INPUT AUDIO
A microphone, tape recorder, FM tuner or other equip-
ment not normally connected to
the
rear panel connec-
tion of the MPI 4 may be plugged into
the
INPUT AUDIO
jack on the front panel. Signals are displayed on the screen
for observation or testing. During this time,
the
POWER
LEVEL selector must be set to the PREAMP position. The
size
of
the
display is
adjusted by
the GAIN control and
TRIM controls.
Some
microphones may not generate enough signal to
drive the display to comfortable viewing
levels.
This
can be corrected by adding a microphone preamplifier
between the microphone and AUDIO INPUT jack.
Level set Panel
information
AUDIO TRIM LEFT
Adjusts
trace
height for a left channel preamplifier audio
signal.
AUDIO TRIM RIGHT
Adjusts trace width for stereo display
or
trace height
for sweep or
level display from a right channel preampli-
fier
audio
signal.
SIGNAL STRENGTH
Adjusts trace
height above the
bottom or base line of
the multipath display.
DEVIATION
Adjusts
trace width of the
multipath display.
MULTIPATH POLARITY
The MULITPATH
POLARITY switch controls
polarity
of
the
signal-strength signal.
The
minus
position is used with
most tuners.
TRACE SEPARATION
The TRACE SEPARATION control adjusts the distance
between the two traces in the DUAL TRACE mode of
operation.
SWEEP EXPANSION
The SWEEP EXPANSION control adjusts maximum width
of the trace display. SWEEP EXPANSION operates only
when one or both of the DUAL TRACE pushbuttons are
pressed.
TRIGGER SOURCE
The TRIGGER SOURCE switch selects the signal used
to trigger the display sweep. In the DUAL TRACE mode
the sweep may be triggered from the left or right channel,
or from the 60 hertz line frequency.
FOCUS
The FOCUS control adjusts sharpness of the trace.
LOW PASS FILTER
The LOW PASS FILTER switch inserts or removes a filter
that eliminates 19,000 and 38,000 Hz stereo reference
signals. These unwanted signals produce fuzzy and in-
distinct traces on the screen. The most useful position is
the IN position. Only in special test procedures is it neces-
sary to switch the filter OUT,
RETICLE ILLUMINATION
The RETICLE ILLUMINATION switch turns illumination
of the screen scales on or off.
LEVEL MODE
In the NORMAL position the two columns rise and fall
like VU meters. In the PEAK position the columns indicate
the "average" peak level for signals that change con-
tinuously in amplitude. The Reset position resets the
Peak circuitry and freezes the highest level achieved by
the audio.
FIG. 7 LEVEL SET PANEL
8