The S331B option 5 includes the power meter. The base model (S331B SiteMaster) is a hand-held SWR/RL (standing wave ratio/return loss) and Distance-to-Fault measurement instrument that includes a built-in synthesized sweep signal source. The S331B uses a keypad to enter data and an LCD to provide a graphical indication of SWR or RL over the frequency range. The S331B is designed primarily for providing an all-in-one measurement solution for SWR, return loss or cable insertion loss,and location of faulty RF components in antenna tower systems. N(f) connection.