Tektronix 11A32 User's Reference Manual page 24

Operating the 11A32 in 11400-series Mainframes
The 11401 and 11402 oscilloscopes use offset to position the trace on the screen.
In YT (signal vs. time) mode offset determines vertical position, but when a
plug-in unit provides the X component of an XY display, offset controls
horizontal position.
Offset is an input-signal-related-control, and its units are those of the input
signal—usually
volts.
Offset subtracts a precision voltage from the input signal. To access the offset-
function, touch the double-ended arrow at the left edge of the screen. Control of
offset is then assigned to the Lower Control knob.
In the 11401 and 11402, changing the vertical deflection factor magnifies or
compresses the displayed signal about screen center. Therefore, to examine a
portion of the input signal in greater detail, use Vert Offset (the Lower Control
knob) to position the area of interest to screen center. Next, use the Vert Size (the
Upper Control knob) to adjust the display to the size needed for detailed
examination.
Two four-pole (24 dB/octave) bandwidth limit (low-pass) filters are available for
each 11A32 channel. The purpose of these filters is to reduce the amplitude of
unwanted noise or interference occurring at frequencies above the frequency of
the signal of interest. The user has a choice of cut-off (-3 dB) frequencies, either
20 MHz or 100 MHz, independently for each channel. The trigger, auxiliary
trigger, and display signal bandwidths for a channel are always the same. The
auxiliary trigger is the signal sent to the right plug-in compartment.
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11A32 User Reference Supplement