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unit uSubObject;

interface

type

{ TAmplifierÓëTTuner£¬TCDPlayer£¬TDVDPlayerÏ໥ÒÀÀµ¡£ }
{ ÔÚTTunerµÈµÄ¼òµ¥ÊµÏÖʱÓò»µ½¶ÔTAmplifierµÄÒýÓ㬠}
{ µ«ÏÖʵÉú»îÖоÍÓ¦¸ÃÈÃTAmplifierÌṩ·þÎñ£¬ËùÒÔÕâÀï±£ÁôÁË¡£ }
{ TProjector¶ÔTDVDPlayerµÄÒýÓÃÒ²ÊÇͬÑùµÀÀí¡£ }
{ Ç°ÖÃTAmplifierÒ²¿ÉÒÔ£¬°ÑTAmplifierµÄÉùÃ÷·ÅÔÚTTunerµÈÉùÃ÷µÄºóÃæ }

TTuner = class;
TCDPlayer = class;
TDVDPlayer = class;

TAmplifier = class(TObject)
private
FTuner: TTuner;
FCD : TCDPlayer;
FDVD: TDVDPlayer;
FDescription: String;
public
constructor Create(aDescription: String);
procedure Open;
procedure Off;
procedure SetStereoSound;
procedure SetSurroundSound;
procedure SetVolume(aLevel: Integer);
procedure SetTuner (aTuner: TTuner);
procedure SetCD (aCD : TCDPlayer);
procedure SetDVD(aDVD: TDVDPlayer);
function ToString: String;
end;

TTuner = class(TObject)
private
FAmplifier: TAmplifier;
FDescription: String;
FFrequency: Double;
public
constructor Create(aDescription: String; aAmplifier: TAmplifier);
procedure Open;
procedure Off;
procedure SetAm;
procedure SetFm;
procedure SetFrequency(aFrequency: Double);
function ToString: String;
end;

TCDPlayer = class(TObject)
private
FAmplifier: TAmplifier;
FDescription: String;
FCurrentTrack: Integer;
FTitle: String;
public
constructor Create(aDescription: String; aAmplifier: TAmplifier);
procedure Open;
procedure Off;
procedure Eject;
procedure Play(aTitle: String ); overload;
procedure Play(aTrack: Integer); overload;
procedure Stop;
procedure Pause;
function ToString: String;
end;

TDVDPlayer = class(TObject)
private
FAmplifier: TAmplifier;
FDescription: