Barry, didn't you ask (under the pseudonym of Fred Feuerstein) for a description of the switches on a DS120 Terminal Controller? I managed to find a user manual from the stone age, stating that the "Logic Card" is part number 512000-2. Not quite the 5120000-1 that you mention in your posting, but possibly close enough to provide hints for what functions might be there. YMMV... This is what the manual says about the DIP switches: SWITCH FUNCTION 1 Carriage motor disable (test only) * 2 Reverse channel override * 3 FDX/HDX override * 4 Local Auto-LF override ** 5 Parity odd (ON) parity even (ON) ** 6 Parity enable (ON) parity disable (OFF) 7 AUTO-LF from line (ON) disable (OFF) ** 8 X-on, X-off handshaking enable (ON) disable (OFF) * On DECwriter models with the 8-key control pad, these switches are duplicated on the keyboard. Those models with the 3 rocker-switch panel must control these features with the DIP-switches. ** See Appendix B, "Additional User Information", for a functional description of these switches. End of cite. Appendix B talks a lot about half-duplex modes, which I presume will not be used with your PDP-11. Hence, you will want to have switches 2 & 3 in the OFF position. The description of switch 5 obviously contains an error. For even parity, the switch needs to be in the OFF position (says appendix B). Another noteworthy cite: "If parity is disabled by DIPswitch #6 "OFF", then DIPswitch #5 provides 8th bit spacing when "ON" and 8th bit marking when "OFF"." In other words, you actually cannot select "no parity", but you can set "mark" or "space" parity. You report having trouble with the 20mA interface. Maybe you need to switch from active to passive or vice versa? - Here's what the manual has about it: 3.1.3 20 MA CURRENT LOOP A 20mA current loop interface is provided featuring a photo isolated receiver and transmitter. The receiver and transmitter may be configured to operate in either passive or active mode. Unless otherwise specified at the time of purchase, the DS120 comes configured with a passive transmitter and receiver. Although specified at 20 mA, the signal line currents flowing in the receiver loop may be as high as 80 mA without harming the interface. Any current in excess of 15 mA will be interpreted as a mark, and any current under 3 mA is interpreted as a space. 1500 volts of isolation is provided by the photo isolater if passive is employed. The jumper configuration for the current loop interface is as follows: W1 W2 W3 W4 W5 W6 W7 W8 W13 W14 ------------------------------------------------------------------- PASSIVE Out In In In In Out Out Out Out Out ACTIVE In Out Out Out Out In In In In In The connections for this interface are as follows: PIN 2: Transmit - 3: Receive - 5: Transmit + 7: Receive + End of cite. Hope this helps. If you need more information, I can get whatever is printed in the manual for you. I do have a LA36, but it features the original DEC controller board, so I have no way of actually trying anything. -- Andreas Freiherr Vishay Semiconductor GmbH, Heilbronn, Germany http://www.vishay.com