Discrete Output; Uat Status Output; Tx Suppression Output; Time Mark Input/Output - FreeFlight ADS-B FDL-978 Series Installation Manual

ADS-B FDL-978 Series and
Lite Series Installation Manual
Document No. 87343 Rev G

2.5.8 Discrete Output

Refer to SECTION 9 for a wiring diagram reference.
Two discrete outputs are available to provide UAT status and operational information to other
equipment. The two discrete output connection pins are as follows:
PIN SIGNAL
J1-28 TX SUPPRESS
J1-41 UAT 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 TC978) typically provides annunciation. This
discrete can be used to drive an annunciator when a display or TC978 is not
installed or capable of displaying 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-978 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-978-XVR.
2-12
Discrete Outputs
ELECTRICAL I/O DESCRIPTION
Vin -1.5V O L-Band Suppression Bus
Open/Ground O ADS-B Status
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