DIY interface...technical questions

[hwg]

Hi,
I'm quite keen on making my own interface for the ElanScan software, but I'm struggling to find any specs on the internet! so lets start with some simple questions.
is the ALDL port on the elan a 5V or 12V plug?
does it pull up the dataline, or is the interface expected to do that*?
the ALDL standard appears to be inverted from normal 232, does the signal get inverted in the elan-scan software, or is it in the interface?

Thanks, harry

*alternatively, how does the half duplex arrangement work?