PS Engineering
PMA7000BT Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-780-0204
Page 3-8
Rev. 1, July 2015
3.9
Marker Beacon Operation
The optional 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 coupled 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 selecting the "MKR" push-button switch. To
adjust the volume level, there is a service adjustment located on the top of the unit.
A three-position switch is used to set the receiver sensitivity and to test the indicator lamps. Use "HI" sen-
sitivity initially. This a
llows you to hear the outer marker beacon about a mile out. Then select the “
LO
”
sensitivity to give you a more accurate location of the Outer Marker. The momentary down switch position
is marker test, 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 sense output.
Pressing the marker mode select down (to “T/M”) will cause the marker audio to mute for that beacon. The
next beacon received will re-activate the audio.