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MAINTENANCE MANUAL
CAS-100 COLLISION AVOIDANCE SYSTEM
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Table 19. CTA-81B Control Unit Controls and Indicators
Control/Indicator
(See Figure 11)
Function
Function Selector Switch
Rotary switch. Controls operating modes of one Mode S
transponder (ATC 1 positions) and one ATCRBS
transponder (ATC 2 positions). Requests TCAS operating
modes
(NOTES 1. and 2.)
ATC 1 TEST Position
Holding the switch in spring-loaded TEST position for one
second starts the TCAS and Mode S transponder
Functional self-test. If TCAS processor Functional Test
Inhibit program pin is strapped, TCAS functional test is
prevented while the aircraft is airborne. The TCAS flag
shows TCAS on the RA/VSI display during the functional
test (approximately 12 seconds). The traffic display shows
TEST. A test pattern shown on the traffic display lets
verification of each type of intruder symbol. During the first
three seconds of the functional test, a lamp test is done on
all segments of the RA/VSI. If a failure is found during
functional test, the TCAS flag continues to show TCAS.
Following the lamp test, a set test command is shown until
end of test.
ATC 1 STBY Position
The ATC 1 STBY position puts the Mode S transponder,
ATCRBS transponder, and TCAS in STANDBY mode. The
Mode S transponder power is applied, but does not
transmit squitters or reply to interrogations in STANDBY
mode. In STANDBY mode, all TCAS broadcast,
surveillance, and tracking operations are made
unserviceable and the traffic display is erased but for a
TCAS STBY annunciation. The ATCRBS transponder is
on in STANDBY mode, but does not respond to
interrogations.