General. The multi-mode receivers (MMRs) get RF inputs from these antennas:

The multi-mode receivers (MMRs) get RF inputs from these antennas:

· VOR/LOC antenna on the vertical stabilizer

· Localizer antenna in the nose radome

· Glideslope antenna in the nose radome.

The VOR/LOC antenna RF inputs go through the power dividers then to the localizer (LOC) antenna (ANT) switches.

The localizer antenna RF inputs go directly to the LOC ANT switches. The antenna switches select the VOR/LOC antenna or localizer antenna as the source of the localizer RF signal input to the MMRs.

The glideslope antenna inputs do not go through the antenna switches. Glideslope antenna RF inputs go directly to the MMRs.

When you tune an ILS frequency on the navigation (NAV) control panels, they send 28v dc to the LOC antenna switches. The LOC ANT switches use 28v dc from the NAV control panels and a discrete signal from the integrated flight system accessory unit (IFSAU) for operation.

The IFSAU sends the discrete when it receives a discrete from the Flight Control Computers (FCCs). The FCCs send the discrete when you select the approach (APP) or localizer (LOC) mode on the DFCS mode control panel.