**ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
 (2) SELCAL
 (a) Ground system (Ref. Fig. 032) The ground system transmits, via VHF or HF transmitters, a selective call code. This code comprises 2 consecutive pulses each containing a mixture of the 2 frequencies. This enables the calls to be differentiated. The call comprises a single-code transmission without repeat.

R **ON A/C 106-149, 221-299, 301-399, 401-499,
 (2) SELCAL
 (a)
 Ground system (Ref. Fig. 032) The ground system transmits, via VHF or HF transmitters, a selective call code. This code comprises 2 consecutive pulses each containing a mixture of the 2 frequencies. According to the ARINC 714 specification, this enables the calls to be differentiated. The call comprises a single-code transmission without repeat.

 (b)
 Aircraft system

 **ON A/C ALL
 **ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
 (Ref. Fig. 033)
R **ON A/C 106-149, 221-299, 301-399, 401-499,
 (Ref. Fig. 033A)
 1EFF : ALL 1 23-51-00Page 86 1 1 Aug 01/05 1 1 1CES 1

R  SELCAL System - Ground System Figure 032
 1EFF : 1 1 1CES  ALL  1 111 23-51-00 Page 87 Feb 01/04

 SELCAL System - Aircraft System
 Figure 033

R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 23-51-00Page 88 1201-220, 1May 01/05 1 1 1CES 1

 SELCAL System - Aircraft System
 Figure 033A

R 1EFF : 106-149, 221-299, 301-399, 401-499, 1 23-51-00Page 89 1 1 Aug 01/05 1 1 1CES 1 **ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,

 The aircraft receivers detect and capture the call signals transmitted by the ground stations (VHF or HF). Once detected, the signals are sent to the AMU SELCAL card. This SELCAL card is equipped with 5 inputs. These inputs correspond to the various communication facilities on the aircraft (VHF1 - VHF2 - VHF3 - HF1 - HF2 in accordance with aircraft definition). The SELCAL decoder permanently scans the 5 inputs on which the calls may be present. It analyzes the received signals to check if they comprise the frequencies relevant to aircraft code. The operator programs this code on the SELCAL code panel. If the frequencies and aircraft code correspond, the warning system transmits an aural signal. The CALL legend on each ACP associated to the system which received the call (VHF1 - VHF2 -VHF3 - HF1 - HF2) comes on. Push the RESET pushbutton switch located on each ACP to reset the aural and lighted call.

R **ON A/C 106-149, 221-299, 301-399, 401-499,
 The aircraft receivers detect and capture the call signals transmitted by the ground stations (VHF or HF). Once detected, the signals are sent to the AMU SELCAL board. This SELCAL card is equipped with 5 inputs. These inputs correspond to the various communication facilities on the aircraft (VHF1 - VHF2 - VHF3 - HF1 - HF2 in accordance with aircraft definition). The SELCAL function continuously monitors the digital data of the five radio communication channels. It analyzes the received signals to check if they comprise the frequencies relevant to aircraft code. The operator programs this code on the SELCAL code panel. If the frequencies and aircraft code correspond, the warning system transmits an aural signal. The CALL legend on each ACP associated to the system which received the call (VHF1 - VHF2 -VHF3 - HF1 - HF2) comes on. Push the RESET pushbutton switch located on each ACP to reset the aural and lighted call.
 1EFF : ALL 1 23-51-00Page 90 1 1 Aug 01/05 1 1 1CES 1 **ON A/C ALL

 (c)
 Associated peripheral assemblies
 The SELCAL system is associated with:

 -
The radio communication systems VHF1 - VHF2 - VHF3 - HF1 - HF2 (in accordance with aircraft definition).

 -
The Flight Warning Computer (FWC) system.

 (d)
 Operation of the system

R **ON A/C 001-049, 051-099, 101-105, 151-199, 201-220,
 (Ref. Fig. 034)
 1 Operation
_ The SELCAL signal issued by the various communication assemblies is applied, depending on its source, to one of the 5 input channels (VHF1, VHF2, VHF3, HF1, HF2). An input compressor-filter first processes this signal:
 -
The input compressor (comprises a high gain amplifier and a deviation detector amplifier) delivers an LF signal with constant amplitude irrespective of input signal level

 -
The filter eliminates all frequencies above 3 Khz to enable

 further processing of the signals by digital filtering. At output of the 5 filters, the signals are sent to an analog-digital converter. This converter has 2 functions:
 -
It constantly scans the 5 analog inputs under the control of the calculating unit.
　
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