Hi Jim - thanks for your help. I googled Kalatel also and wasn't able to find any manuals on the exact model. I am buying two Digimerge DHU516251's and they have a two-wire 485. The user can work the Kalatel with either DVR, but it would be nice to be able to use the built in PTZ features in the Digimerge. The DBR supports a variety of protocols, including Pelco-D, Everfocus, Pelco-P etc.