6-43 Table 6-1.—Description of Front Panel Controls, Indicators, and Connectors—Continued ITEM FUNCTION DESCRIPTION 20b 2dB/DIV When activated, this will increase the resolution so that each major graticule division represents 2 dB. 20c LIN When activated, this selects a linear display between zero volts (bottom graticule line) and the reference level (top graticule line) scaled in volts/division (see REFERENCE LEVEL, No. 23a). 20d PULSE STRETCHER When selected, this increases the fall time of the pulse signals so that very narrow pulses in a line spectrum display can be observed. 21 VIDEO FILTER One of two (NARROW OR WIDE) filters can be activated to reduce video bandwidth and high-frequency components for display noise averaging. The narrow filter is approximately 1/300th of the selected resolution bandwidth with the wide filter being 1/30th the bandwidth. Activating either one will cancel the other. To disable, completely switch filter off. 22 DIGITAL STORAGE Five push buttons and ON control operate the digital storage functions. With none of the push buttons activated, the display will not be stored. 22a VIEW A, VIEW B When either or both of these push buttons are selected, the push button illuminates, and the contents of memory A and/or memory B are displayed. With Save A mode off, data in a memory is interlaced with data from B memory. 22b B-SAVE A When activated, the differential (arithmetic difference) of data in B memory and the saved data in memory A are displayed. SAVE A mode is activated and SAVE A button will be lit. 22c MAX HOLD When activated, the digital storage memory retains the maximum signal amplitude at each memory location. This permits visual monitoring of signal frequency and amplitude at each memory location over an indefinite period of time. This feature is used to measure drift, stability, and record peak amplitude. 22d PEAK/AVERAGE This control selects the amplitude at which the vertical display is either peak detected or averaged. Video signals above the level set by the control (shown by a horizontal line or cursor) are peak detected and stored while video signals below the cursor are digitally averaged and stored. 23 MIN RF ATTEN This control is used to set the minimum amount of RF attenuation. Changing RF LEVEL will not decrease RF attenuation below that set by the MIN RF ATTEN selector. 23a REFERENCE LEVEL This is a continuous control that requests the microcomputer to change the reference level one step for each detent. In the 10 dB/DIV vertical-display mode, the steps are 1 dB or 0.25 dB if the FINE mode (No. 26) is selected. 23b MIN RF ATTEN DB This selects the lowest value of attenuation allowed: Actual RF attenuation is set by the microcomputer according to the logarithm selected by the MIN NOISE/MIN DISTORTION (No. 27) button. If RF attenuation is increased by changing MIN RF ATTEN, the microcomputer automatically changes IF gain to maintain the current reference level. 24 UNCAL This indicator lights when the display amplitude is no longer calibrated (selecting a sweep rate that is not compatible with the frequency span/div and resolution bandwidth). 25 LOG and AMPL CAL These adjustments calibrate the dynamic range of the display. The LOG calibrates any logarithm gain dB/Div, and the AMPL calibrates the reference level of the top graticule line at the top of the display. 26 FINE When activated, the REFERENCE LEVEL (No. 23a) switches in 1 dB increments for 10 dB/Div display mode, 0.25 dB for 2 dB/Div, and volts 1 dB for LIN display mode.