User's Manual
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 4−45
15 Dec 2005
Table 4−8. XS−950 Data Link Transponder Interface Descriptions (cont)
Connector Pin
Designation
Functional Description
P1A−5A,
P1A−5B,
P1A−5C,
P1A−5D
MAXIMUM TRUE AIRSPEED PROGRAM INPUTS:
The Maximum True Airspeed inputs are used for strapping the maximum cruise airspeed
capability of the aircraft. The inputs use ground/open logic levels. The Max True
Airspeed Common (pin P1A−5D) can be used to supply a ground.
Program Pin
P1A−5A P1A−5B P1A−5C Definition
Open Open Open No Maximum Airspeed Available
Ground Open Open Maximum Airspeed ≤75 Knots
Open Ground Open Maximum Airspeed >75 and ≤150 Knots
Ground Ground Open Maximum Airspeed >150 and ≤300 Knots
Open Open Ground Maximum Airspeed >300 and ≤600 Knots
Ground Open Ground Maximum Airspeed >600 and ≤1200 Knots
Open Ground Ground Maximum Airspeed >1200 Knots
Ground Ground Ground Not Assigned
P1A−5E, 5F ARINC 429 TX COORDINATION BUS INPUT: (P1A−5E [A], P1A−5F [B])
Two high speed ARINC 429 busses (100K bits/second nominal) are provided to interface
between the transponder and a TCAS computer unit. The standards for this interface are
defined in ARINC Characteristic 735, “Traffic Alert and Collision Avoidance System”.
P1A−5G, 5H ARINC 429 XT COORDINATION BUS OUTPUT: (P1A−5G [A], P1A−5H [B])
See pins P1A−5E, 5F.
P1A−5J AIR / GROUND #2 DISCRETE INPUT:
This pin and AIR / GROUND #1 Discrete Input (pin P1A−5K) provide a method for the
transponder to automatically determine the Air/Ground status of the aircraft. The status is
used in replies to Mode S interrogations and to inhibit replies to certain types of
interrogations. Both inputs use ground/open logic, where a Ground specifies an “On the
Ground” condition and an Open specifies an “In the Air” condition.
When this pin is connected to the Air/Ground Relay (Squat Switch), the transponder will
not reply to ATCRBS, ATCRBS/Mode S All Call, or Mode S All Call when the input is set
for “On the Ground”. This input should be connected to the Air/Ground Relay for normal
operation.
P1A−5K AIR / GROUND #1 DISCRETE INPUT:
See pin P1A−5J.
When this pin is connected to the Air/Ground Relay (Squat Switch), the transponder
replies to all types of interrogations irregardless of the state of the input. This input allows
the transponder to reply during a ramp test.
P1A−6A, 6B FMC #1/Gineral In #2
This differential pair input supports common existing FMC configurations where flight ID is
available on the FMC General Purpose output bus but the other Enhanced data is only
available on a display bus.