Cirrus SR22 Pilot Operating Handbook page 204

Section 7 Cirrus Design
Airplane Description SR22
autopilot to allow NAV/LOC/GPS course tracking or to track a preset
heading.
The HSI incorporates conventional warning flags. The HDG (Heading)
flag will be out of view whenever the instrument is receiving sufficient
electrical power for operation. The NAV (Navigation) flag will be out of
view when a VOR or LOC frequency is tuned in the NAV1 receiver and
a reliable signal is present. The GS (Glideslope) flag will be out of view
when an ILS frequency is tuned on the Nav 1 receiver and a reliable
GS signal is present.
The NSD-1000 HSI is electrically driven and a red GYRO flag
indicates loss of electrical power. Redundant circuits paralleled
through diodes at the indicator supply DC electrical power for gyro
operation. 28 VDC for the redundant power circuits is supplied through
the 5-amp HSI 1 circuit breaker on the Essential Bus and 5-amp HSI 2
circuit breaker on Main Bus 2.
Serials with Avionics Configuration B - 0002 through 1601, 1603
through 1643 and 1645 through 1662 without PFD: The Sandel
SN3308 combines the functions of an HSI, an RMI, a full color moving
map, a Stormscope display, GPS annunciator, and 3-light marker
beacon indicators. Compass information is derived from a remote
directional gyro and a flux detector. Redundant power sources provide
28 VDC for system operation. Power is supplied through the 5-amp
HSI #1 circuit breaker on the Essential Bus and the 5-amp HSI #2
circuit breaker on Main Bus 2. Either circuit is capable of powering the
Navigation Display.
The full-color display uses a rear-projection system driven by an active
matrix LCD display. The unit uses a halogen lamp as the singular
primary display projection light source. A separate dimming knob for
the display brightness is provided immediately below the display.
The HSI display shows heading and navigation information in a 360°
view similar to a conventional mechanical HSI, or in an EFIS 90° ARC
view. This includes compass card, heading bug, course pointer,
course deviation bar, TO/FROM indicator, glideslope indicator, and
flags. Heading bug and course pointer settings include digital readouts
that make it easy to set precise headings and courses. One button
operation allows primary navigation to be selected from up to four
different sources: two VOR/ILS receivers and two GPS receivers.
Either GPS1 or NAV1 may be selected as primary navigation sources.
7-30 P/N 13772-001
Revision A5