Tektronix 070-8811-08 - Manual (Page 43)

Operating Basics
28 764 Digital Audio Monitor User Manual
+1 when the channels contain identical signals (frequency and
phase); it will measure –1 when the signals have the same frequency
(or frequencies), but are 180 degrees out of phase. A center-scale (0)
reading indicates uncorrelated — or random — signals.
Figure 22: The phase correlation meter
When you monitor audio programs (as opposed to simple test tones)
with the 764, the pointer will usually read between +0.5 and +1, and
will move as the correlation between the two channels changes.
Choose the time constant of the meter — and thus the speed of meter
response— through the Phase Display submenu.
AGC
AGC (automatic gain control) keeps the Lissajous pattern visible and
within the bounds of the phase display for signal levels between
0 dBFS and approximately –40 dBFS. When the AGC is Off, full
scale is equivalent to the Peak Program level (refer to page 20). AGC
does not affect the correlation meter Press the bottom soft button
(immediately above CLEAR MENU) to toggle AGC On/Off.