Winetech :
I agree with phonemeister that a PDKU would be the easiest solution, however, if you need to... I would install the 24V unit at the phone system side and connect the power leads to the next pair of wires open going to the door phone. Is the wiring a home run to the system, or is it spliced on other cable pairs?

Ottersnose :
The second pair on circuits 1 ~ 8 of a BWDKU card are not used. They will not supply power to a DDCB. To install a DDCB connected to a BWDKU card an external power source is required. This would usually be a 120 VAC to 24 VDC converter


- Tony
Ohio Data LLC
Phone systems, data networks, firewalls and servers in Central Ohio.
Some people aren't used to an environment where excellence is expected.