Audio Circuit - Block Diagram
Figure 022
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(3) Reception function (Ref. Fig. 022A) The audio signals from the various communication and navigation units are first connected to analog/digital converters, and then to the DSP located on the audio boards. Dedicated inputs exist on the DSP for filtered signal (ADF and VOR). The DSP is also connected to a control module which provides information computed from the ACP (potentiometers position, Voice filter selection) and from the FCU (DME coupling to VOR or LS). After digital processing inside the DSP, the resultant signal is converted into analog and sent to the output transformer.
NOTE : A minimum VHF and HF reception level is ensured when the
____ potentiometers on the ACP are set to minimum. The minimum reception level is deleted when the potentiometers are set to OFF. Minimum reception level is -32 dB with reference to maximum level.
**ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
(4) VOR/DME/ILS/MLS switching
(Ref. Fig. 023)
(a)
Purpose In normal configuration, the DME reception is coupled with the VOR reception. However, in certain ILS or MLS approach conditions, the DME used must be aurally identified. The DME reception must therefore be coupled with the ILS or MLS reception.
(b)
Operation The ND (Navigation Display) mode selector switch or the ILS pushbutton switch is used for switching control (REF ATA 31 - DMC circuit (WT)). Action on one of these commands sends a ground to the switching relays which connect the DME receptions to the ILS or MLS receptions.
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Audio Management Unit - Simplified Schematic of Reception Circuit
Figure 022A
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VOR/DME/ILS/MLS Switching - Block Diagram
Figure 023
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(4) DME/VOR/LS switching
(a)
Function In normal configuration, the DME reception is coupled with the VOR reception. However, in certain landing system approach conditions, the DME used must be aurally identified. The DME reception must therefore be coupled with the MMR reception.
(b)
Operation The LS pushbutton switch is used for switching control (Ref. ATA 31 - DMC circuit (WT)). Action on this command sends a ground to the AMU which couples the DME receptions to the MMR receptions.
**ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
(5) VOICE/ON function
(Ref. Fig. 024)
(a)
Reason 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/ON 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 receive a 1020 Hz frequency-modulated signal and at the same time transmit this signal at 1000 Hz to the audio system. The 1000 Hz signal is generated by their synthetizer (the aeronautical standards specify that the ADF ground stations must be modulated at a frequency of 1020 Hz plus or minor 50Hz).
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Navigation Reception Mode - Block Diagram
Figure 024
R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 66 1201-220, 1May 01/05 1 1 1CES 1 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 attenuater filter for the reception bands of the ADF and VOR systems. This filter attenuates the 1000, 1020 and 1350 Hz frequencies by more than 32 dB. A compensation amplifier is provided to compensate for the insertion losses of this filter. Action on the VOICE pushbutton switch located on each ACP switches the attenuation filter into or out of service. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM Communications 通讯2(117)
