(3)
CAA recording The principle of CAA recording requires (in addition to the FAA recording principle) that the noises picked up by the boomset microphones be recorded even when these microphones are not active
i.e. when the push-to-talk switches on the side-sticks or on the ACPs are not activated. This in order to reinforce the sounds picked-up by the area microphone. This configuration is named "hot-mike". A shunt is installed on the pin-programming terminal of the AMU to activate the CAA recording (Ref. Para. Operation - Pin Program).
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(4) DFDR/CVR Synchronization
The two recorders (CVR and DFDR) are synchronized:
-The DFDR receives the GMT signal from the FDIU,
-Also, the CVR receives the GMT signal from the FDIU. This signal is sent to the CVR via the AMU where it is mixed with the 3rd occupant audio signals.
R **ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
(5) Operation (Ref. Fig. 029) Following the AMU pin-program modification, the SELCAL-CALL card generates an information message. This message is sent to the different audio cards and therefore to the various channels of the logic processing function. This information is taken into account, then the logic processing channel sets the CAA certification module into service. The LF signals are picked-up by the boomset or oxygen mask microphone (when in use) at the output of the 0db gain amplifier. They are sent to the CAA Certification Module and, from there, to the CVR output.
E. Flight Interphone Function
(Ref. Fig. 030)
(1)
General
The flight interphone enables:
-
Telephone conversations between the various stations in the cockpit
-
Telephone conversations between the cockpit and the ground crew via the external power panel.
(2)
Composition of the circuit The flight interphone circuit comprises a summing amplifier equipped with:
-7 microphone inputs
input impedance : 150 ohms
input level : 0.250 V.
-3 audio outputs impedance : 600 ohms - Power 35 mW plus or minus 5 mW for ground crew reception output impedance : 600 ohms - Power 10 mW for AMU external reception, output 6 internal output impedance : 2.2 kohms for AMU internal reception relevant to the various cards.
This circuit also comprises :
-
1 power supply for microphones of channels 6 and 7.
-
1 interface and current detection circuit for channel 6.
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CAA Certification - Block Diagram
Figure 029
R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 79 1201-220, 1May 01/05 1 1 1CES 1
Flight Interphone - Block Diagram
Figure 030
R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 80 1201-220, 1May 01/05 1 1 1CES 1 -1 cut-off circuit for channel 7.
(3) Operation The input signal from the various microphones used in the aircraft (hand microphone, boomset, mask microphone) is applied to inputs 1 to
7. A specific power supply circuit is provided for the microphones of inputs 6 and 7 (they have no transmission card to supply them). A current detection circuit on channel 6 and a cut-off relay on channel 7 insulates the channels when they are not used. The L/G relay controls this cut-off relay. The amplified LF output signal is then available on the 3 windings of the secondary of the output transformer:
-
600 ohm output for ground crew.
-
600 ohm output for audio output No. 6.
-2.2 Kohm output for the various AMU audio cards.
R **ON A/C 106-149, 221-299, 301-399, 401-499,
E. Flight Interphone Function
(Ref. Fig. 030A)
(1)
General
The flight interphone enables:
-
Telephone conversations between the various stations in the cockpit
-
Telephone conversations between the cockpit and the ground crew via the external power panel.
(2)
Operation The flight interphone comprises the following functions:
-microphone inputs
-amplification and summation
-audio output.
(a)
Microphone inputs There are two types of microphone inputs:
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