See the images above with descriptions below.

Top right are two typical under desk sets, up showing cables entering through the umbilical into the cable tray. Data and power are separated ensuring conformity to British Standards.  Power in delivered to the four-socket outlet conveniently locate under the work-surface in a basket.

Central processing unit (CPU) is shown retained in a simple under-desk sling. This lifts the processor from the floor helping to avoid knocks but also making it more accessible to the user.  This sling is probably one of the simplest forms of support. More secure units are available as well as locking devices, to complete boxes where CPU is completely secure. 

Umbilical attaching to a beam under a desk which brings  cables up to the horizontal cable tray.

Desk mounted power module conveniently places power where the user can easily access it. Often this is the “user accessible power” for chargers and other desk top items.  The under-desk power is then dedicated for IT requirements.