Checked the TXD line and it does not go to a plus voltage state. Tentec needs 0 to -15 for Mark and +2.5 to +15 for Space. Therefore Mark is good, but where does the Space get its needed plus voltage. Ed W3NR --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.467 / Virus Database: 266 - Release Date: 4/1/2003