Operating instructions

202-890-0402 Rev. 2 Page 9 Oct. 2010 PMA8000B Pilot Guide
Marker Beacon Operation (10)
The Marker Beacon
Receiver uses visual
and audio indicators
to alert you when the
aircraft passes over a
75 MHz transmitter.
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 cou-
pled with a 1300 Hertz tone. It is keyed alternately with short 'dot' and
long 'dash' bursts at 95 combinations 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.
The audio from the Marker Beacon Receiver can be heard by select-
ing the "MKR" push-button switch. To adjust the volume level, there
is a service adjustment located on the top of the unit.
A pushbutton is used to set the receiver sensitivity and to test the indi-
cator lamps mute the marker audio.
Use "HI" sensitivity initially. This allows you to hear the outer
marker beacon about a mile out. Then touch the smaller MKR button
to switch into Low Sensitivity mode. “LO” sensitivity gives you a
more accurate location of the Outer Marker. Holding the MKR button
for one second activates marker test lamp, labeled "T/M" and illumi-
nates 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 will also
cause the marker audio to mute for that beacon. The next beacon re-
ceived will re-activate the audio.
Internal Recorder System
The Intercom Recording System is a digital recording system allow-
ing automatic storage and playback of aircraft radio traffic.
Operating as a continuous loop recorder, (first message received will