Avidyne IFD540 Pilot's Manual page 145

User Option Item Title
Com Frequencies Spacing
Advisory Glideslope
Auto-VLOC Tuning
GPS  VLOC Capture
AUX Pages 4-37
Description
25 kHz* - Com tuning will use
25 kHz spacing;
8.33 kHz – Com tuning will use
8.33 kHz channel spacing.
On* - Will transmit a glideslope
deviation signal for display on
external indicators (e.g. HSI,
EFIS) for approaches that don't
have a published glideslope
associated with them (e.g.
LNAV + V);
Off – Will not transmit
glideslope deviation data for
approaches that don't have a
published glideslope
associated with them.
On* - Enables the automatic
tuning of the active nav
frequency slot to follow the
governing navaid in the flight
plan. For example, if the next
FMS flight plan leg is a VOR,
this will automatically tune the
VOR frequency into the active
nav slot;
Off – Disables the automatic
tuning of the active nav
frequency into the active nav
slot.
Auto* - Allows the GPS 
VLOC state for nav source and
an automatic transition to
VLOC if the capture criteria are