*
Intermediate frequency (IF) video processor

*
Transmitter

*
Directional antenna

*
Beam steering.

I/O
The I/O circuit gets other on-board airplane systems data, such as these:
*
Magnetic heading, pitch and roll IRU data from the AIMS cabinets

*
Altitude from the radio altimeters

*
Coordination and control data from the ATC/Mode S transponder system

*
Landing gear down discrete from the PSEUs

*
Alert inhibit from the weather radar (WXR) receiver-
transmitters (RTs)

*
Aural inhibit discretes from the GPWC.

Use the MAT to load the operational software files into the TCAS computers.
Program pins enable altitude limits and audio volume control functions in the TCAS computer.
The I/O circuits send this data to the CPU.
CPU
The CPU gets the data from the inputs of the I/O and puts it into memory. The CPU combines the input data and the data received from the signal processor, the CPU makes calculations necessary for the TCAS displays and traffic advisories (TA) and resolution advisories (RA) aurals.
The CPU sends the AIMS cabinets TCAS display data to show on the NDs and PFDs. It also sends signals to the voice output circuits to make TCAS aurals.
EFFECTIVITY BEJ ALL  34-45-00 
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D633W101-BEJ  Sep 05/2002 

TCAS -TCAS COMPUTER -FUNCTIONAL DESCRIPTION

BITE
The TCAS computer has BITE that continuously checks TCAS for system faults and interface faults during normal operation. Also, when you start a self-test, the BITE makes signals and sends them to the signal processor and receiver/transmitter circuits. The BITE checks for system faults and interface faults during the self-test.
When the BITE detects a fault through the continuous fault monitor, the fault goes into the fault memory and also to the I/O circuits for output CMCS through the left AIMS cabinet.
When the BITE detects a fault during a self-test, the fault data goes to the I/O and to the CMCS and also to the status LEDs on the front panel.
Voice Output
When there is a TA, RA, or during a self-test, the TCAS computer sends signals to the voice output circuits. The voice output circuits send TA, RA, and test voice signals to the WEUs. The WEUs makes the TA, RA, and test aural messages and sends them to the aural warning speakers. During windshear, ground proximity warning, and ground proximity alert conditions, the GPWC sends analog discretes to the TCAS computer to inhibit TCAS advisories.
EFFECTIVITY
BEJ ALL

Suppression
The suppression circuits send a suppression pulse each time the TCAS computer transmits. The TCAS computer receives a suppression pulse when an onboard ATC/Mode S transponder or DME interrogator system transmits. This suppression pulse inhibits the TCAS computer receiver circuits.
Signal Processor
The signal processor gets bearing information from the IF/video processor and converts it into digital signals. The signal processor:
*
Uses bearing measurement logic and the bearing information to calculate the intruder airplane range and bearing

*
Detects the mode C or mode S pulses

*
Makes all signals necessary to receive and transmit mode S and ATCRBS interrogations through the receiver/transmitter circuits.

Receiver and IF Video Processor
The receiver has four individual sections, one for each element of the directional antenna. The receiver and the IF video processor combine the 1090 MHz received signals. The signal processor uses the four received signals from the receiver sections to calculate the bearing information and detect the mode C and mode S data pulses.
34-45-00

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TCAS -TCAS COMPUTER -FUNCTIONAL DESCRIPTION

Transmitter
The transmitter has a 1030 MHz output. The transmitter gets signals from the signal processor. It makes and sends four output signals to the beam steering circuits.
Directional Antenna
The directional antenna has four elements spaced 90 degrees apart. Each element is independent of the others and has it own coaxial connector.
Beam Steering Circuit
The beam steering circuits directs the antenna sensitivity during receive or transmit. During transmit, the beam steering circuit controls the phase relationships of four RF outputs for each antenna element. The different phases of the four transmit signals direct the RF beam.
During receive, the phase of the received signals are different in each element.
When the landing gear is down, the TCAS computer receives an analog discrete input from the PSEUs. The analog discrete makes the TCAS computer use only one beam steering output for the bottom antenna. The bottom antenna operates as an omnidirectional antenna.
　
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