BendixKing MST 67A - Manual (Page 20)

PS 550 TRANSPONDER CONTROL UNIT
PS 550 Single or Dual Mode S Control Unit (Dual Unit shown).
PS 550 CONTROLS AND DISPLAYS
The PS 550 Control Unit is the master control for the transponder.
The PS 550 will also display the selected 4096 ATC code and current
mode of operation in the display window. Versions are available to
control one or two transponder. A “Fail” annunciation indicates failure
of the selected transponder, antenna or control data.
Note: If the PS 550 is interfaced to a MST 67A Mode S transponder
and the MST 67A senses a failure, a failure annunciation will be shown.
A maintenance check should be performed.
006-18301-0000 Rev 0 Effective Date 7/04 16
Controls and Displays
The Display Window displays the ATC
code selection, whether transponder #1
or #2 is active, transponder mode,
transponder ident and own aircraft flight
level (in TEST).
All display annunciations are seen during
the control unit self-test.
The 1/2 push button selects No. 1 or No.
2 as the active transponder. The other
unit is placed in standby. The Display
Window shows which transponder is the
active source.