User's Guide

DRAFT
Page 1-9
17 Mar 2016
23-15-87
SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
ARINC 781-500 SDU and SCM
© Honeywell International Inc. Do not copy without express permission of Honeywell.
A. TCP
The TCP is a device that uses an ARINC 429 interface per ARINC 739, which lets you communicate
with individual instruments on an aircraft, including the flight management system, very high
frequency radio, and the SDU.
B. 4-Wire Audio
The SDU supports two 4-wire audio interfaces.
C. Ethernet
The SDU supports two Ethernet data interfaces.
D. Maintenance Port
The SDU is equipped with a maintenance port, located on its front panel. The maintenance port
provides the physical connection to a password-protected Maintenance Port Utility (MPU) that
provides a system interface for users or service personnel who need to monitor or troubleshoot the
system.
For more information on configuring the maintenance port, refer to "Connecting to the MPU" on
page 4-2.
E. LEDs
The front panel of the SDU has two LEDs to indicate unit status:
• One green LED labeled Power
• One red LED labeled Fault.
Table 1-5 provides information about the LED signals.
F. Self-Test Button
The front panel of the SDU has a recessed button labelled Test.
NOTE: The Test button is recessed behind a red protective cap. To press the button, use a small
and thin tool with no sharp edges. You will not be able to press the button in far enough with
just your finger.
Table 1-5. SDU LED Status
Power LED Status Fault LED Status Description of SDU Status
LED is on LED is off No fault detected
LED is on LED is steadily on as long as
the fault exists
LRU fault detected
LED is on Flashing at 1 Hz with a 50%
duty cycle while the fault
exists
System fault detected but not isolated
to the LRU
Alternating flashing of Power and Fault LEDs Self-test in progress
DRAFT as of
4 Mar 2016