I have this Kensington Expert Mouse here (c. 1995), and I'm wondering if I'm missing an external adapter box... it has a Mac-style DIN-8 for a connector, and inside, I see 3 chips - an LM358 near the DIN-8, an LP339N (quad comparator?) and a 24-pin Motorola SC417907P with an adjacent 4.00MHz crystal resonator, clearly some sort of microcontroller being used as a mouse protocol encoder. One mysterious part is the optical receiver, an SD6150... it's an acrylic-housed device with a visible silicon die, and 5 leads. It's positioned to catch the light off of the marked roller that catches light from an IR diode, so it's got to be something like a multiple-element photodiode (they are marked "DTC1" and "DTC2"), but googling isn't not revealing any hard details on the part. I _think_ I can see 4 "panels" on the die, so it might be a Common lead and 4 light sensitive patches that the board would use to turn a strobed light from the roller into both phases of the quadrature waveform. I don't think the folks that once used this had old Macs (perhaps they did 10 years ago), so my first thought is... what protocol might this speak and am I missing an external adapter to, say, a PS/2-style mouse cable? Another possibility I can think of is that it is designed to hook to a Microsoft Bus Mouse board (probably have one of those hanging around here somewhere). I did some googling on it and can't find any internals info or any "hack" articles. Honestly, I could use this even if I have to extract raw quadrature and do something with that. It's a single-sided board, so reverse-engineering it is not impossible, but I thought I'd ask first and see if anyone knows some technical details on it. Thanks, -ethan