Since January 2016 the bus board is delivered with four connecting cables. For that reson it's compatible with the new switching power supply PSU3, which carries four secondary voltages (+12V, +5V, -12V and ground [GND]).
Of course it is also possible to connect this bus board with three cables only to older Doepfer power supplies which don't generate +5V.
blade connectors for the power supply's secondary voltages: +5V, +12V, GND and -12V
Fourteen 16-pin headers for connecting Eurorack modules.