User's Manual Part 2

T
2
CAS / Part No. 9000000
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
34-43-20
15 Feb 2003
Use or disclosure of information on this page is subject to the restrictions in the proprietary notice of this document.
4--22
Table 4--1. TT--950/951/952 T
2
CAS Computer Unit Interface Description (cont)
Connector Pin
Designation
Functional Description
LBP--10 +28 Vdc Power Input (HI)
This pin along with the T
2
CAS computer unit +28 Vdc Power Return line (LBP--3) provide
the +28 Vdc power requirements for the T
2
CAS computer unit.
Wiring requirement is a standard #18 AWG.
NOTE: The T
2
CAS TT--950/--952 computer operates with either 115 V ac, 400 Hz, or
+28 Vdc input power and the TT--951 computer operates on +28 Vdc input
power only. On the TT--950/--952 computers, if +28 Vdc is used, the power
should be connected through a 10 Amp circuit breaker, and the pins for the 115
Vac input should be left unconnected.
LBP--11 Chassis Ground
Connect to aircraft frame. The T
2
CAS Chassis and signal ground pins should use the
same AWG as the power connections (See LBP--1 and LBP--10).
LBP--12 Mutual Suppression Pulse Bus Input
The T
2
CAS computer unit joins the mutual suppression bus daisy chained through TCAS
and other RF transmitting equipment on board the aircraft. The TCAS function receives
suppression pulses from other LRUs on this bus, which is used to suppress the TCAS
receivers during such transmissions. This prevents the TCAS function from interpreting
these transmissions as valid replies from an intruder aircraft. When not suppressed, the
TCAS function transmits its own suppression pulses on the same bus in order to
suppress the receivers in other L--band systems on the aircraft. The L--Band suppression
coax must be RG142, RG400, or equivalent coaxial cable which meets the operational
characteristics required by ARINC 735A.
LBP--13 GPS Antenna Port (Active on TT--952 and reserved for TT--950 and TT--951)
T
2
CAS unit TT--952 uses this pin for the GPS Antenna port -- RF input from the GPS
antenna and +12 Vdc output to power the active amplifier GPS antenna.
The minimum coax loss between the GPS antenna’s output and the T
2
CAS computer’ s
GPS input port is equal to the maximum preamplifier gain minus 29 dB. The maximum
coax loss between the GPS antenna’s output and the T
2
CAS computer’ s GPS input port
is equal to the minimum preamplifier gain minus 12.5 dB.
The Interface descriptions that follow are for the 53--pin Data Loader connector J1 mounted on the
front panel of the T
2
CAS computer unit. These descriptions are used to make up the cable that is
used to interface between the T
2
CAS computer unit and an ARINC 615 Portable Data Loader (PDL),
a RS--232 PC Serial Port, a RS--422 Flight Data Recorder, or an ARINC 429 Maintenance Display.
J1--1, 2 ARINC 429 PDL Bus Input: [J1 --1 (A), J1--2 (B)]
This differential pair input is a high--speed ARINC 429 bus (100k bits/second nominal)
that is used to input data from the data loader to the TCAS computer unit. The standards
for this interface are defined in ARINC 615 Airborne Computer High Speed Data Loader.
These pins should be connected to pins 1 and 2 of the PDL cable interface.
J1--3,
J1--4
Spare Pins