I have a Melco M-628 Power supply I got in a big box of phone stuff. Anybody have any idea what it does and was used for?? I have seen just about every phone instrument, tester, and equipment made, but this one is stumping me. It has 2 4-wire mod jacks on the front, and a 4-wire screw terminal strip labled "grn red blk yel". It uses 2 22.5v batteries (which I don't have) and also has a LED to indicate "T & R shorted"