The new KNX-powersupply from Mean Well has two outputs: one with KNX choke output and an additional output for ancillary power.
Each KNX-device uses 10 mA from the powersupply during sending and receiving signals on the bus.
The choke output is 640 mA which means that you can connect a total of 64 KNX-devices to the same output.
The second output is an “extra” 30 VDC 640 mA-output. It is used if any device requires external powersupply,
or to supply one additional KNX-line together with an external KNX-choke. The powersupply unit has a LED-indication
in the panel that indicates the status.
Mean Well is a member of KNX.
Click here for more information (datasheet of KNX-20E-640, pdf)