var
hCommFile: THandle;
procedure TForm1.Button1Click(Sender: TObject);
var
PhoneNumber: string;
CommPort: string;
NumberWritten: LongInt;
begin
PhoneNumber := "ATDT 1-555-555-1212" + #13 + #10;
CommPort := "COM2";
{Open the comm port}
hCommFile := CreateFile(PChar(CommPort), GENERIC_WRITE, 0, nil,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if hCommFile=INVALID_HANDLE_VALUE then
begin
ShowMessage("Unable to open "+ CommPort);
exit;
end;
NumberWritten:=0;
if WriteFile(hCommFile, PChar(PhoneNumber)^, Length(PhoneNumber),
NumberWritten, nil) = false then
ShowMessage("Unable to write to " + CommPort);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
{Close the port}
CloseHandle(hCommFile);
end;
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