Sandel ST3400, Installation Manual

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3 INTERFACE FUNCTIONS
3.1 Dual Inputs
The ST3400 contains two sets of inputs for each equipment type; for instance,
there are two sets of heading inputs. In general (with some exceptions) the
“primary” inputs are on P1 and the “secondary” inputs are on P2. Secondary
inputs are always optional.
The ST3400 does not contain any internal comparator functions to compare the two
sets of inputs. However, it will revert to the secondary input if the primary input
flags or fails. This feature may be helpful to improve the system reliability of an
aircraft installation. If the #1 inputs fails (such as FMS1 failure) the #2 input will
become operational within 5 seconds of the failure; typically within 2 seconds.
3.2 Power
The primary two-wire power is 28 volt dc on J-3 and is supplied from the aircraft
avionics buss through a circuit breaker. Ground is provided on J-3 and should be
attached to an approved airframe ground.
Two 26 volt 400hz excitation inputs are available, if required. One is located on J-
1 and the other on J-2. They are labeled as inverter-1 and inverter-2. All signals
on J-1 that require excitation must use the same excitation as the inverter-1 input.
All signals on J-2 (if used) that require excitation must use the same excitation as
the inverter-2 input. If the installation of the ST3400 does not use any XYZ
(ARINC407) signal sources, the inverter inputs are not required and should be
grounded.
3.3 External Annunciators
Optional external annunciator lamp discrete outputs are available to drive TAWS
INH, FLAP OVRD, G/S OVRD, CAUT, WARN, annunciators on J-3. A 6
th
annunciator output can be selected to be either TCAS INH (activates on either
Caution or Warning), GPWS FAIL which duplicates the on-screen GPWS FAIL
annunciation, TCAS IND which is discrete feedback to TCAS processors when
the ST3400 is used as the primary TCAS indicator, or AUDIO ENA which may
be used to activate a relay whenever ST3400 audio is present, including
maintenance test audio.
TAWS INH is a switch /annunciator and performs the same function as the on-
screen TAWS INHIBIT function. FLAP OVRD is a switch /annunciator and
performs the same function as the on-screen FLAP OVRD function. G/S OVRD
is a switch /annunciator and performs the same function as the on-screen
G/S OVRD function.
These circuits are capable of sinking a maximum of 250 milliamps to ground and
can drive incandescent lamps. Dimming of the external annunciators is
accomplished by sourcing the annunciators from the aircraft day/night bus.
82002-IM-L ST3400 INSTALLATION MANUAL
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