I'll leave it up to Steve to answer that, but this may help you get the idea:

https://sites.google.com/site/steveyegge2/five-essential-pho...

This is a Steve's post on how he conducts and what he expects from phone interviews.

It's over seven years old so proceed with care -- it's possible that his views changed since then.

Also, this is probably more of a bare minimum rather than the whole picture.