Route one instrument to two output sources - you can select between either output source or use both at the same time. The ABY Pro features isolated channels so there's no crosstalk or bleed-through. It uses Ebtech customer isolation transformers to prevent ground loops, and includes silent switching (so there are no pops when switching), plus polarity reverse and ground lift switches. Other features include LED indication, cold rolled steel housing, powers from 9V battery or adapter.