All
On behalf of the USAF, thanks for the advise. You'd think being in the military, we'd have some old field phones around and know how to do this, but everyone has gone radio and sat. We also thought about going to a surplus and buying some, but that just didn’t seam right, buying them back! Based on the posts, we've set up a test line with about 4k resistance and have tried everything from 9 volt battery to a 48 volt power supply. As one might assume, as the voltage goes up, so did our volume. I suspect it was more a function of the amount of current. It was the best at 48 volts. I found an article that indicated as long as you have 20mamp, you can communicate. We will have one chance to test on the real lines before we have to use this solution and any other thoughts you all have would be appreciated!
Thanks again,
Mark
