Anritsu Sitemaster S 251 B : 625 MHz to 2.5 GHz frequency range, Hand held S21 (transmission gain or loss), SWR / RL (standing wave ratio/return loss), and Distance-To-Fault (DTF) measurement instrument that includes a built-in synthesized signal source and an optional power monitor. Uses a keypad to enter data and a liquid crystal display (LCD) to provide a graphical indication of S21, SWR, or RL over the selected frequency range. Has a built-in distance-to-fault (DTF) capability. Capable of up to two hours of continuous operation from a fully charged internal battery and can be operated from a 12.5 VDC source.