Oh, so I just found this with Google:
"XR-5 has foldback/monitor and MIDI synchronizing features previously unavailable in this price range. (For those of you unfamiliar with the term "foldback" it is the English equivalent of what American musicians typically call "monitor".) The Alternate mix mode lets you independently select the signal from the input jack or the tape playback. Prefader effect send, inline monitor and other functions are possible using this function. Post foldback/monitor send function routes the foldback/monitor signal to the Aux Send. You can actually mixdown at the same time you add reverb to a tape when foldback/monitor is activated. "
and
"There are some other neat features, too. A foldback/monitor output terminal is set so you can use the prefader effect delivery and monitoring. The mixer's output level (L,R,Aux1, Aux 2) and tape (tracks 1, 2, 3, 4) can be displayed on a switchable meter. There's also a headphone terminal for direct input to your brain, and a display that tells you where you are at a glance. "
