Hey, how you doing.. I was doing a search for TM990 for work and came across your message. I work on that antique stuff you have come across. TI had two calculator type programmers. These units were used with the 5TI sequencers and PM550 PLC's. This stuff is still being used in industry for controlling machines. I've had to refurbish a couple of the larger calculator type programmers last year. They are a polled RS232 device that only talks when told to by the PLC / Sequencer. http://www.datamath.org/ This is where i got the pictures... There is some thrill rebuilding these things hooking them up and punching in some ladder logic and watching the flashing lights on the I/O racks.. Some of the stuff you pick up may still bring a decent price on ebay.. Even this old seemingly antique stuff.. Just my .02 Duane Hofstetter ke8bg(a)triad.rr.com duaneh(a)delta-control.com http://www.delta-control.com