The instrument switching module on the P5 overhead panel provides discretes to the display electronics unit (DEU) for display switching when you move the switch to the both on 1 or both on 2 position.
With the switch in the both on 1 position, the DEU’s use VOR data from VOR/MB receiver 1 for display. With the switch in the both on 2 position the DEU’s use VOR data from VOR/MB receiver 2 for display.
The instrument switching module also sends discretes to the FCC when you move the switch out of the normal position.
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