User's Manual

SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 4−55
15 Dec 2005
Table 4−9. RCZ−852 Diversity Mode S Transponder Interface Descriptions (cont)
Connector Pin
Designation
Functional Description
J1−73 SQUAT SWITCH 1 (NO) DISCRETE INPUT:
This discrete input is used in conjunction with SQUAT SWITCH 2 discrete input (pin 75).
The squat switch inputs tell the transponder if the aircraft is on the ground or in the air.
The two inputs have different affects on transponder operation, and the status of the two
are combined. SQUAT SWITCH 1 (NO) causes the transponder to indicate the in the air/
on the ground condition in replies to interrogations. SQUAT SWITCH 2 (NO) in addition
to performing the function of SQUAT SWITCH 1 (NO), also inhibits replies to ATCRBS,
ATCRBS/Mode S All−Call, and Mode S All−Call interrogations when the aircraft is “on the
ground”. The air/ground polarity is set by the SQUAT SWITCH POLARITY strap. The
matrix that follows, shows how the discretes affect the transponder operation:
Squat Sw Transponder Operation
Polarity Squat Switch Inputs Air/Ground ATCRBS/All−Call
Strap 1 (NO) 2 (NO) Status Replies
Gnd Gnd Gnd On Ground Disabled
Gnd Gnd Open On Ground Enabled
Gnd Open Gnd On Ground Disabled
Gnd Open Open In Air Enabled
Open Gnd Gnd In Air Enabled
Open Gnd Open On Ground Disabled
Open Open Gnd On Ground Enabled
Open Open Open On Ground Disabled
J1−74 XPDR OFF (NO) INPUT:
This discrete input is used to turn the transponder power supply OFF. It should not be
connected in aircraft installations.
J1−75 SQUAT SWITCH 2 (NO) DISCRETE INPUT:
See pin 73.
J1−80 thru 85
J1−94 thru 98
ENCODING ALTIMETER NO. 2 ELEVEN BIT INPUT:
Transponder input from Encoding Altimeter No. 2. These eleven (11) lines from the
altitude encoder comprise an 11−bit word representative of the aircraft altitude.
J1−90 XPDR STRAP +5 VOLT OUTPUT:
Connect Strap Board connector pin W1P1−3 (red wire) to J1−90. This output pin
provides the +5 volt input power required by the Strap Assembly.
J1−91 XPDR STRAP CLOCK (N) OUTPUT:
Connect Strap Board connector pin W1P1−6 (blue wire) to J1−91. This output consists of
48 clock pulses that serially shift the system options data out of the Strap Assembly shift
registers.
J1−92 XPDR STRAP LOAD (N) OUTPUT:
Connect Strap Board connector pin W1P1−2 (orange wire) to J1−92. This output is used
to load the system options status into the Strap Assembly shift registers during initial
system power−up.