one thing i've done along the same lines if to have the hot d call my set.. usually 6 to 10 at a time. or put a ringer in series with the jumper and call it.. if that rings there is a ringer on the far end.. you can also take a reading with an analog meter on the cable pair, jumper removed, then take the same reading reversed, watch the needle swing, that "kick" in the swing of the needle will be a cap on the far end... it's a old trick but for a few analog tn's you need back, i've done it..
john poole
bellsouth business
columbia,sc