Documation - Apple I/O

Just to take the "opto / no opto" discussion public.. in respect of connecting the Documation TTL outputs to the TTL inputs of an Apple VIA card in an Apple ][ ... I respectfully beg to disagree with my Learned Friend Dr. Duell. As I privately wrote to Sellam, I am afraid of (and have been badly bitten by) directly interfacing dissimilar machines, and then encountering poorly-designed power supplies that 'hunt' and attempt to regulate each other over the logic lines, with occasionally spectacular results. Wiring up a couple of octal or hex optoisolators should take a two hours max, and then no worries, Moit! I am just trying to err on the side of caution. Were it me, with my resources and equipment, I'd just measure between the devices to make sure no VooDoo was lying in wait, then go ahead and splice the cables. In Sellam's case, he does not have rooms full of sophisticated test gear, and so I thought isolating the signals would serve to protect the machines, especially the card reader I/O circuits. Your Milage May Vary, as they say. Cheers John