TOP ATC ANTENNA (STA 610)
ELECTRONIC EQUIPMENTRACK, E2
RIGHT ATC
TRANSPONDER (E2-2)
SEE B
LEFT ATC TRANSPONDER (E2-3)
SEE B BOTTOM ATC
ATC ANTENNA RF ANTENNATRANSFER RELAYS (E2-3)
(STA 570) SEE C
TRANSPONDER CODE
SELECT  IDENTIFICATION
DISPLAY
SWITCH  SWITCH
MODE SWITCH
CODE
CODE
SWITCH
ATC CONTROL PANEL
SWITCH
A
TRANSPONDER PASS
LIGHT (GREEN) FWD
TRANSPONDER FAIL
LIGHT (RED)
CONTROL PANEL-INPUT
FAIL LIGHT (RED)

TOP ANTENNA FAIL
LIGHT (RED)
BOTTOM ANTENNA
FAIL LIGHT (RED)

ALTITUDE-INPUT
FAIL LIGHT (RED)

TEST SWITCH
ATC ANTENNA RF TRANSFER RELAY C Air Traffic Control System - Component Location Figure 1
G33086
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A
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 (3)  
The desired 4-digit airplane identity code is set with the code switches.

 (4)  
The desired altitude reporting condition is set with the altitude reporting switch or mode switch.

 (5)  
If the altitude reporting function is on, then the ATC system will reply to mode-A and mode-C ground station interrogations. If the altitude reporting function is off, then system will reply to mode-A interrogations. Mode-S replies are not affected by the condition of the altitude reporting function.

 (6)  
The four-digit identity code and mode configuration information is sent to the transponders through ARINC 429 buses and discretes. The 4-digit code identifys the airplane to the ground station for mode-A and mode-C interrogations.

 (7)  
When the airplane leaves the ground, the AIR/GND relay is set to AIR. This sends a discrete signal to the control panel. The control panel then sends an 'ON' discrete to the set transponder. At this point, the system will respond to ground station interrogations.

ALL TIME IN
MODE A
. SECONDS

P3
MODE C P2 PULSE MUST BE 6dB LESS IN AMPLITUDE RELATIVE TO P1 AND P3 PULSES FOR A VALID INTERROGATION.

Ground Station Interrogation
Figure 2

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 B. Mode-S Operation
 (1)  Mode-S functions operate on an airplane if the mode-S programming plug is configured with a unique mode-S address. If all the programming pins are grounded (they have a bit value of zero), then there is no unique address and the mode-S functions do not operate. The mode-S code is hard wired on mode-S equiped airplanes. The four-digit identity code set on the ATC control panel has no effect on the mode-S address code of the airplane. Mode-S functions in the airplane are automatic and are not configured by the pilot.
 C. Self-Test Operation
 (1)  
Both ATC transponders have Built-In Test Equipment (BITE). A BITE test can be started if the transponder to be tested has power. The BITE test is started when the TEST switch on the transponder front panel is pushed. The BITE test does the following:

 (a)  
Does a checksum of internal ROM contents

 (b)  
Tests the transponder RAM

 (c)  
Simulates noise sources and monitors the results

 (d)  
Tests the antenna impedance

 (e)  
Simulates a Mode-S All-Call interrogation and reply

 (f)  
Samples the internal power supply monitor

 (g)  
Checks the operation of the serial busses connected to the transponder.

 (2)  
The green XPDR PASS indicator light will come on if no errors were detected during the BITE test. The red XPDR FAIL indicator light will come on if any part of the BITE test fails.

 (3)  
　
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