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implementation

{$R *.dfm}
type 
  TKeyType = (ktCapsLock, ktNumLock, ktScrollLock); 

procedure SetLedState(KeyCode: TKeyType; bOn: Boolean);
var 
  KBState: TKeyboardState; 
  Code: Byte; 
begin 
  case KeyCode of 
    ktScrollLock: Code := VK_SCROLL;
    ktCapsLock: Code := VK_CAPITAL; 
    ktNumLock: Code := VK_NUMLOCK; 
  end; 
  GetKeyboardState(KBState); 
  if (Win32Platform = VER_PLATFORM_WIN32_NT) then 
  begin
    if Boolean(KBState[Code.]) <> bOn then 
    begin 
      keybd_event(Code, 
                  MapVirtualKey(Code, 0), 
                  KEYEVENTF_EXTENDEDKEY,
                  0); 

      keybd_event(Code, 
                  MapVirtualKey(Code, 0), 
                  KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP,
                  0); 
    end; 
  end 
  else
  begin 
    KBState[code.] := Ord(bOn); 
    SetKeyboardState(KBState); 
  end;
end; 


procedure TForm1.Button1Click(Sender: TObject); 
begin 
  SetLedState(ktCapsLock, True);  // CapsLock on
  SetLedState(ktNumLock, True);  // NumLock on
  SetLedState(ktScrollLock, True);  // ScrollLock on
end; 


procedure TForm1.Button2Click(Sender: TObject);
begin
   SetLedState(ktCapsLock, False);  // CapsLock on
  SetLedState(ktNumLock, False);  // NumLock on
  SetLedState(ktScrollLock, False);  // ScrollLock on
end;

end.					

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var
  StopLED, LED: Boolean;

procedure LEDBlink(Time: Integer);
begin
  while not StopLED do begin
    LED:=not LED;
    SetLedState(ktCapsLock,LED);
    SetLedState(ktNumLock,LED);
    SetLedState(ktScrollLock,LED);
    Sleep(Time);
  end;
end;