*
Send TCAS aurals to the warning electronic system (WES)

*
Transmit coordination data to traffic airplanes with TCAS.

Air/Ground Relay
This discrete from the air/ground relay supplies in-air or on-ground status to the TCAS computer. The air/ground discrete inhibits resolution advisories (RAs) when the airplane is on the ground and inhibits tests when in the air. Also, the air/ground discrete increments flight legs in the TCAS nonvolatile memory when the central maintenance computing system (CMCS) fails.
GPWC -Advisory Delay Discretes
The GPWC sends a discrete to the TCAS computer to inhibit TCAS advisories during some ground proximity warning conditions.
PSEU -Landing Gear Position
This analog discrete from the PSEUs supply the TCAS computer with the position of the landing gear. When the TCAS computer gets this discrete, the TCAS computer makes the bottom directional antenna become an omnidirectional antenna.
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TCAS -POWER, ANTENNAS, ANALOG DISCRETE INTERFACES AND PROGRAM PINS

Suppression Input/Output
The TCAS computer gets a suppression pulse when an ATC transponder or DME interrogator transmits. When the TCAS computer transmits, it sends a suppression pulse to the ATC transponders and the DME interrogators.
WEU -TCAS Aurals -Voice Outputs
The TCAS computer sends RA and TA aural signals to the warning electronic units (WEUs). The WEUs amplify the RA and TA aurals and send them to the aural warning speakers to alert the flight crew.
WXR -TCAS Alert Inhibit
The TCAS computer gets an inhibit discrete from the predictive windshear (PWS) function of WXR. When there is a PWS alert, this discrete does these functions:
*
Changes TCAS resolution advisories (RAs) to traffic advisories (TAs)

*
Inhibits TCAS aural alerts.

Program Pins
These are the functions that the program pins on the TCAS computer enable:
*
A self-test inhibit to prevent self-test in the air

*
The audio level of the voice outputs

* TCAS advisories. The 16,000 FT and the 32,000 FT program pins enable climb advisories up to an altitude of 48,000 feet.
EFFECTIVITY BEJ ALL  34-45-00 
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TCAS -POWER, ANTENNAS, ANALOG DISCRETE INTERFACES AND PROGRAM PINS

EFFECTIVITY BEJ ALL  34-45-00 
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TCAS -DIGITAL INTERFACES

General
The TCAS computer has digital interfaces with these units:
*
Left ATC/Mode S transponder

*
Right ATC/Mode S transponder

*
Left radio altimeter transceiver

*
Right radio altimeter transceiver

*
Left AIMS cabinet

*
Right AIMS cabinet.

ATC/Mode S Transponder -Control and Coordination Data
The dual transponder panel sends this control data through the selected ATC/Mode S transponder to the TCAS computer:
*
TCAS mode selection (TA only or TA/RA)

*
Control of the altitude limits for the TCAS display that shows on the ND.

For the TCAS computer to calculate coordination data, ATC transponder sends this data to the TCAS computer:
*
24-bit airplane address

*
Barometric altitude

*
Maximum true airspeed.

The TCAS computer sends this data to the transponder:
*
General TCAS operational status

*
Mode S coordination data.

Radio Altimeter Inputs
The TCAS computer gets radio altitude from the left and right radio altimeter transceivers.
TCAS Inputs from AIMS
The left AIMS cabinet supplies these inputs to the TCAS computer:
*
Inertial reference unit (IRU) data from the air data inertial reference system (ADIRS).

*
Data loader data

*
Data loader enable analog discrete

*
Central maintenance computing system (CMCS) data.

The right AIMS cabinet does not supply any inputs to the TCAS computer.
TCAS Outputs to AIMS
The TCAS computer sends TCAS data load status to the left AIMS cabinet.
The TCAS computer supplies these outputs to both AIMS cabinets:
*
Traffic advisory (TA) and resolution advisory (RA) data, which includes all traffic data for TCAS displays

*
TCAS maintenance data.

EFFECTIVITY BEJ ALL  34-45-00 
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777 AIRCRAFT MAINTENANCE MANUAL

TCAS -DIGITAL INTERFACES

EFFECTIVITY BEJ ALL  34-45-00 
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D633W101-BEJ  Jan 05/2002 
　
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