User's Guide

DRAFT
Page 1-3
17 Mar 2016
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SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
ARINC 781-500 SDU and SCM
© Honeywell International Inc. Do not copy without express permission of Honeywell.
The A781-500 system consists of the Satellite Data Unit (SDU) and the Satellite Data Unit Configuration
Module (SCM).
Figure 1-2 illustrates the A781-500 system.
a2
Figure 1-2. A781-500 Avionics System
A. SDU
The SDU is the central communications processing and control unit and largely determines the
functionality of the complete SATCOM system. It manages interfaces, routing and priorities, and call
channel establishment and tear down. SDU provides RF power amplification using an internal high
power amplifier.
The SDU is divided into several shop replaceable units that are electrically connected via the
backplane. Various SRUs are also connected using RF cables.
B. SCM
The SCM is an external peripheral of the SDU and provides a dedicated interface to the SDU. It
stores Secure and User ORTs. The SCM can accommodate up to four Universal Subscriber Identity
Modules (USIM) that store subscriber information for the SBB network.
By storing configuration information independent of the SDU, the SCM facilitates efficient SDU
replacement. A new SDU that replaces a faulty SDU does not require any configuration. All
configuration information is obtained from the SCM.
DRAFT as of
4 Mar 2016