Yeah, I get it. I briefly had a 503 - fxs port for house line and fxo for the emergency (free) pots line from verizon (free because the triple play I signed up for is quite a bit less than the separate tv and internet i had before.) Anyway, I really liked the early dialing feature it had (so, for example, my asterisk dial plan could result in 411 or 7-digit dialing going more quickly without needing to wait N seconds.) Unfortunately, it was flaky, and at least once a month, the fxo port would just stop working - requiring a reboot. Given that the main thing I was using the fxo for was 911 (since even though I have voipo 911, the verizon one is more likely to work - not subject to the vagaries of the internet), this made it useless to me. It went to the junkpile.