Overview
An airborne telephone system provides analog and digital communications between the aircraft and terrestrial telephone and data networks. The system connects to these networks through the Iridium constellation of low-Earth orbit satellites. The primary system component is a cabin telecom router that provides routing and control functions from the cabin handsets to the various passenger communications systems on the aircraft.
The system provides low-cost satellite-based voice and data communication functions including voice communication, fax communication, and Airshow network update. Iridium requires a subscription through a service provider, such as Satcom Direct.
Iridium Communication System (ICS) Transceiver
The ICS-100 Iridium Communications System incorporates a single channel Iridium transceiver providing a standalone, comprehensive communication system. The ICS-100 permits connections of conventional telephony devices or legacy CTU systems via either standard 2-wire 'Tip & Ring' circuits or 4-wire audio connections. Standard CTU features include: intercom calling, call transfer, conferencing, and follow on dialing.
The system provides voice service and data communications up to 24000 Bps via serial port connection.
Iridium Communication System (ICS)
The ICS provides either one or two satellite communication channels. Voice communication is through the cabin telephone unit using the cabin headsets. If so configured, the ICS can also handle fax communication. Alternately, fax communication is handled through the SATCOM system.
Through an RS-232 serial data bus, the ICS is used to update the airshow network.
The Iridium satellite network consists of 66 satellites in a low earth orbit providing global coverage. If the aircraft is not equipped for SwiftBroadband (SBB), the default voice communication system is the Iridium system. If SBB is installed, then the low-cost channel offered through the SATCOM system becomes the default system.
Iridium communication can be interrupted when the Iridium and SATCOM systems are operating simultaneously. This occurs when the Iridium antenna is between the SATCOM antenna and the SATCOM satellite. The more powerful SATCOM signal overpowers the Iridium signal, interrupting operation.
When the situation is corrected, communication returns to normal.
The ICS is always on when AC power is available to the aircraft. However, communication is not possible unless the antenna has clear access to the satellites. The availability of Iridium is indicated on TSEs that have a Cabin content category via the Networks icon.
If desired, to ensure uninterrupted communication over Iridium, including uninterrupted airshow network updates caused by antenna interference, the SATCOM system may be temporarily suspended. Selecting the Suspend Satcom button will terminate SATCOM transmission.
The SATCOM system can be re-enabled, however a caution message will be displayed indicating that future Iridium communication may be interrupted.
System Interface
The ICS 100/200 comm unit is powered from DC Bus 1 through SPDA 4. The access to the CB is via the electrical management system (EMS) CDU.
Communication between the ICS and CES is via a Data Terminal Equipment (DTE) communication protocol with MCE 1. This includes an RS-232 link for the update of the airshow network.
A discrete fail signal will be sent from the cabin telephone unit if it detects that there is no communication over the ICS channels.
The ICS-100 unit has a single voice channel with the Cabin Telephone Unit (CTU). The ICS-200 unit has two channels. Voice communication signals from a handset are routed to the CTU. The CTU selects the default channel for communication with the ICS. The signals are then sent through the antenna to the Iridium satellite network.
