Wayne,
Im guessing you are plugging the Call-A-Matic into the DB9 on the rear of the Mitel Cabinet this is fine butif your cable run to the Call-A-Matic is longer that 50Ft your asking for trouble as "Line Ground Noise" will eat up your RS232 circuit with a good power surge or lightning strike nearby. If your cable run is over really I dont recommend going over 20ft but I beleive EISA specs say 50ft. If your run is over that you need to look into putting in "Short Haul Modems" or you can use a "Mitel Dataset" or if you have a Super Console 1000 theres a data set port DB25 on the back of that & you can route the SMDR through that. Good Luck with it guy.