RT-1296/APX-100(V)1(IFF) and RT-1557/APX-100(V)1(IFF) Control and Indicator
MODE 4 CODE
Selects condition of code changer in remote computer.
Selects mode 4 code setting for present period.
Selects mode 4 code setting for succeeding period.
Retains mode 4 code setting when power is removed from transponder.
Determines whether Mode 4 is on, off, or in BIT operation.
MODE 4 AUDIO/
Enables or disables audio and visual Mode 4 indicators. Visual indicators signify valid replies.
Audible signal indicates the interrogation and reply computers are set to opposite codes.
Enables TEST mode.
Indicates that BIT or MON failure is due to altitude digitizer.
Indicates that BIT or MON failure is due to external computer.
Indicates that BIT or MON failure is due to high voltage standing wave ratio (VSWR) in
MODE 4 REPLY
Indicates that a Mode 4 reply is generated.
Controls transmission of I/P pulse.
MODE 1 Selector
Selects Mode 1 code to be transmitted.
MODE 2 Selector
Selects Mode 2 code to be transmitted.
MODE 3/A Selector
Selects Mode 3/A code to be transmitted.
Due to possible operating problems of
the (IFF), usage of the UHF radio on fre-
quency ranges 341.325 thru 345.325 is
prohibited while operating the IFF in
a. Starting Procedures.
If the MODE 2 code has
not been set previously, loosen two screws which hold the
MODE 2 numeral cover, and slide the cover upward to ex-
pose numerals of MODE 2 code switches. Set these
switches to code assigned to helicopter. Slide cover down
and tighten screws.
1. MASTER control switch STBY. Allow 2 min-
utes for warm up.