Beam Steering and Attenuator Circuits

The beam steering circuits send the signals to the four antenna elements. During transmit, the beam steering circuit controls the phase relationships of the four RF outputs. The whisper/ shout attenuator makes the output power smaller or larger based on the control signals from the transmitter.

During receive, the phase of the received signals is different in each element. These beam steering circuit sends the signals to the receiver.

The TCAS computer receives a discrete input from the landing gear lever switch. When the landing gear lever is down, the TCAS computer uses all four antenna elements equally for the bottom antenna. Thus, the bottom antenna operates as an omnidirectional antenna.

BITE

The TCAS computer has BITE. The BITE continuously monitors TCAS for system faults and interface faults during normal operation. Also, when you start a self-test, the BITE makes test signals and sends them to the signal processor and receiver/ transmitter circuits. The BITE monitors 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. It also goes to the I/O circuits for output to the CDS DEUs and the FDAU.

When the BITE detects a fault during a self-test, the fault data goes to the I/O and then to these systems:

· DEUs

· REU* FDAU

· TCAS computer status LEDs if test is done from computer front panel.