(3)
 The ACARS MU transmits the following messages to the FMGCs either automatically or manually:

 -Flight plan initialization
 -Wind message
 -Advisory message related to a "request not transmitted to the ground"
 -
Request for a pre-flight report

 -
Request for a post-flight report.

 (4)
 Each function is rendered operational or not depending on the message transmitted by the ACARS MU to the FMGCs.

 (5)
 The ACARS MU receives parameters from the FMGCs.

 D. Connection with the FWCs and SDACs
 (1) The ACARS MU provides the FWC1 and 2 with data indicating four ACARS configurations. The FWC1 and 2 enable display of the corresponding indications on the memo zone of the upper ECAM display unit. These indications are:
 -
ACARS MSG: indicates reception of a ground message

 -
ACARS STBY: indicates loss of communication with the ground

 -VHF3 : VOICE: indicates that the VHF3 transceiver is not controlled by the ACARS
R 1EFF : 001-049, 051-099, 101-105, 1 23-24-00Page 9 1 1 May 01/05 1 1 1CES 1 -ACARS CALL: indicates reception of a voice communication demand

 with the ground. The display unit only shows one indication even if several configurations are present at the same time. When the FWCs are no longer provided with this data by the ACARS MU, or do not receive it in normal conditions (incorrect refresh or validity), the ACARS MU appears on the faulty system list (ECAM STATUS page) and the amber ACARS FAULT warning appears on the upper ECAM display unit.
 (2)
 The ACARS MU receives the FWC1 main bus and can use any information present on this bus (available parameters are listed in the FWC interfaces ATA 31-52).

 (3)
 The ACARS MU receives the SDAC1 main bus and can use any information present on this bus (available parameters are listed in the SDAC interfaces ATA 31-54).

 E. Connection with the VHF3 Transceiver
 (1)
 The VHF3 has two audio type interfaces:

 (a)
 An audio input, an audio output and a transmission control discrete (push-to-talk) linked to the audio management unit (AMU) (Ref. ATA 23-51). This interface is used for voice communications.

 (b)
 An audio input, an audio output and a transmission control discrete (data keyline) linked to the ACARS MU. This interface is used for transmission and reception of the ACARS data.

 (2)
 The VHF3 can operate in two modes:

 (a)
 Radio mode: in this case, it activates its audio type interface with the AMU and de-activates its audio interface with the ACARS MU.

 (b)
 DATA mode: in this case, the process is reversed.

 (3)
 The ACARS MU controls the VHF3 operating mode through the voice/data select discrete:

 (a)
 When this discrete is a ground signal, the VHF3 operates in DATA mode.

 (b)
 When this discrete is in open circuit, the VHF3 operates in radio mode.

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 (4)
 The VHF3 has two frequency control interfaces:

 (a)
 A digital input linked to the ACARS MU (input A)

 (b)
 A digital input linked to the RMPs (input B).

 (5)
 The ACARS MU applies a command signal to the VHF3 to take into account its frequency inputs through the port select discrete.

 (a)
 When this discrete is a ground signal, the VHF3 takes into account input A and operates on the frequency transmitted by the ACARS MU.

 (b)
 When this discrete is in open circuit, the VHF3 takes into account input B and operates on the frequency transmitted by the RMPs.

 (6)
 Three cases may arise:

 (a)
 The VHF3 operates in DATA mode. In this case the VHF3 frequency is controlled through the ACARS MU. The voice/data select and the port select discretes are grounded by the ACARS MU.

 (b)
 The VHF3 operates in radio mode and its frequency is controlled through the RMPs. The voice/data select and the port select discretes are in open circuit.

 (c)
 The VHF3 operates in radio mode and its frequency is controlled through the ACARS MU. The voice/data select discrete is in open circuit and the port select discrete is grounded. In this case, the frequency transmitted by the ACARS MU is a frequency entered by the crew (on one MCDU) or a frequency received in a ground message.

 NOTE : When the ACARS MU is not supplied or if it is faulty, the
　
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