Ilf 404, 405, 410, 414-417, 422-429, 451, 501-509, 510-517, 519,

520-527, 536, 541, 542, 551

· Weather radar

· DME/ATC/TCAS suppression coax tees

· Display electronic unit (DEU) 1 and 2

· Remote electronics unit (REU).

Program pins control the configuration of the TCAS computer.

Power

The TCAS computer gets 115v ac from AC transfer bus-1 through the TCAS circuit breaker on the P18 circuit breaker panel.

Antennas

There are two TCAS directional antennas. The TCAS directional antennas receive traffic airplane reply signals. They also transmit the TCAS interrogation signals.

Landing Gear Lever Switch

The discrete from the landing gear lever switch tells the TCAS computer that the landing gear is down. When the TCAS computer gets this discrete, the TCAS computer makes the bottom directional antenna become an omnidirectional antenna.

PSEU

The discrete from the PSEU supplies in-air or on-ground status to the TCAS computer. The air/ground discrete inhibits TCAS operation on the ground and inhibits tests when in the air. The air/ground discrete also controls flight leg increments in the TCAS nonvolatile memory.

GPWC - Advisory Inhibit Discretes

The GPWC sends one discrete to the TCAS computer. This discrete inhibits TCAS aural and visual warnings when the GPWC makes any voice message.