Two points. First,there's the question 'are you trying to produce something that just _looks_ alike, or do you want something that's electrically compatible (i.e. can be swapped in in place of an original'? If the latter, it might be going to take a little work; it might not be just 'wire up some LEDs and go'. If you look at the indicator panel prints (pg. 190 of the RF11 prints), the incoming lines are tied to the base of a transistor; its emitter is tied to ground, and the light bulb is wired between the collector and +6.5V. This means, I think (I'm basicaly a software guy :-), that one turns the bulb on by putting a voltage on the input, which turns the transistor on, and current flows through the bulb to ground. (If I have that wrong, will someone please orrect me?) Given that the way TTL works is that 'logic' outputs actually sink currect when their output is '0' (i.e. current goes _in_ the 'output' pin), it might take a little work to make the right thing happen. Although maybe not; looking at the RK11-C prints, it seem to drive the indicator panel straight output is '1', the output's voltage floats high, and that's enough to turn on the transistor (above) driving the bulb. (Ditto the request for correction!) But the real issue with 'electrically compatible indicator panels' is the wiring. In the originals, the flat cables that drive them are soldered directly to the indicator panel board, and also to the paddle boards. So the _only_ standard interface location is the paddle boards. I suppose one could put Berg headers on both the indicator panel board and the paddle boards, and use a standard IDC cable betweenthe two... Mention of the paddle board interface brings me to the second point: even if one did produce electrically-compatible indicator panels - where are you going to use them in a PDP-11 system? Not in the CPUs - those all had their own front panels. The only PDP-11 devices which used indicator panels which I know of were: - the DX11 (I don't think anyone's got one of those) - the RF11 (ditto - although Guy was discussing emulating one at one point) - the RP11 (but the indicator panel is built into the controller rack there, so if one has an RP11, one already has the indicator panel) - the RK11-C (and several people who have those already have indicator panels) I agree, the indicator panels look cool - but where are you going to use one in a historical PDP-11 system? Sure, one could use either a electrically-compatible or non-electrically-compatible indicator panel anywhere you want, plugging into some non-historical hardware, but.. (The non-electrically-compatible indicator panel Dave did for the QSIC is initially being used in something which emulates an RK11 and/or RP11, so there's some rationale for it.) Noel