721 compatability
I have a 721/510 connected to DPP Twin and Separator on 721 and it works. However, I hate the 721. I only keep it because of no DVR fee and I don't keep a LAN line so it saves me $11 a month, but I'm tempted to pay the diff. and upgrade, because they are not upgrading the 721 to name based recording and everytime I have to do a front panel reset it takes up to 15 minutes to get back to programming. Very frustrating. I would go with the 625 or 522 if it was me.