The 54XXA is a microprocessor controlled scalar measurement system. This system is used to make scalar (magnitude) transmission, reflection, and absolute power measurements. A typical model is shown in Figure 1-1 (facing page). All measurement functions are selectable by using the front panel keys and controls together with the display screen menus. Section III describes this mode of operation. All 54XXA front panel control functions (except POWER on/off) are programmable via the IEEE–488 interface bus (GPIB). This function can be ordered as an option on all models (refer to paragraph 1-6). Remote operation of the 54XXA using GPIB commands is described in the GPIB User’s Guide for the 54XXA Series Scalar Measurement Systems that is located behind the Supplements/Options tab at the rear of this manual. The measurement frequency range of the 54XXA is determined by: · The range of the internal signal source of the particular model. · The external SWR Autotester and/or detector used with the 54XXA.