KVM swith connection with docking station

Dell Latitude D620 laptop

Docking station model PR01X

KVM switch: Belkin 2 port USB with audio

 

When the KVM switch is connected directly to the laptop everything is fine. When I attach it to the docking station the video works, but the keyboard and mouse (both are USB) do not. When I press the Num Lock key the associated light does not come on. So it would seem that either no power is coming through or insufficient power is being supplied.