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Page Title:
FUNCTIONAL OPERATION. |
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|  TM 11-4920-296-14&P
2-17. Table 2-4 lists the specific inputs/
2-13. In the Mode 4 self-test, the KIR-1A
may, or may not be connected to the test
outputs of the test set and their pertinent
set. With the KIR-1A connected, signals
characteristics.
are routed from the test set to the Interro-
FUNCTIONAL OPERATION.
2-18.
gation Computer in a manner similar to ac-
tual Mode 4 system operation. If the KIR-1A
2-19. Figure 2-3 shows the functional block
is not connected during the Mode 4 self-test,
diagram of the test set. This set consists of
the test set supplies signals which effectively
two major sections; the digital section (com-
test its own Mode 4 circuits.
posed of four nonreparable solid-state mod-
ules) and the rf section (composed of rf
2-14. The preceding discussion describes
module Al and its three nonreparable rf-
the general basic system-testing operation
type subassemblies).
of the test set. The test set checks three
types of transponders; namely, single-
2-20. Circuit operation occurs in two basic
channel, diversity-type, and lobing systems.
cycles; encode, and decode. During each of
For all types of systems, any mode may be
these cycles, signals are timed (clocked) by
selected for test. In addition to MODE
internal clock signals, whose frequency
selection, the test set controls the FUNC-
varies according to the cycle of operation.
TION to be tested. Functions include; sys-
Basic signal timing is derived from an inter-
tem testing (basic); VP; emergency; lamp-
nal 22-MHz oscillator, whose output is
testing; and frequency/power checks.
counted-down to the required CLOCK rate.
During SIF interrogation modes (in the en-
2-15. When the test set is first energized,
code cycle), the CLOCK rate is 1 MHz; for
the FUNCTION switch is placed in its SELF-
TEST position. This exercises the test set
Mode 4 interrogation the CLOCK rate is 555
kHz. During the decode cycle of operation,
circuits, and yields an ACCEPT indication
the CLOCK rate changes to 690 kHz for the
(lamp lights) if all circuits are operating
SIF mode replies (or remains at the 555 kHz
correctly. Once the self-test has established
rate for the Mode 4 replies).
correct test set operation, system-testing
operations can be accomplished, knowing
2-21. During the encode cycle, the digital
that a REJECT indication (lamp lights) must
circuits generate coded output pulse sets,
be caused by incorrect operation of the
whose timing and coding are determined by
transponder.
the front panel control settings. These dig-
ital signals are then fed to the rf module
2-16. The test set SLS pulse control en-
circuits, where they gate (modulate) rf
ables the operator to check the transponder
oscillator stages to produce output interro-
for proper response in the presence or
gation rf pulses (at 1030 MHz). Timing of
absence of the SLS pulse.
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