implementation                 //  important    fichier     rscom.dll      dans ton folder 
{$R *.DFM}                     //         de:Yann   site://www.delphipage.net/  (zip 39k)
// inport externe in rscom.dll
function OPENCOM(OpenString:PChar):Integer; stdcall; external 'RSCOM.DLL';
procedure CLOSECOM(); stdcall; external 'RSCOM.DLL';
procedure TXD(d:WORD); stdcall; external 'RSCOM.DLL';
procedure DTR(d:WORD); stdcall; external 'RSCOM.DLL';
procedure RTS(d:WORD); stdcall; external 'RSCOM.DLL';
 
procedure TForm1.FormCreate(Sender: TObject);
begin
OpenCom('COM1: baud=9600 parity=N data=8 stop=0');     // open le port
..... 
....
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
 CloseCOM;   // close le port serie
.....
end;

procedure TForm1.BtnClick(Sender: TObject);   //  bouton  allume
begin
  TXD(1);  // line pin 3 on          TXD( 0 ) =off
  DTR(1);  //         pin 4
  RTS(1);  //          pin 7         
  ....                         
                        voici quelques lines importantes      et  merci a  Yann.
Fred