Description (AMM 34-28-01)

A- The IRS transfer switch is situated on the P5 panel and controls IRS transfer relays 1 and 2, located on the E1-2 equipment shelf. These two relays transfer analog magnetic heading signals and valids from either DAA to the RDDMI's, and supply a ground to the EFIS SG's, the VSI's, and the weather radar R/T unit. The ground enables selection of the alternate IRU as the source for digital information to these components.

B- Interlock contacts on the IRS transfer relays prevent them both being switched out of their "NORMAL" position at the same time.

C- If the IRS transfer switch is moved from the NORMAL position, instrument switch annunciator lights (if installed) on the captain's and first officer's instrument panels will illuminate.