Frequency Transfer Switch

The frequency transfer switch on the NAV control panel permits the crew to transfer the frequency from the standby display window on the NAV control panel, to the active display window. The transfer switch is a momentary action switch. When you push the switch, it changes the discrete level to the FCCs. The discrete tells the FCC when there is an ILS frequency change.

Navigation/Displays Source Select Panel

The VHF NAV switch on the navigation/displays source select panel is a three position switch. The positions are; BOTH ON 1, NORMAL, and BOTH ON 2. This switch changes the source of the data that the DEUs use for the ILS displays.

In the NORMAL position, MMR 1 supplies data for the captain displays and MMR 2 supplies data for the first officer displays. When you select BOTH ON 1, the DEUs use MMR 1 as the source for the captains displays and first officers displays.

When you select BOTH ON 2, MMR 2 is the source for the captains displays and first officers displays.

Discrete signals also go to the flight control computers (FCCs) to signal that the switch is not in the normal position.