates any signal attempting to travel in the reverse direction?

A. Waveguide match B. Cavity match C. Direct coax-helix match D. All of the above

A. A long time constant B. Low-pass filters C. The shortest possible time D. The restricted high-frequency response

A. $${\text{S}} = \frac{{2\lambda {\text{R}}}}{{\text{L}}}$$ B. $${\text{S}} = \frac{{3\lambda {\text{R}}}}{{\text{L}}}$$ C. $${\text{S}} = \frac{{\lambda {\text{R}}}}{{\text{L}}}$$ D. $${\text{S}} = \frac{{\text{L}}}{{\lambda {\text{R}}}}$$

A. To focus the beam of primary electrons B. To shield the electron beam from unidirectional magnetic C. As a second anode and to prevent the build-up of secondary field D. All of these