reply pulse will be transmitted through the
tion. The auxiliary equipment required for
limited operation of the RT-859/APX-72 con-
AT-884A/APX to the interrogating station.
sists of Antenna AT-884A/APX (or equiva-
b. Receiver-Transmitter, Radio RT-859/
lent), Control, Transponder Set C-6280(P)/
APX-72. The coded interrogating pulse input
APX and a 28 vdc or 28 vdc and 115 vac power
to the RT-859/APX-72 is tested for validity
source. Additional auxiliary equipment re-
and, if it conforms to the mode and code preset
quired for complete operation consists of Com-
in the RT-859/APX-72, a coded reply pulse
puter KIT-1A/TSEC, Pressure Altitude Digi-
will be generated and fed to the AT-884A/
tizer CPU-66/A (or equivalent) and Test Set,
APX for transmission, Modes 1, 2, and 3/A
Transponder Set TS-1843/APX.
interrogations are processed within the RT-
859/APX-72, but modes C and 4 interrogations
1-10. System Analysis
are applied to external equipment which gen-
Refer to block diagram (fig. 1-9) for this
erates the coded reply pulse for transmission
discussion of system analysis.
through the RT-859/APX-72. The RT-859/
APX-72 contains only the MODE 2 code setting
a. Antenna AT-884A/APX (or equivalent).
switch; all other controls including source
The mode 1, 2, 3/A, C, or 4 coded interrogating
power switch are on the C-6280(P)/APX.
pulse is received at the AT-884A/APX and fed
Additional reply responses for identification of
directly to the RT-859/APX72. If the interro-
position and emergency are available for trans-
gating signal is determined to be valid, a coded
MODE 1,2, 3/A,C OR 4
MODE 1,2,3/A,C OR 4
AND I/P OR EMER
Figure 1-9. System analysis, block diagram.