many thanks majenko
if it proves to be as you suspect do you know of a hardware solution any recomendations
Yes, as I think I mentioned - a MAX232 chip or similar. There are literally millions of articles on the 'net about using them on the Arduino.
The MAX232 is an RS-232 driver chip that includes a charge-pump system to convert 0-5V into +10v and -10v respectively. It usually has 4 channels, but you'll only need one or two. All it takes is 4 capacitors. There are many suppliers of pre-made boards, marketed as "TTL to RS-232" or similar.