Tektronix 2714 User Manual page 251

The Display Line and Limit Detector
100.0MHz (AUTO SWEEP) ATTN 2DB
18.8DBMV VF WIDE
50.0MHz/ 10 DB/
5MHz RBW (AUTO) CALIBRATOR
The 2714 provides a convenient method to determine whether a signal
peak is higher or lower than some particular level, or whether it falls
within a specified range. The DISPLAY LINE feature displays a hori-
zontal line at the level you specify. You can visually compare signal
amplitudes to the line or set the 2714 to sound an alarm if a signal
crosses the line.
To see the DISPLAY LINE feature in action, press [DSPL] [8], and
select item 2, VALUE ENTRY. Enter -2.2 dBmvV by pressing [2] [e} [0]
[W}.
The 2714 reverts automatically to the spectral display that now con-
tains a horizontal line two divisions down (— 2.2 dBmV). You will notice
the A register red LED is lit. When you display the line, you cannot
display the contents of the A register. Data stored in A are not de-
stroyed, but you cannot see them until you turn off the line.
There is another way to set the level of the line. Turn on the marker and
set it at the peak of the calibration signal third harmonic. Press [DSPL]
[8] again and select item 3, DISPLAY LINE TO MARKER. The spectral
display reappears with a horizontal tine at the marker position. This
provides a convenient way to identify all signals greater or less than
another signal. If the marker is not turned on when item 3 is selected,
you receive an error message.
Press [DSPL] [8] again and select item 4, LIMIT DETECTOR. The
end-of-line status indicator changes to OVER; the display line has
been made an upper limit. If an on-screen signal goes over the limit,
Press [DSPL] to return to the spectral display. The alarm should be
sounding. When the limit detector and the display line are both se-
lected, the marker automatically turns on and moves to the highest
signal peak on screen. This feature enables you to quickly read the
amplitude of the largest signa! after the alarm alerts you that the limit
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