ADS-B FDL-DB Dual Band Series
Installation Manual
Document No. 88552 Rev A
2-26
FFS Copyright © 2020 All rights reserved.
2.5.8 Discrete Output
Two discrete outputs are available to provide UAT status and operational information to other
equipment. The two discrete output connection pins are as follows:
Discrete Outputs
PIN
SIGNAL
ELECTRICAL
I/O
DESCRIPTION
J1-34
TX SUPPRESS
Vin -1.5V
O
L-Band Suppression Bus
J1-53
UAT STATUS
Open/Ground
O
ADS-B Status
2.5.8.1 UAT Status Output
Failure status of the UAT as well as loss of UAT position data must be annunciated
to the pilot. The connected display or control head, such as the TC978, typically
provides required failure annunciation. This discrete can be used to drive an
annunciator when a display or TC978 is not installed or the MFD is not capable of
annunciating status The UAT Status output is an active low, open collector output
capable of sinking a maximum of 100 mA. The UAT status output indicates a UAT
transmit or receive system failure when continuously grounded. UAT status output
also indicates the loss of valid GPS data from an internal or external GPS. If the
internal or external GPS is not functioning, reporting a failure, or reporting invalid
GPS position data, this discrete will toggle between ground and open at a rate of
approximately four times per second.
2.5.8.2 TX Suppression Output
The TX Suppress output is for suppressing other L-band equipment during UAT transmissions.
TX Suppress outputs a high (Vin
– 1.5 V) only during UAT ADS-B message transmissions and
is low otherwise. The TX Suppress output is typically connected to the transponder suppression
bus.
Receiver only installations do not need to connect to the transponder suppression
bus.
2.5.9 Time Mark Input/Output
For the FDL-DB Dual Band Series, the Time Mark Input/Output is an RS-422 differential pair
conforming to the ARINC 743A/B specification for the one pulse-per-second (PPS) input from
an external GPS or output when the Transceiver/Receiver has an internal GPS. The Time Mark
input/output from a GPS provides the timing synchronization for sending ADS-B messages.
Time Mark from a GPS provides timing synchronization for ADS-B transmit
messages. The Time Mark from an external GPS MUST be synchronized to UTC
second epoch to operate correctly with the FDL-DB-XVR.
Time Mark inputs from a single ended PPS source (e.g. Garmin Series 400/500
GPS) must be properly interfaced to the differential interface for reliable operation.
