(b)  
Remove the screws that attach the VOR/LOC rf power divider to the airplane.

 TASK 34-31-07-404-013
 3.  VOR/LOC RF Power Divider Installation_____________________________________
 A.  General
 (1)  There are three VOR/LOC rf power dividers installed in the E1 electronics equipment rack in the main equipment center. They are installed on the left end of the No. 6 shelf. The equipment numbers are B8316 for the left, B8317 for the right, and B8318 for the right/center rf power dividers.
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747-400
MAINTENANCE MANUAL

 (2)  The installation procedures are the same for each VOR/LOC rf power divider.
 B. References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 34-31-00/501, Instrument Landing System

 (3)  
IPC 34-31-55 Fig. 1

 C. Access
 (1)  Location Zone
 117 Electrical and Electronics Compartment, LH

 D. Procedure
 S 424-014
 (1)  Install the VOR/LOC rf power divider:
 (a)  
Align the VOR/LOC rf power divider to the holes in the No. 6 shelf

 (b)  
Install the screws to attach the VOR/LOC rf power divider to the shelf

 (c)  
Connect the coaxial cables to the VOR/LOC rf power divider and hand tighten them.

 S 714-015
 (2)  Test the VOR/LOC rf power divider:
 (a)  
Do the Prepare for the System Test and the Localizer parts of the System Test for the ILS (AMM 34-31-00/501).

 (b)  
Do the Prepare for the System Test and the System Test for the VOR navigation system (AMM 34-51-00/501).

 S 864-016
 (3)  If electrical power is not necessary, do this task to remove electrical power: Manual Control (AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 MARKER BEACON SYSTEM - DESCRIPTION AND OPERATION
________________________________________________
 1.  General_______
 A.  The marker beacon system provides visual and aural annunciations when the airplane flies over ground based marker beacon transmitters. The different transmitter stations include airways,inner,middle and outer markers.
 B.  The system consists of a marker beacon receiver module and an antenna. The system receives 115-volt ac power from the standby bus.
 C.  The marker beacon ground stations all transmit a 75 MHz signal that is modulated by one of four audio signals, depending on the type of marker beacon. The marker beacon receiver detects the modulated audio signal and provides these audio tones to the flight interphone system. The frequency of the audio signal determines which marker beacon annunciation (IM, MM, OM) is displayed on the primary flight display (PFD).
 D.  The four types of marker beacons with their tone frequency and the colored alphabetical annunciations on the PFD are as follows:
 (1)  
Airways marker - A 3000 Hz tone keyed with a Morse Code identifier and a white flashing IM annunciation.

 (2)  
Inner marker - A 3000 Hz tone keyed as continuous dots and a white flashing IM annunciation.

 NOTE: A back course marker is located at the opposite
____ end of the runway from the inner marker and is also identified by a white flashing IM annunciation only the 3000 Hz tone is keyed as continuous paired dots.
 (3)  
Middle marker - A 1300 Hz tone keyed as alternate dots and dashes and a yellow flashing MM annunciation.

 (4)  
Outer marker - A 400 Hz tone keyed as continuous dashes and a cyan flashing OM annunciation.

 2.  Marker Beacon Receiver Module_____________________________
 A.  A marker beacon receiver module is installed in each VOR/MKR receiver. The marker beacon module in the left VOR/MKR receiver is enabled and the marker beacon module in the right VOR/MKR receiver is inhibited.
　
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