The 20 wire cable that might have been an RS232 link is definitely not - among other signs, pin 3 is ground, not receive data. The S-100 interface card has no UART or intelligence, just routes the signal lines through an 8255A to the bus. Finally, opened the plotter itself - no microcontroller/processor, no logic circuits, just transistor drivers to activate the stepper motors and solenoids, wired to the various lines of the cable. So, yes, it is a parallel interface and it appears to be completely proprietary to the Strobe plotter. No fancy protocol to speak to it, at least, just raise lines to drive the motors one way or the other in 3.6 degree rotary steps. The power supply in the plotter has a 7805 on it, so appears to be standard TTL 5V interface at first glance. Seems it will be more straightforward than I thought to put this into service. Carl ________________________________ This e-mail message, including any attachments, is for the sole use of the person to whom it has been sent, and may contain information that is confidential or legally protected. If you are not the intended recipient or have received this message in error, you are not authorized to copy, distribute, or otherwise use this message or its attachments. Please notify the sender immediately by return e-mail and permanently delete this message and any attachments. Gartner makes no warranty that this e-mail is error or virus free.