PS Engineering
PMA450B Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-450-0600
Page 3-5
Rev. 5, August 2020
To exit PA mode, push and hold the N1 button again until
PA
is off or cycle power on the audio panel.
Marker Beacon Operation (9) (part number 050-450-0601, -0701 only)
The Marker Beacon Receiver uses visual and audio indicators to alert you when the aircraft passes over a 75
MHz transmitter.
The audio from the Marker Beacon Receiver can be heard by pushing the "
MKR
" button. AUD will light up
green.
The Blue lamp, labeled “O”, is the Outer Marker lamp and has
an associated 400-Hertz 'dash' tone. The lamp and tone will be
keyed at a rate of two tones/flashes per second when the aircraft
is in the range of the Outer Marker Beacon.
The Amber lamp, labeled “M”, is the Middle Marker lamp and
is coupled with a 1300 Hertz tone. It is keyed alternately with short 'dot' and long 'dash' bursts at 95 combi-
nations per minute.
The White lamp, labeled “I”, is the Inner marker and has a 3000 Hertz 'dot' tone. The lamp and tone will be
keyed at a rate of six times per second.
Holding the
MKR
button for one second activates marker test lamp, labeled "T/M" and illuminates all three
lamps simultaneously to assure the lamps (internal and external) are in working order. TST does not activate
MM autopilot sense output. Releasing the button returns to the last sensitivity.
Pressing the marker mode select (“T/M”) for one second, while beacon audio is active, will also cause the
marker audio to mute for that beacon. The next beacon received will re-activate the audio.
The marker beacon receiver audio volume can be adjusted from the user setup menu (see
).
3.7.1
Marker Beacon Sensitivity
Press and hold the MKR button for about two seconds, until
the letter
H
appears in the OLED display, indicating that
the Marker beacon sensitivity is in the High Sense Mode.
Repeat to switch back to Low Marker Sense (“H” disap-
pears.)
Intercom Operation (8)
3.8.1
IntelliVox® Intercom VOX-Squelch
No adjustment of the
IntelliVox
® squelch control is necessary. Through three individual signal processors,
the ambient noise appearing in all six microphones is constantly being sampled. Non-voice signals are
blocked. When someone speaks, only their microphone circuit opens, placing their voice on the intercom.
The system is designed to block continuous tones; therefore, people humming or whistling in monotone may
be blocked after a few moments.
For consistent performance, any headset microphone
must
be placed within ¼-inch of your lips, preferably
against them. (ref:
RTCA/DO-214, 1.3.1.1 (a
)).
