(c)
 Released position: VOICE/ON legend off The filter is not used, the operator simultaneously receives the marker identification and the voice transmission.

 (d)
 Pressed in position: VOICE/ON legend on A command from the CPU sets the filter into service. The 1000 -1020 - 1350 Hz frequencies are greatly attenuated. Only the voice transmissions are audible.

 NOTE : The audio outputs of the communication channel and the
____ ILS, MLS, MKR navigation do not transit via the filtering module.
 C. Emergency Function (Ref. Fig. 025, 026)
 (1)
 Purpose The emergency function is used in case of loss of communications on the Captain or the First Officer channels. This function switches the Captain or First Officer communications to the 3rd Occupant station. In this case, the Captain (or the First Officer) uses the ACP located on the overhead panel to make his microphone or audio selections.

 (2)
 Operation The AUDIO SWITCHING selector-switch 16RN located on the overhead panel is used to switch to emergency configuration. Turning this switch, sends a ground to the Captain (or First Officer) and 3rd Occupant switching relays. The various microphone inputs, commands and audio outputs are connected to the microphone inputs, commands and audio outputs of the 3rd Occupant. This switchover is indicated on the upper ECAM display unit (REF ATA 31-54-SDAC).

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 Microphone Switching - Block Diagram
 Figure 025

R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 68 1201-220, 1May 01/05 1 1 1CES 1

 Audio Switching - Block Diagram
 Figure 026

R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 69 1201-220, 1May 01/05 1 1 1CES 1 NOTE : When the emergency function is activated, the various audio

____ inputs and outputs at the 3rd Occupant station are no longer connected to their circuit. Therefore, the 3rd Occupant cannot use his audio integrating circuits.
 (3) Not Applicable

R **ON A/C 106-149, 221-299, 301-399, 401-499,
 (5) VOICE/ON function
 (a)
 Function The VOR, ADF navigation ground stations transmit a morse code which is used to identify them. However, certain stations, in addition to their code, transmit recorded voice information. This information informs the crew of subjects such as: latest weather information, state or special information concerning terrains etc. (e.g.: ATIS station). In order not to hinder the reception of this information, the VOICE/IDENT function greatly reduces the morse code reception. It is attenuated until it becomes practically inaudible while this information is being transmitted.

 (b)
 Operation The transmission modulation frequency for ground station codes is 1020 Hz. However, certain onboard equipment (COLLINS ADF) receive a 1020 Hz frequency-modulated signal and at same time transmit this signal at 1000 Hz to the audio system. The 1000 Hz signal is generated by their synthesizer (the aeronautical standards specify that the ADF ground stations must be modulated at a frequency of 1020 Hz plus or minus 50 Hz). Furthermore, the DME reception is coupled to the VOR reception (in normal operation). Thus the DME marker identification-code is transmitted with a frequency modulation of 1350 Hz. The filtering circuit of the navigation channels therefore comprises an attenuation filter for the reception bands of the ADF and VOR systems. This digital filter attenuates the 1000 and 1020 Hz frequencies by more than 32 dB. Action on the VOICE pushbutton switch located on each ACP has the following effects:

 -Released position, VOICE/ON off The filters are not used, the operator simultaneously receives the marker identification and the voice transmission.
 -Pressed in position, VOICE/ON on
 1EFF : ALL 1 23-51-00Page 70 1 1 Aug 01/05 1 1 1CES 1 The DSP directly processes the filtered signals. The 1000 -1020 Hz frequencies are greatly attenuated, the DME identified is cut off (1350 Hz). Only the voice transmissions are audible.

 NOTE : The audio outputs of the communication channel and the
____ MMR, MKR navigation do not transit via digital filters.
 C. Emergency Function (Ref. Fig. 026A)
 (1)
 Purpose The emergency function is used in case of loss of communications on the Captain or the First Officer channels. This function switches the Captain or First Officer communications to the 3rd Occupant station. In this case, the Captain (or the First Officer) uses the ACP located on the overhead panel to make his microphone or audio selections. The AUDIO SWITCHING selector-switch 16RN located on the overhead panel is used to switch to emergency configuration. This switchover is indicated on the upper ECAM display unit (REF ATA 31-54-SDAC).
　
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