I found that manual online, but I still wasn't sure. They use "Input 1" and "Input 2". They don't use the words "Hi" and "Lo" though.

If I were to just make an educated guess, then I think Lo is the one to use like you mentioned. Just because it is on the bottom and I assume it is "2".

Found a picture online of what it looks like. You can see the inputs on the left. Hi is on top and Lo is on bottom.

http://www.flickr.com/photos/51436564@N03/4834824474/in/photostream/